CHAPTER 32 Biodigital Orthodontics: Integrating Technology with Diagnosis 975

CASE STUDY 32-1—cont’d

C Final

D Initial x-rays

Initial model FIGURE 32-45, cont’d

Continued 976 CHAPTER 32 Biodigital Orthodontics: Integrating Technology with Diagnosis

CASE STUDY 32-1—cont’d

F Therapeutic model

G Setup

H Final x-rays FIGURE 32-45, cont’d CHAPTER 32 Biodigital Orthodontics: Integrating Technology with Diagnosis 977

CASE STUDY 32-1—cont’d

A Initial

B Therapeutic FIGURE 32-46 A–F, Mutilated dentition, Damon bracket system, 0.014-inch Damon copper- nickel-titanium (CuNiTi), followed by 0.16- × 0.22-inch CuNiTi AF 35°C lower wire and upper Sure- Smile prescriptive archwire 17- × 25-inch CuNiTi AF 35° C followed by 19- × 25-inch CuNiTi AF 35° C.

Continued 978 CHAPTER 32 Biodigital Orthodontics: Integrating Technology with Diagnosis

CASE STUDY 32-1—cont’d

C Final

D Initial model FIGURE 32-46, cont’d CHAPTER 32 Biodigital Orthodontics: Integrating Technology with Diagnosis 979

CASE STUDY 32-1—cont’d

E Therapeutic model

F Setup FIGURE 32-46, cont’d 980 CHAPTER 32 Biodigital Orthodontics: Integrating Technology with Diagnosis

REFERENCES 9. Balut N, Klapper L, Sandrik J, Bowman D. Variations in bracket placement in the preadjusted orthodontic appliance. Am J Orthod Dentofacial 1. Mah J, Sachdeva R. Computer-assisted orthodontic treatment: the Orthop. 1992;102(1):62–67. SureSmile process. Am J Orthod Dentofacial Orthop. 2001;120(1): 10. Cash A, Good S, Curtis R, McDonald F. An evaluation of slot size 85–87. in orthodontic brackets—are standards as expected? Angle Orthod. 2. Sachdeva R. Sure-Smile: technology-driven solution for orthodontics. Tex 2004;74(4):450–453. Dent J. 2002;119(7):608–615. 11. Matasa CG. Preadjusted appliances: one shoe fits all? (II) Can brackets 3. Sachdeva R, Frugé JF, Frugé AM, et al. SureSmile: a report of clinical alone make them … straight? Orthod Materials Insider. 1994;7(3). findings. J Clin Orthod. 2005;39(5):297–314. 12. Scholz R, Sarver D. Interview with an Insignia doctor: David M. Sarver. 4. Sachdeva RC. SureSmile’s promise: digital care solutions for the ortho- Am J Orthod Dentofacial Orthop. 2009;136(6):853–856. dontic industry. Orthod CYBER Journal. 2001. 13. Kanavakis G, Spinos P, Polychronopoulou A, et al. Orthodontic journals 5. JCO INTERVIEWS Dr. Rohit CL. Sachdeva on a total orthodontic with impact factors in perspective: trends in the types of articles and author- care solution enabled by breakthrough technology. J Clin Orthod. ship characteristics. Am J Orthod Dentofacial Orthop. 2006;130(4):516–522. 2000;34(4):223–232. 14. Saxe A, Louie L, Mah J. Efficiency and effectiveness of SureSmile. World J 6. Scholz R, Sachdeva RC. Interview with an innovator: SureSmile Chief Orthod. 2010;11(1):16–22. Clinical Officer Rohit C. L. Sachdeva. Am J Orthod Dentofacial Orthop. 15. Alford TJ, Roberts WE, Hartsfield JK, et al. Clinical outcomes for patients 2010;138:231–238. finished with SureSmile™ method compared with conventional fixed 7. Sachdeva R, Feinberg MP. Reframing clinical patient management with orthodontic therapy. Angle Orthod. 2011;81(3):383–388. SureSmile technology. PSCO NewsWire. 2009;2(1). Available at http:// 16. Sachdeva R, Aranha SL, Egan ME, et al. Treatment time: SureSmile vs www.pcsortho.org/newswire/March-09.cfm. conventional. Orthodontics (Chic.). 2012;13:72–85. 8. Hodge T, Dhopatkar A, Rock W, Spary D. A randomized clinical trial 17. Patel N. Linear Analysis of Anterior Root Resorption Utilizing Cone-Beam comparing the accuracy of direct versus indirect bracket placement. J CT: SureSmile Versus Conventional Edgewise. M.S. Thesis, University of Orthod. 2004;31(2):132–137. Oklahoma; 2010. PART SIX Orthodontic Retention and Posttreatment Changes 33

Stability, Retention, and Relapse

Donald R. Joondeph, Greg Huang, and Robert Little

OUTLINE History of Retention, 981 Theory 7: Corrections Carried out during Periods of Occlusal School, 981 Growth Are Less Likely to Relapse, 983 Apical Base School, 981 Theory 8: Arch Form, Particularly the Mandibular Mandibular Incisor School, 982 Arch, Cannot Be Permanently Altered with Appliance Musculature School, 982 Therapy, 983 Retention Theories Proposed Other Factors Related to Retention, 983 in the Literature, 982 Tooth-Size Discrepancies, 983 Theory 1: Teeth That Have Been Moved Tend to Return to Interproximal Reduction, 983 Their Former Position, 982 Growth Factors and Posttreatment Change, 984 Theory 2: Elimination of the Cause of the Malocclusion Third Molars, 984 Will Prevent Recurrence, 982 Duration of Retention, 984 Theory 3: Malocclusion Should Be Overcorrected, 982 Occlusal Adjustment, 984 Theory 4: Proper Occlusion Is an Important Factor in UW Postretention Registry: Lessons Learned, 984 Holding Teeth in Their Corrected Positions, 982 Clinical Applications of Retention, 989 Theory 5: Bone and Adjacent Tissues Must Be Allowed to Retention Appliances, 991 Reorganize around Newly Positioned Teeth, 982 Positioner in Retention Planning, 994 Theory 6: If the Lower Incisors Are Placed over Duration of Retention, 994 Basal Bone, They Are More Likely to Remain in Recovery after Relapse, 994 Good Alignment, 983 Summary, 995

A working definition of retention in relation to orthodontics the specific factors causing relapses.” Different schools of thought might be stated as follows: the holding of teeth in optimal aes- have existed over time, and present-day concepts generally com- thetic and functional positions. bine several of the following historic concepts regarding retention. The requirements for retention are often decided at the time of diagnosis and treatment planning. The correct problem list or diag- Occlusal School nosis, a logical treatment plan, and the timing of treatment must be Kingsley2 stated, “The occlusion of the teeth is the most potent directed toward achieving favorable aesthetics, ideal function, and, factor in determining the stability in a new position.” Many as much as possible, the permanent maintenance of these goals. early investigators3–18 agreed that proper occlusion was of pri- Incorrect diagnosis or treatment, on the other hand, can compli- mary importance in retention. cate the requirements for retention. For instance, gross expansion of the dental arches, severe changes in arch form, incomplete reso- Apical Base School lution of anteroposterior malrelationships, and incomplete correc- In the middle 1920s, a second school of thought formed section of dental rotations may require additional retentive measures. ondary to the writings of Axel Lundstrom,19 who suggested that the apical base was one of the most important factors in HISTORY OF RETENTION the correction of malocclusion and the maintenance of a corrected occlusion. McCauley20 also suggested that intercanine For many years, clinicians did not agree about the need for reten- width and intermolar widths should be maintained as origi- tion. Hellman1 said, “We are in almost complete ignorance of nally presented to minimize retention problems. Strang and 981 982 CHAPTER 33 Stability, Retention, and Relapse

Thompson21 further confirmed and substantiated this concept. the individual to be able to breathe. Dentofacial changes asso- Finally, Nance22 also noted that, “arch length may be perma- ciated with this functional alteration appear to become more nently increased only to a limited extent.” severe with age28 and are a challenge to diagnose accurately and to treat and retain successfully. This retention issue has been Mandibular Incisor School discussed by Lopez-Gavito and colleagues,31 who conducted a Grieve23 and Tweed24,25 suggested that the mandibular incisors long-term evaluation of patients with initial open bite maloc- must be placed and kept upright over basal bone to maximize clusions. Despite attempts to control posterior maxillary verti- their stability. cal changes during active treatment and retention, the authors of this study found that 35% of the patients with an initial open Musculature School bite had an open bite of 3 mm or more 10 years out of retention. Rogers26 introduced a consideration of the necessity of establishing proper muscular balance. Others corroborated his thoughts. Theory 3: Malocclusion Should Be Overcorrected Over time, orthodontists have come to realize that retention is A common practice of many orthodontists is to overcorrect not separate from active orthodontic treatment; rather, retention a Class II malocclusion into an edge-to-edge incisor relation- is part of treatment itself and must be included in treatment plan- ship. One must be aware, however, that an overcorrection such ning. Stability has become a primary objective in orthodontic as this could be the result of muscle memory, rather than the treatment; without it, ideal function, optimal aesthetics, or both achievement of a true skeletal or dental correction. The use of may be lost.27 Care must exercised to establish a proper occlusion prolonged Class II elastics, for instance, may produce a for- within the bounds of normal muscle balance and with careful ward postural displacement of the mandible, which is difficult regard given to the apical base, as well as to the relationship of the to detect until elastics have been discontinued long enough to maxillary and mandibular bases to one another. allow normal mandibular posture to return, emphasizing the need to check patients in the centric relation position. RETENTION THEORIES PROPOSED Overcorrection of a deep overbite is an accepted procedure by IN THE LITERATURE many clinicians. Satisfactory maintenance of overbite correction depends on the establishment of satisfactory correction, or over- The orthodontic literature describes many theories regarding correction, during active treatment, as well as retention appliances, retention. Some are presented here, along with supporting such as an anterior bite plate, designed to prevent vertical relapse. literature. One of the more common types of relapses is the tendency for a previously rotated tooth to attempt movement toward its Theory 1: Teeth That Have Been Moved Tend to Return to former position. Overrotation is not often practical, and, fur- Their Former Position27-29 thermore, little evidence exists that indicates its effectiveness in Investigators do not agree on the reason for this tendency. preventing a return to the initial position. Preventing the ante- Suggested influences include morphogenetic pattern of mus- rior teeth from erupting rotated in the first place is often pos- culature,30 apical base,31–33 transseptal fibers,34 and bone mor- sible by providing space for unimpeded eruption through the phology. Regardless of the reason, most clinicians agree that use of orthodontic expansion appliances or by early removal teeth should be held in their corrected positions for some time of primary teeth. As Reitan has stated, “The principle is that after changes are made in their position. Only a limited num- if the tooth had never been rotated initially, it would have less ber of individuals have suggested that retention is routinely not tendency to re-rotate at a later time.”38 Additionally, increased necessary.12,35 stability of corrected rotations through minor surgical procedures has also been suggested by Allen,39 Boese,40 Brain,41 and Theory 2: Elimination of the Cause of the Malocclusion finally, Edwards,42 who recommended transseptal fiberotomy. Will Prevent Recurrence22 Until more is known about the causative factors that are related Theory 4: Proper Occlusion Is an Important Factor in to particular types of malocclusions, little can be done regarding Holding Teeth in Their Corrected Positions their elimination. When obvious habits such as thumb or finger Fidler and colleages43 studied the long-term stability of well- sucking or lip biting contribute to a malocclusion, recogniz- finished Class II cases a mean of 14 years after the discontinuing them as etiologic factors is significantly easier. To improve ation of all retention appliances. The authors concluded that retention prognosis, however, identifying and preventing, as successful achievement of a good occlusion after active ortho- much as possible, the causative factors that contribute to the dontic treatment was very stable in the long term. In contrast, malocclusion are important. Norwick44 evaluated the long-term stability of cases in which One of the more insidious habits that operate against suc- the final orthodontic result was judged to be unsatisfactory. cessful retention is tongue posture and function, which results Norwick found a statistically significant relapse in overjet and in anterior and, occasionally, lateral open bites. The mere fact posterior dental relationships a mean of 14 years 8 months out that the patient has been directed along a course of tongue or of retention. When compared with successfully treated patients, speech therapy and is able to meet all the exercise requirements the unsuccessful sample exhibited changes in overjet and pos- of the therapist on conscious command does not guarantee cor- terior dental relationships that appear to be the result of inade- rection of this subconscious behavior pattern.36 In fact, several quate occlusal correction at the end of active treatment. investigators have suggested that open bite malocclusion may be attributable to mouth breathing, resulting from nasophar- Theory 5: Bone and Adjacent Tissues Must Be Allowed ynx obstruction that could result from anatomic blockage, aller- to Reorganize around Newly Positioned Teeth gic disease,28 or adenoid hyperplasia.37 Mouth breathing may In general, the orthodontist should use some type of fixed or also be habitual, which then necessitates a compensatory low removable retention appliance to maintain the achieved cor- anterior tongue posture and rotated mandibular position for rection. Historic evidence shows that the alveolar bone and CHAPTER 33 Stability, Retention, and Relapse 983

periodontal ligament around the teeth that have been moved are Theory 8: Arch Form, Particularly the Mandibular Arch, altered, and it takes considerable time before complete reorganiza- Cannot Be Permanently Altered with Appliance Therapy tion can occur. Some authors advocate fixed wire retainers (1) as Treatment should be directed toward maintaining the arch form permanent retention, whereas others suggest that retainers should presented by the malocclusion as much as possible.21 Nance22 have no positive fixation to allow for the natural functioning of reported that attempts to alter the mandibular arch form were teeth.37,45 Oppenhein46 argued that repair of tissues around the met with failure and recommended maintenance of the man- teeth more rapidly occurs if no fixed retention appliance is used. dibular arch form as a treatment objective. In 1944, McCauley20 Whether stability increases with prolonged retention is also stated, “Since these two mandibular dimensions, molar width difficult to determine as documentation and a control of vari- and canine width, are of such an uncompromising nature, one ables, such as cooperation, length of retention time, growth, might establish them as fixed quantities and build the arches and appliance design, make reaching valid conclusions difficult. around them.” Strang21 reiterated in 1946, “I am firmly con- Present-day orthodontic concepts consider tooth position to vinced that the axiom of the mandibular canine width may be result from a state of equilibrium between the muscular envi- stated as follows: The width as measured across from one canine ronment and the influence of the transseptal and periodontal to the other in the mandibular denture is an accurate index to fibers surrounding the teeth.47 the muscular balance inherent to the individual and dictates the Theory 6: If the Lower Incisors Are Placed over Basal limits of the denture expansion in this area of treatment.” Bone, They Are More Likely to Remain in OTHER FACTORS RELATED TO RETENTION Good Alignment According to this theory, direct attention should be paid to Tooth-Size Discrepancies the proper angulation and placement of the mandibular inci- A discrepancy in tooth size is an often-overlooked problem in sors.23,24,48–51 The difficulty in evaluating this theory is deter- retention. Ballard66 reported that 90% of the casts of the 500 mining whether incisors have been placed upright over basal patients he examined had tooth-size discrepancies. When maxil- bone. The term upright may be defined as perpendicular to the lary teeth are too large in relation to mandibular anterior teeth, the mandibular plane, plus or minus five degrees, or some other maxillary teeth must be in one of the following positions to com- specified angulation,to the occlusal or Frankfort horizontal pensate: (1) deeper overbite, (2) greater overjet, (3) combination planes. Specifying exactly where basal bone begins or ends with of deeper overbite and excess overjet, (4) crowded maxillary ante- a satisfactory method of quantification is also difficult.33,52–54 rior segment, or (5) tendency toward Class III posterior occlusion. In growing patients, the mandibular anterior segment may If the mandibular anterior teeth are too large in relation to exhibit a physiologic migration or eruption pattern in relation the maxillary anterior teeth, then compensations may include to the mandibular body in a posterior direction that is apart (1) end-to-end incisor relationship, (2) space in the maxillary from the intended orthodontic tooth movement.55–58 If the anterior segment, which may be closed through restoration, (3) mandibular anterior teeth are lingually moved during ortho- incomplete resolution of mandibular anterior crowding, or (4) dontic treatment, then one can hypothesize that this movement treatment of the maxillary posterior teeth to a mesial position, may be in harmony with the normal eruption of these teeth and relative to the mandibular buccal segments. that retentive care may be minimized.59 Estimating and evaluating these compensations is possible by fabricating a diagnostic setup or by using a mathematical formula Theory 7: Corrections Carried out during Periods of to determine the degree and location of a tooth-size discrepancy Growth Are Less Likely to Relapse between the maxillary and mandibular arches.67 Three-dimen- Orthodontic treatment therefore should be instituted, if possi- sional imaging allows a very precise means of direct tooth-size ble, when the patient is young and actively growing. Little direct measurement and resultant planning for inherent discrepancies. evidence exists to substantiate this theory, but it is plausible. If orthodontists are in any way able to influence the growth and Interproximal Reduction development of the maxilla or mandible, then certainly one Measurements from dental study models or digital images can may logically presume that this growth can be influenced only determine tooth-size ratios and the degree and location of a while the patient is growing.60–63 In 1924, Matthew Federspiel64 tooth-size discrepancy. When anterior tooth-size discrepancies said, “I am free to confess that we find it almost impossible to exceed 2.5 mm, a trial setup is usually indicated to evaluate the treat a true type of disto-occlusion without extraction after the anticipated final occlusion. If the teeth can only be satisfactorily developmental period and keep it in position.” When treatment occluded with interproximal reduction (IPR) in the setup, then depends on inhibition or an alteration of the growth direction, the clinician should include IPR of these same teeth in the mouth. as anticipated with headgear or functional appliances, both IPR can usually be accomplished with more control and ease fixed and removable treatment must be sufficiently initiated during the finishing stages of therapy. Approximately 2.5 mm early to utilize active growth. of enamel can be removed from the maxillary or mandibular Early diagnosis and treatment planning appear to afford sev- six anterior teeth (0.25 mm from each surface). To determine eral advantages with regard to long-term stability. The institu- the surface best reduced, the size and shape of the teeth are tion of early intervention can prevent progressive, irreversible considered in an attempt to correct any intraarch asymmetries tissue or bony changes,65 maximize the use of growth and devel- and to minimize gingival interproximal black triangles. Enamel opment with concomitant tooth eruption, allow interception thickness should also be considered through the use of accu- of the malocclusion before excessive dental and morphologic rate periapical radiographs. Removing excessive enamel from compensations occur (which may become more difficult to the contact point to the extent that the crown width becomes resolve) and allow correction of skeletal malrelationships while narrower than the cervical dimension should be avoided, since sutures are morphologically immature and more amenable to doing so will prevent closing of the spaces in a normal contact alteration. relationship, and incisor root proximity could occur. 984 CHAPTER 33 Stability, Retention, and Relapse

Growth Factors and Posttreatment Change The authors of this review indicated that most of the included Growth can be an aid in the correction of many types of ortho- studies had a high risk of bias, and they reported that most of dontic problems, but it may also contribute to changes in treated the studies did not indicate a relationship between third molars orthodontic cases. For instance, although orthodontists take and lower incisor crowding. However, they also stressed that advantage of growth when treating patients through growth the quality of the evidence on this topic prevented them from modification appliances such as headgear68 or fixed or remov- drawing any definitive conclusions. able functional appliances, alterations of the postorthodontic Implicating third molars as a cause of crowding is tempting. occlusion can occur, not through tooth change but through Some postulate that mesial drift plus third-molar eruption may disparate maxillary and mandibular growth. Progressive asym- be cofactors that cause the onset of incisor crowding. However, metric growth after treatment may also be demonstrated with many patients who have had third molars removed experience concomitant occlusal changes, despite successfully maintaining incisor crowding that progressively worsens.74 Similarly, many the teeth in their posttreatment positions. individuals who are congenitally missing third molars will With the possible exception of those who have an open- develop incisor crowding over time.74 bite malocclusion, patients who have a Frankfort mandibular angle (FMA) within the normal range can generally be expected Duration of Retention to show a reduction in this angle with continued growth. If, Does prolonged retention provide greater stability? A prior during orthodontic treatment, the FMA increases, then it may study indicates no consensus has been reached on how long to be expected to return to its former relationship, or less, if the use retention appliances.81 Also, to date, no satisfactory com- patient continues to grow. If no further growth takes place, then parisons have been made of patients with comparable malocclu- the return to the original FMA will likely not occur. If, however, sions similarly treated but having different retention protocols further growth occurs and the maxillary and mandibular teeth and durations. Most clinicians would consider “longer is bet- are retained in a position of minimal overbite, then the subse- ter” but recognize individual differences among patients. Long- quent increase in posterior facial height and a leveling of the term maturational changes are often confused with relapse and, FMA may occur without an accompanying increase or relapse in no matter what the label, may be attenuated with semiperma- the deep overbite. nent retainer wear. As a clinician, determining exactly how long Increases in the angulation of the occlusal plane to facial (hours, days, months, years) to use retainers after active treat- planes during orthodontic treatment are undesirable; the general ment and with what frequency is difficult. To complicate the tendency is for these angles to reverse or decrease after therapy. issue, accurately assessing the actual time of retainer wear by Class II mechanics, for instance, can rotate the occlusal plane in the patient is often difficult. In the absence of conclusive evi- a clockwise direction by extruding mandibular buccal segments, dence on the appropriate duration of orthodontic retention, the proclining and intruding lower incisors and extruding and concept of semipermanent retention may be the safest bet for uprighting the maxillary incisors. If no further growth is forth- a patient, as long as retainers continue to be monitored on a coming after the occlusal plane has been rotated in this manner, regular basis by the orthodontist and/or general practitioner. then the subsequent recovery change of the occlusal plane angle may mean the return of the original Class II buccal relationship Occlusal Adjustment also with a return of excess overjet as the dental changes reverse.69 Treatment objectives should include the basic principles of The implications of mandibular growth and latent man- gnathology such as canine disclusion and incisal guidance dibular growth in the true Class III malocclusion are very well whenever possible. Stability may be improved with occlusal known, and, accordingly, orthodontists do not usually attempt adjustment, concomitant with or after orthodontic treatment, to perform definitive treatment until all growth has ceased. that includes the removal of interferences in centric relation, as Removable functional appliances may play an important role well as cross-tooth and cross-arch deflective interferences not during retention to assist in maintaining the correction of skel- eliminated during orthodontic finishing. Attempts to achieve etal components. These types of removable appliances can be final functional balance immediately after the appliances are worn during sleep to minimize changes in the maxillomandibu- removed may not be desirable. The dental changes or settling lar relationship that may take place, secondary to unharmonious that naturally occurs after appliance removal should be taken growth. Functional appliances may also be an effective way to into consideration before undertaking extensive equilibra- encourage differential eruption and tooth movement in compen- tion procedures. Indeed, any occlusal adjustment in the first 6 sation for skeletal changes resulting from posttreatment growth. months after appliance removal should be solely performed to eliminate gross interferences. Restorations can be recontoured, Third Molars cusps and incisal edges adjusted, and teeth aesthetically recon- Third molars are often implicated as causing crowding of the toured where excessive wear or lack of function has produced mandibular anterior teeth in the late teens and early 20s. Some undesirable dental morphologic outcomes. Long-term consid- authors have attributed the presence of third molars to long- erations include periodic observation of posttreatment changes term mandibular dental instability,70–73 but others have pub- with possible detailed occlusal adjustment, as needed, to achieve lished data suggesting that third molars play little, if any, role in desirable and functionally beneficial results. long-term mandibular arch changes.74–77 Additionally, two systematic reviews address this issue. In UW POSTRETENTION REGISTRY: LESSONS LEARNED the earlier review by Mettes,78 one randomized trial79 was iden- tifiedfor inclusion in the review that indicated third molars did The idea for the postretention registry at the University of not have an impact on lower incisor crowding over a 5-year Washington (UW) should be credited to Dr. Richard Riedel period. In the more recent review by Zawawi,80 12 studies were (Fig. 33-1), former chairman of the Department of Orthodon- identified for inclusion, although only 3 were prospective trials. tics. As the story goes, Dr. Riedel wished to determine how his CHAPTER 33 Stability, Retention, and Relapse 985

American Board of Orthodontics cases held up many years after treatment. Upon collecting these records, he learned so much that he decided to increase the target population to all of his former patients. Later, Dr. Little joined Dr. Riedel in this effort, and they expanded the search to include cases from the graduate clinic, faculty practice, alumni, and other interested orthodontists. The result of this collaboration is a collection of approximately 900 cases that have follow-up records at least 10 years after the end of retention, that is, 10 years after all retainers have been removed or discontinued. This sample was not randomly collected nor was it consecutively chosen. Thus the potential for some selection bias is present. If these data could be collected again, then more emphasis would be given to the parameters for sample selection. However, Dr. Riedel tried to include all subjects who were willing to undergo the collection of long- term records, regardless of their long-term outcome. If there is bias, then it might be toward over-representation of patients who exhibited relapse; those who were stable may have had less reason to return to their orthodontists long-term. Neverthe- less, the size of the sample is impressive, and given the known FIGURE 33-1 Dr. Richard Riedel, founder of the postretention limitations of the observational data, this registry has certainly registry at the University of Washington, Seattle. assisted orthodontists in understanding the changes that occur in alignment and arch dimensions many years after treatment. As stated by Edward Angle82 himself, “The period of retention of teeth, after they have been moved into normal occlusion, is one of the most important in treatment, and so complicated and persistent are the delicate forces that tend to derangement A of the established occlusion as to necessitate the most thought- ful consideration of the problems involved, and a degree of skill in overcoming them which much experience alone can develop, even among those with talent for the work.” That statement was written over 100 years ago, and the orthodontic professionals B are still challenged by these same forces. As mentioned earlier, many theories have been proposed regarding retention and stability, such as occlusion, muscle balance, incisor proportions, the apical base width, and the placement of incisors over basal bone. Although all of these theories are interesting, the reality is that, today, orthodontists are still debating how to prevent teeth from moving after treatment. What lessons can be learned A = intercanine width about relapse emerge from the orthodontic postretention UW B = intermolar width registry? FIGURE 33-2 Arch width dimensions. 1. Postretention changes are unpredictable. Upon meeting a new patient, how often have we wished for a “crystal ball” to predict influences such as growth, treatment response, and cooperation? Having this knowledge in advance would certainly allow us to customize our treatment. The same could be said for retention—if only we knew in advance whose teeth would have a high-relapse potential and whose teeth would stay in their corrected positions. This knowledge would certainly AB allow us to tailor the types of retainers we prescribe, as well as the wear regimen. However, as helpful as these predictors could be, the hundreds of cases in the registry seem to indicate that postretention changes are unpredictable. Based upon intercanine and intermolar distances (Fig. 33-2), as well as arch length (Fig. 33-3) and the Irregularity Index scores (Fig. 33-4), predicting the long-term outcome based on the initial or end- of-treatment condition was difficult83 (Fig. 33-5). Therefore long-term retention seems to be the only predictable way to ensure a stable result. Even extraction cases, in which incisors are placed over basal bone, displayed only acceptable alignment A + B = arch length in approximately one third of the treated cases after 10 years,83 FIGURE 33-3 Arch length measurements. and by 20 years, this rate was down to 10%.84 Although many 986 CHAPTER 33 Stability, Retention, and Relapse cases relapsed toward the original pattern, this movement was 58% of the practitioners, and clear thermoplastic retainers were not always the case; we were sometimes surprised by teeth recommended by 30%. moving opposite of the original positions. 2. Arch length and width constrict over time, especially Of course, problems with long-term retention can occur intercanine width. Trends were noted in the postretention using fixed retainers. Oral hygiene can be difficult, and the pos- cases, and a particularly strong one was constriction in arch sibility for caries under or around the lingual retainers certainly dimensions, especially intercanine width (Fig. 33-6). This trend exists. Most orthodontists believe periodically checking these may be related to the popular notion in dentistry known as the retainers is their obligation to ensure that they do not become mesial drift, in which posterior teeth have a tendency to mesially loose. When they do loosen, relapse can sometimes occur migrate over time. Since the basal bone houses the roots and alarmingly quickly, perhaps faster than the patient can make an the lips and tongue provide a corridor for the crowns to exist appointment to have the retainer repaired. On rare occasions, in a state of equilibrium, mesial drift would eventually result twisted wires can remain bonded to the teeth but, through the in the crowding of the front teeth, especially the lower incisors. relaxation or distortion of the wire, express torque can cause Thus to the extent possible, attempting to maintain or decrease roots or crowns to move considerable distances. intercanine width seems prudent. In patients with mandibular Given these limitations, bonded lower retainers are still a incisor crowding, aligning the incisors will always result in an more reliable choice for long-term retention than removable increase in intercanine width and/or protrusion unless IPR or retainers, which are notorious for being lost, thrown away, bro- incisor extraction is performed. Even extraction of premolars ken, and inadequately used. A study published in 2010 reported cannot prevent an increase in intercanine width unless the above that 40% of orthodontists are routinely prescribing lower fixed conditions are met, as the canines are moving into a wider area retention, whereas 28% prescribe Hawley retainers (DDS Lab, of the arch to allow alignment of incisors (see Fig. 33-6). Thus, in Tampa, FL) and 18% recommend clear thermoplastic retain- reality, alignment without an increase in intercanine distance is a ers.85 In the maxillary arch, Hawley retainers were prescribed by difficult task to accomplish, and we must be prepared to deal with the arch constriction that almost inevitably follows.83 Further complicating our understanding, not all cases show intercanine C D constriction after retention, a few actually show expansion. A B E Using the UW sample, investigators assessed the stability of cases undergoing lower incisor extraction. Interestingly, these cases seemed to exhibit better incisor irregularity scores long- term, compared with other types of extraction and nonextraction samples.86 One might argue that incisor irregularity scores should be lower with incisor extraction cases, since they have fewer contacts to count. However, the investigators controlled for this factor by calculating an average of the incisor irregularity scores; the lower scores were still significant. As previously mentioned, incisor extraction is one of the few treatment modalities we have that can actually allow a reduction in intercanine width, and perhaps this reduction plays a role in the improved stability. In recent decades, arch expansion using various techniques A + B + C + D + E = irregularity index has become a popular method to address crowding. In partic- FIGURE 33-4 Calculation of the Irregular Index score. ular, claims have been made that treatment with self-ligating brackets allows bone development and, subsequently, better stability. However, little scientific evidence indicates that these 12 claims are true. Although the long-term cases in the UW reten- N = 61 tion registry were not treated with self-ligating brackets, their r = .20 10 p = N. SIG. results indicate that patients undergoing arch development may be among the most unstable cases encountered.87 Whether the arch development was in the transverse and/or in the anterior 8 dimension, these patients’ arches tended to relapse significantly when retention was discontinued. 6 3. Rotations usually relapse toward initial positions. If teeth relapse, then predicting that they will relapse toward their original positions seems logical. One philosophy of treatment to 4 counteract this relapse potential is called 11/10 orthodontics,88 in which teeth are overcorrected by approximately 10% in rotations or labial and/or lingual movement. The idea is 2 POSTRETENTION IRREGULARITY that when the tooth relapses, the 1/10 overcorrection will be lost, leaving the tooth in the correct position. Unfortunately, 0 predicting the amount and direction of relapse has proven 0510 15 20 to be difficult. Although some teeth, perhaps the majority, PRETREATMENT IRREGULARITY relapse toward their original position, approximately 20% of FIGURE 33-5 Relationship between pretreatment irregularity teeth unexpectedly relapse away from their original position,89 and postretention irregularity. making it very difficult to decide whether overcorrection will CHAPTER 33 Stability, Retention, and Relapse 987 be harmful or detrimental (Fig. 33-7). Some have advocated and thought of undergoing surgery can be unpopular, especially a supracrestal fiberotomy to assist with preventing relapse, if stability is not guaranteed. and some research suggests that this surgical technique can To prevent relapse of lower incisors, lingual bonded retain- be effective.37,42 For teeth that have undergone a fiberotomy, ers are very common. The two styles that are commonly used there is no guarantee that rotational relapse will not occur. The are either bonded only to the canines or bonded to each ante- primary point is that the degree of rotational relapse is lessened rior tooth. Although not bonding to incisors that were normally but not fully eliminated after fiberotomy. Additionally, the cost positioned at the pretreatment phase has advantages for oral

FIGURE 33-6 Photographs of constriction of mandibular intercanine dimension, from ages 12 years 10 months, 15 years 6 months, and 27 years 2 months.

Initial Final

Long-term

FIGURE 33-7 Photographs of 11/10 orthodontics, as the potential for rotations to move away from the pretreatment condition. 988 CHAPTER 33 Stability, Retention, and Relapse hygiene, any incisors that are not bonded can sometimes move Three approaches might be taken. The first strategy is early labially or lingually or rotate, even though lip pressure should expansion or arch enlargement. There are some who advocate generally prevent this movement from happening (Fig. 33-8). early expansion to address arch length issues.91 However, Retainers bonded to each anterior tooth will prevent posttreat- early expansion is not immune from relapse. In fact, patients ment movement, but hygiene can be more difficult, and more undergoing mixed dentition enlargement of the lower arch bonds are there to possibly fail. showed the poorest postretention results in our sample, with 4. Some cases will display more favorable results. A group only 10% having acceptable long-term results.87 of patients that seem to fare better than most are the ones who A second strategy is serial extraction. Unfortunately, this have adequate or excess arch length at pretreatment (Fig. 33-9). technique does not appear to have a better long-term outcome It seems intuitive that those with more than enough space are less than premolar extraction in the permanent dentition.92 Per- likely to crowd in the long term. These patients probably have haps the reason for this is that patients are candidates for serial large jaws, small teeth, or a combination of the two, and either extraction because they have insufficient arch length at an early factor provides a considerable advantage for the maintenance age and are destined for recrowding after treatment and reten- of long-term alignment. Additionally, patients with adequate or tion, just as are most patients with crowded full dentition. excess arch length have the benefit of maintaining or decreasing Orthodontists have hypothesized that those serial extraction their intercanine width during orthodontic treatment, similar to cases who demonstrate self-improvement of alignment during the the incisor extraction cohort. One long-term study demonstrated observation period and before full treatment will likely be more that these patients rarely showed more than mild crowding.90 stable after retention. Unfortunately, this theory has not proven to 5. Early treatment may not improve long-term stability. be true. Those who favorably react during the observation period One may ask whether the management of crowding at a may or may not significantly relapse after retention, just as those younger age is associated with better long-term stability. who do not fare well during the observation period may or may not do well after retention. Serial extraction outcomes seem to be unpredictable in influencing alignment in the long term. A third approach is utilizing the leeway space. Hayes Nance advocated this strategy, and, in fact, some evidence suggests that utilizing the leeway space may result in superior long-term outcomes.93 Probably, however, patients who are candidates for preserving leeway space are not as crowded as those who undergo serial extraction; thus the initial crowding should be considered when assessing the long-term outcomes of patients undergoing serial extraction versus the utilization of the leeway space. If the leeway space is equal or greater than anterior crowding, then this strategy appears to give good results. FIGURE 33-8 Photograph of an incisor moving away from If the leeway space is insufficient to permit anterior alignment a retainer only bonded to the canines. (Brackets were placed without expansion, then this strategy will likely fail to improve immediately before taking this photograph.) retention.

FIGURE 33-9 Photographs of good alignment over a 13-year period in a patient with pretreatment spacing (red dotted lines). CHAPTER 33 Stability, Retention, and Relapse 989

6. Early postretention stability is usually a mirage. poor finishes tended to show some long-term improvement Many of our patients with fixed retainers displayed a period of in the scores from the American Board of Orthodontics relative stability after the removal of retainers. However, this objective grading system (ABO-OGS).95 Although this finding stability proved to be short lived; after a few years, more and more might seem counterintuitive, the fact that patients with the crowding occurred. One might wonder when the relapse ceases. best ABO-OGS scores have little room to improve should be Following cases from 10 and 20 years after retention, apparently, given consideration. On the other hand, patients with poor there is no end point. The rate of relapse seems to slow in these ABO-OGS scores tended to improve in several areas, including cases, but slow, undesirable alignment changes continued to marginal ridges, buccolingual inclination, and occlusal happen.84 Some patients seemed to have a period of accelerated contacts. However, one additional important finding was that tooth movement immediately after the fixed retainers were the cases with the best finishes had the best long-term ABO- removed. For patients with a strong relapse tendency, many OGS scores, indicating that high-quality treatment does, in fact, years of fixed retainers may not be enough. Unfortunately, once provide long-term benefits, compared with that of lesser quality a bonded retainer is placed, the only way to test stability is by treatment. removing the retainer. A graduated lessening of retainer use, Feeling a little discouraged after reading the findings of the which can be done with removable retainers, is not an option. UW postretention registry is natural. Many of our patients did 7. Life-long retention is the best insurance policy. If there not hold up well in lower anterior alignment 10 or 20 years is a common theme to our long-term findings, then it is that life- after discontinuing retainer wear. Certainly, after all the effort long retention is the best insurance policy that can be provided to of straightening teeth and correcting occlusions, it would be a patient. Of course, it is probably not realistic to expect patients to ideal if teeth would remain in stable positions. However, we are wear their retainers forever. Removable retainers can be lost, worn reminded that our bodies undergo changes during our entire out, and forgotten, and fixed retainers eventually become loose. lifetimes; perhaps the concept that a perfect occlusion will be Perhaps one strategy is to enlist patients to become partners in the stable is unrealistic. In fact, some have proposed using the term retention process. After all, they will quickly learn if their teeth have physiologic maturation or normal aging rather than relapse to a tendency to move or shift, especially if they are using removable describe the changes that occur after treatment. retainers. Retention visits should provide an opportunity to Of course, we should strive for excellence, as the study by discuss retainer use and any observed relapse in a candid and Nett and Huang95 indicates that better occlusions will, on aver- cooperative fashion and to transfer ownership of posttreatment age, exhibit better alignment in the long term. However, above changes to the patient. Fixed retainers usually limit changes in the all else, perhaps we need to have candid and honest discussions lower arch; however, when removable retainers are used, patients with our patients before initiating treatment to ensure that they must be told that they should use their retainers as much as needed will understand the importance of retainers. Patients should to maintain tooth position. Letting patients know that they are in also understand that, despite the best efforts of orthodontists, charge and that you will provide assistance can be helpful. Then, teeth will and do move, change, and shift over time in somewhat when posttreatment movements do occur (and they will for most unpredictable ways. Additionally, we also should acknowledge patients), offering retreatment options and letting patients decide that our understanding of retention is less than perfect. In fact, how they would like to proceed are both significantly easier. a Cochrane systematic review published in 2006 concludes that, 8. Extraction of third molars is not necessarily helpful “There are insufficient research data on which to base our clin- to prevent crowding. One of the most common retention ical practice on retention at present.”96 questions that orthodontists hear is whether third molars will cause crowding when they erupt, ruining the results of CLINICAL APPLICATIONS OF RETENTION orthodontic treatment. Third molars often appear during the time that lower incisor relapse occurs, and ascribing the Retention planning will divided into three categories, depending crowding to the eruption of the third molars is only natural. on the type and extent of retention treatment instituted: (1) lim- However, the best evidence to date, which comes from two ited retention, (2) moderate retention in terms of time and appli- systematic reviews,78,80 indicates that third molars do not seem ance wearing, and (3) permanent or semipermanent retention. to play a large role in lower anterior crowding. In fact, even I. Limited retention required. those with third molars removed or congenitally absent develop A. Corrected crossbites lower anterior crowding in the late teenage years and in the 1. Anterior: when adequate overbite has been estab- early 20s.74 Coincidently, the typical age of third molar eruption lished seems to happen when active relapse begins to occur, even for 2. Posterior: when axial inclinations of posterior teeth those who have congenitally absent third molars. Nevertheless, remain reasonable after corrective procedures have this urban myth has proven extremely difficult to dispel, even been completed. An exception is posterior crossbites among general dentists, oral surgeons, and orthodontists. treated with either orthopedic or surgical expansion 9. Here is some good news—maxillary teeth fare better. of the midpalatal suture. In these cases, overcor- There are some positive findings from the UW retention registry. rection and long-term retention are desirable. It appears that relapse occurs for the upper incisors to a lesser B. Dentitions that have been treated by serial extraction. degree, and, in addition, the upper incisors do not necessarily The percentage of complete satisfaction secondary to mirror the alignment changes observed in the lower arch.94 extraction and autonomous eruption alone is typically 10. Treat to excellence. Quality matters! There were also rather low and depends on the degree of perfec- some interesting findings concerning finishing cases to the tion desired by the patient and orthodontist. When highest standards. A study investigating changes in patients with extraction of the mandibular second premolars is pos- varying degrees of excellent to poor final results showed that an sible or when they are congenitally absent, the resul- overall regression to the mean long term occurred; that is, cases tant occlusions often are more satisfactory than those with excellent finishes tended to deteriorate, whereas cases with in first premolar serial extraction cases.97 990 CHAPTER 33 Stability, Retention, and Relapse

C. High canine extraction cases. that growth is complete. This seems to suggest that D. Cases calling for extraction of one or more teeth such correction of deep overbites is desirable before the as subdivision types of malocclusions, or when the completion of facial growth. The work of Matthews posterior teeth are in Class II relationship and the in this field concludes that beneficial results may be anterior teeth are treated to a Class I canine position. achieved by beginning overbite correction as early as Occasionally, lingual bonded retainers can be used to the primary or mixed dentition. prevent extraction spaces from opening. Severe occlusal plane tipping also may require E. Corrections that have been achieved by retardation of extended retention protocols and possibly additional maxillary growth after the patient is through growing. maxillary restraint as well. Examination of cephalomet- F. Dentitions in which the maxillary and mandibular ric films taken at about 6-month intervals will reveal teeth have been separated to allow for eruption of teeth whether adaptive growth changes have taken place.101 previously blocked out. Typical examples are partially D. Early correction of rotated teeth33,38 to their normal impacted mandibular second premolars and maxillary positions. canines. 1. Perhaps before root formation has been completed II. Moderate retention required. 2. In the mandibular incisor area, a fixed lingual or A. Class I nonextraction cases, characterized by protru- removable type of appliance with a labial bow is sion and spacing of maxillary incisors. These cases probably best. In this area the occlusal splint-type require retention until normal lip and tongue function or Hawley spring retainer may be useful (Fig. 33-10). has been achieved. More recently, gingivectomy procedures have B. Class I or Class II extraction cases probably require that offered hope for increased stability of corrected the teeth be held in contact, particularly in the maxillary rotations. Early correction of rotations, transeptal arch, until lip and tongue function can achieve a satis- fiberotomy and long-term fixed retention may factory balance, as in the nonextraction group. Especially prove to be the most satisfactory.39–42,46 true in extraction cases is that the maxillary incisors can be E. Cases involving ectopic eruption of teeth or the presence retracted so far as to be unrestrained by lip pressure and of supernumerary teeth require varying retention times, to impinge on the space occupied by the tongue before usually prolonged, and occasionally a fixed or perma- treatment. Use of a maxillary removable retainer until nent retentive device, such as bonded lingual retainers. normal functional adaptation has occurred generally 1. Supernumerary teeth may be encountered in the is desirable. The time of application of this type of reten- maxillary anterior area and, on removal of these tion can be reduced as the patient adapts to new tooth teeth, the maxillary incisors often erupt slowly and positions, proceeding from full-time wearing of appli- incompletely. When the latter have been brought ances to nighttime wear only, then perhaps every other to a normal level through orthodontic therapy, night, once or twice a week, and finally wearing retain- bonded lingual wires are desirable because these ers at night as needed when they feel tight on insertion. teeth seemingly have a tendency to reintrude when Corrections of adult dentitions probably require longer released. Palatally impacted canines, once brought retentive procedures. A predetermined time schedule into arch alignment, also may benefit from fixed for removing retentive appliances probably is undesir- lingual retention wires bonded to adjacent teeth to able in these cases, and the time of retention depends prevent reintrusion and palatal relapse (Fig. 33-11). directly on the patient ‘s compliance and reactions 2. Excessive spacing between maxillary incisors during retention. Tongue and myofunctional therapy requires prolonged retention after space closure. may be advantageous in this group of corrected cases. F. The corrected Class II, Division 2 malocclusion gener- C. Corrected deep overbites in Class I or Class II malocclu- ally requires extended retention to allow for the adap- sions usually require retention in a vertical plane.98–100 tation of musculature. These cases, because they are 1. If anterior teeth were depressed to achieve overbite correction, a bite plate on a maxillary retainer is desirable. To be effective in retaining overbite correction, the bite plate should be worn continuously for perhaps the first several months, including while the patient is eating. In deep overbite cases, overcorrection is usually desirable and occlusal adjustment to an ideal functional relationship is a consideration. 2. If overbite correction was achieved as a result of clockwise mandibular rotation, vertical dimension should be held at least until growth of mandibular ramal height catches up and neuromuscular balance can adapt. A measure of bite opening can be assessed in the degree of change between the mandibular plane and a cranial base plane, such as the Frankfort or sella- nasion. Positive changes of the mandibular plane FIGURE 33-10 Mandibular splint retainer. Wire position can be angle suggest continued retention until growth altered to avoid passing through an extraction site or coming in compensates or until the orthodontist determines contact with the maxillary dentition. CHAPTER 33 Stability, Retention, and Relapse 991

typically treated without extractions, generally undergo some increase in mandibular intercanine width and present with malalignment of maxillary incisors, which needs to be maintained during retention. III. Permanent or semipermanent retention required. A. Cases in which expansion has been the choice of treatment, particularly in the mandibular arch, may require permanent or semipermanent retention to maintain normal contact alignment. In many instances, patients have aesthetically desirable dentofacial relationships, and extraction of permanent teeth would create aesthetically undesirable results. The orthodontist may be faced FIGURE 33-11 Lingual bonded retainers designed to prevent with a choice between stability and aesthetics, and often relapse of canines that were initially palatally impacted. A the patient’s aesthetic requirements take precedence. removable retainer is made to fit over and/or around the sec- B. Cases of considerable or generalized spacing may tional wires to retain tooth position in other planes of space. require permanent retention after space closure has been completed. C. Instances of severe rotation, particularly in adults, or severe labiolingual malposition may require permanent retention, as provided by lingual bonded retainers. D. Spacing between maxillary central incisors in otherwise normal occlusions sometimes requires permanent retention, particularly in adult dentitions (Fig. 33-12).

RETENTION APPLIANCES The Hawley retainer9 (DDS Lab, Tampa, FL) is one of the most frequently used retentive appliances available to the clinical orthodontist. The palatal or lingual portion is usually constructed of acrylic and may completely cover the palatal mucosa or can be constructed in a horseshoe shape contacting the lin- FIGURE 33-12 Lingual bonded 0.014-inch stainless steel wire is gual surfaces of the teeth and only a limited amount of palatal applied to hold midline diastema from relapsing. Care should be mucosa. A labial bow of round stainless steel 0.020- to 0.036- taken to keep retainer out of occlusion with mandibular incisors. inch wire is usually constructed to contact the labial surfaces of

FIGURE 33-13 Typical Hawley and splint retainers. The models should be articulated in occlusion to ensure that the patient is not prematurely contacting on retainer wires or acrylic unless an anterior bite plate is desired. The maxillary labial bow may also cross the occlusion at the canine-lateral incisor embrasure with distal clasping of the canine to avoid a wire in the extraction site that might inadvertently aid reopening of the contact. 992 CHAPTER 33 Stability, Retention, and Relapse four or six maxillary anterior teeth (Fig. 33-13). Constructing Pontics may be included in the retainer design to enhance the wire to cross incisally through the contact area between the aesthetics and to retain the edentulous area(s) during the tran- canine and the lateral incisor may minimize occlusal interfer- sition from fixed appliances to prosthetic replacement of miss- ence in the area of the mandibular canine. If such construction ing teeth (Fig. 33-16). Lingual bonded segmental wires are used is used, then inclusion of a restraint on the labial aspect of the to prevent the teeth from drifting into the edentulous areas, and canines is desirable to prevent their extrusion or labial drift. a flipper with pontic(s), which is made to fit over the bonded The clinician may wish to alter the type and position of wires, is worn during the day for aesthetics (Fig. 33-17). After retention clasps to avoid traumatic occlusal interferences and the placement of the implants, the retainer can be relieved in to assist in eruption guidance or minor tooth movements, such the gingival area to allow maintenance of dental aesthetics while as erupting second molars (Fig. 33-14). Additionally, the labial avoiding tissue impingement during the osseointegration stage. bow and retention clasps should not pass through extraction The clinician may adjust the retainer after completing the pros- sites, if possible, because that may encourage the tendency for thetic phase simply by removing the pontic and recontouring the space to reopen, especially in adult patients. the palatal acrylic to fit the final restoration. Circumferential maxillary retainers provide excellent retention with the added benefits of eliminating potential occlusal interferences and aiding in holding the space closed (Fig. 33-15). The clinician may place keeper wires between the lateral incisors and canines or flow acrylic on the wire facial to the maxillary anterior teeth to enhance the stability of the labial wire. The clinician also can efficiently adjust labial bow tension if recurved loops are included. Palatal acrylic should be distally extended to retain second molar position, which is particularly important in patients who have undergone changes in transverse dimension during active treatment, such as maxillary surgical or orthopedic sutural expansion.

FIGURE 33-16 Maxillary circumferential retainer with pontic is applied to replace missing right central incisor.

FIGURE 33-14 Maxillary Hawley retainer with C clasps is applied to guide second molar eruption.

B FIGURE 33-17 A, Maxillary flipper with pontic to replace right lateral incisor is worn during the day for aesthetics. The flipper is made to fit over and/or around sectional wires bonded on the lingual side to prevent teeth from drifting into edentulous areas. FIGURE 33-15 Maxillary circumferential retainer. Palatal acrylic B, Flipper is in place for aesthetic replacement of the maxil- can be reduced to minimize effects on speech and swallowing lary right lateral incisor. Note the use of pink acrylic gingivally to patterns. Closing loops allow adjustment of tension. blend into oral mucosa. CHAPTER 33 Stability, Retention, and Relapse 993

A clear removable retainer with pontic(s) held in place of segmental retainers that splint two or more teeth together within the plastic is also typically made to be worn at night or to maintain intraarch tooth position. The wires used for such for use in emergency situations if the regular retainer is lost or retainers should be flexible (0.0175-inch twisted or 0.014- to broken. The clear retainer is stronger and acts as a night guard 0.016-inch stainless steel) to allow physiologic tooth movement. to prevent breakage of the pontic from grinding or clenching Bonded retainers may also be effectively used to hold extraction teeth during sleep (Fig. 33-18). spaces closed if relapse is anticipated (Fig. 33-22). Canine-to- Clear retainers are commonly used and have the ben- canine bonded retainers can also be distally extended to include efits of excellent aesthetics, broad tooth contact to hold premolars if the premolars were initially ectopic or if holding the alignment, and function as a night guard for those patients extraction spaces closed is the intent, as in adult extraction cases who exhibit mild to moderate parafunction such as clenching (Fig. 33-23). The clinician can also fabricate removable retainers or grinding teeth while sleeping (Fig. 33-19). These clear retainers are best adjusted or ground into occlusion to ensure even contact throughout the arches in centric relation occlusion. The clinician also may alter the size of a retainer to accom- modate special needs. A mandibular spring retainer, for instance, may include only six or eight anterior teeth to eliminate the difficulty of seating such an appliance over buccal segment undercuts, which are fairly common in adult patients with long clinical crown heights or undercuts created by excess lingual crown torque or restorations (Fig. 33-20). The clinician may also use fixed retention appliances to retain potential areas of relapse more securely and to reduce the dependency on patient compliance (Fig. 33-21). The development of bonding materials has facilitated the fabrication

FIGURE 33-20 Mandibular spring retainer modified to maintain only anterior tooth position.

FIGURE 33-18 Clear retainer with the maxillary right lateral incisor pontic used during appliance therapy transferred and included in the retainer.

B FIGURE 33-21 A, Mandibular bonded retainer. A braided wire is bonded to each tooth but allows physiologic tooth movement. B, A maxillary bonded retainer may also be placed to prevent relapse of initial spacing or irregularity. This retainer must be positioned and contoured to prevent premature mandibular FIGURE 33-19 Example of clear maxillary overlay retainer. incisor or canine contact. 994 CHAPTER 33 Stability, Retention, and Relapse

FIGURE 33-24 Diagnostic setup completed on an adjustable articulator after a facebow transfer. Fabrication of the positioner on this type of instrument allows the patient to bite into the positioner without altering condylar position.

FIGURE 33-22 Sectional wire bonded on the lingual to hold an muscle balance. The positioner is probably contraindicated in extraction site closed. patients who have a tendency for nasal airway obstruction and are mouth breathers because of the difficulty of breathing with a positioner in place. If a positioner is to be used on what has been a deep overbite malocclusion, then construction of a maxillary retainer with a bite plane to be used when the patient is unable to wear the positioner is a beneficial adjunct. Construction and placement of a positioner that fits over a fixed appliance, such as a lingual bonded retainer, are also considerations. Positioner setups and fabrication should be done on an adjustable articulator after a facebow transfer (Fig. 33-24) to allow the patient to function into the positioner without altering condyle-fossa relationships. FIGURE 33-23 Mandibular bonded retainers can be designed to extend distally to include premolars if premolars were initially DURATION OF RETENTION ectopic or to hold extraction sites closed. As noted from the literature, various authors suggest retention protocols that range from no retention whatsoever35,83 to permanent retention. Most clinicians will institute some to fit over bonded retainers to minimize potential relapse in the form of mandibular retention until completion of growth other planes of space and to maintain interarch relationships. is evident. The indefinite use of retainers should also be Studies102,103 conclude that fixed bonded retainers are as strongly considered, as needed, to ensure the maintenance dentally and periodontally healthy as wearing removable retain- of tooth relationships in the long term. The clinician should ers if they are maintained with proper oral hygiene techniques. discuss retention procedures with patients before starting The clinician can consider, however, eventually removing fixed orthodontic treatment to impress upon them the importance retention and fabricating removable retainers to be used as of the retentive phase that follows active treatment. Reten- needed to minimize the impact of long-term relapse and mat- tion may be described as a 12-month healing phase, during uration changes. which the newly made movements of teeth are stabilized, and a maintenance phase, to guard against the maturational POSITIONER IN RETENTION PLANNING changes in tooth position that occur over time. The latter phase is, of course, long term. The positioner appears to be particularly beneficial in reestab- lishing normal tissue tone and firmness where gingival hyper- RECOVERY AFTER RELAPSE plasia has occurred during treatment. The advantages of a positioner are that it is clean and unlikely to be broken, tends If, despite the utmost care in treatment and retention, relapse or to stimulate tissue tone, and constantly works toward main- further postorthodontic maturational change occurs, then the taining or improving tooth position. The disadvantages are its following suggestions may be useful: limited time of wear, because the patient can neither eat nor talk 1. Retreatment may take the form of rebanding or rebonding with the positioner in place, and the possibility that it may keep some or all teeth. Admittedly, this measure is extreme, but teeth loose by producing intermittent forces contrary to natural it may be necessary to accomplish the desired correction. CHAPTER 33 Stability, Retention, and Relapse 995

A B

FIGURE 33-25 Maxillary (A) and mandibular (B) spring retainers. Incisors have been realigned in the working model.

Permanent and long-term retention is likely preferable after REFERENCES retreatment. In any case, discovering and eliminating the factors that appear contributory to the relapse should be 1. Hellman M. Fundamental principles and expedient compromises in attempted. orthodontic procedures. In: Transactions of the American Association of 2. The mandibular lingual arch admirably serves to realign Orthodontists. St. Louis: Mosby; 1945. 2. Kingsley N. A Treatise on Oral Deformities as a Branch of Mechanical teeth in instances of mandibular collapse or crowding. Light Surgery. New York: Appleton & Co.; 1880. pressure against the mandibular anterior teeth may be used 3. Case CS. Retention of dental orthopedia. In: A Practical Treatise on the to realign them. In this situation, a removable lingual arch Principles of Dental Orthopedia and Prosthetic Correction of Cleft Palate. that facilitates adjustment and recontouring is an advantage. Chicago: CS Case; 1921. 3. Springs and clasps can be added to removable retainers to 4. Dewey M. Practical Orthodontia. St. Louis: Mosby; 1920. assist in repositioning and controlling labiolingual deviations. 5. Dewey M. Some principles of retention. Am Dent J. 1909;8:254. 4. Spring retainers using facial and lingual acrylic for added 6. Lischer BE. Orthodontics. Philadelphia: Lea & Febiger; 1912. leverage or clear aligners may be used for realignment. 7. Guilford SH. Orthodontia. Philadelphia: Spangler & Davis; 1893. Teeth are sectioned and aligned as in a diagnostic setup or 8. Baker HA. Discussion of Dr. Pullen’s paper. Dent Items Interest. aligned on a computer simulation and the active retainer 1907;29:389. 9. Hawley CA. A removable retainer. Dent Cosmos. 1919;61:449. or aligner(s) is(are) fabricated to the realigned relationship 10. Jackson VH. Orthodontia and Orthopedia of the Face. Philadelphia: JB (Fig. 33-25). The same spring retainer(s) used for align- Lippincott; 1904. ment can be used to maintain the achieved correction. Inter- 11. Markus MB. A review and consideration of the problem of retention. Am proximal stripping is sometimes beneficial as determined by J Orthod Oral Surg. 1938;24:203. the diagnostic wax-up or computer simulation. 12. Mershon JV. The removable lingual arch appliance. In: The First Interna- 5. A headgear or functional appliance may be used against tional Orthodontic Congress. St. Louis: Mosby; 1972. the maxillary arch during growth to provide maintenance 13. Northcroft G. The problem of retention with a view to permanence of or recorrection in instances of relapse toward a Class II result and minimum of danger. Br Dent J. 1915;36:898. relationship. 14. Ottolengui R. Discussion of Dr. Pullen’s paper. Dent Items Interest. 6. Habit training in the form of myofunctional therapy may be 1907;29:388. 15. Pullen HH. Some considerations in retention. Dent Items Interest. beneficial when abnormalhabit patterns have contributed to 1907;29:287. orthodontic relapse. Removable appliances are also helpful 16. Salzmann JA. Principles of Orthodontics. Philadelphia: JB Lippincott; 1943. as tongue restraints and trainers. 17. Simons ME, Joondeph DR. Change in overbite: a ten-year postretention 7. Occlusal adjustment and interproximal tooth size reduction study. Am J Orthod. 1973;64:349–367. may be a consideration to achieve an optimal aesthetic and 18. Thorne NAH. Experiences on widening the median maxillary suture. Eur functional result. Interproximal reduction (IPR) or strip- Orthod Soc Trans. 1956;32:279. ping in the crown width may reduce the tendency for further 19. Lundström A. Malocclusions of the teeth regarded as a problem in con- relapse. nection with the apical base. Int J Orthod Oral Surg. 1925;11:591. 8. In certain cases, the clinician may even suggest that the 20. McCauley DR. The cuspid and its function in retention. Am J Orthod. patient accept minimal relapse rather than continue with 1944;30:196–205. 21. Strang RHW, Thompson WM. Textbook of Orthodontia. 5th ed. Philadel- prolonged retreatment and retention. phia: Lea & Febiger; 1958. 22. Nance H. The limitations of orthodontic treatment; diagnosis and treat- SUMMARY ment in the permanent dentition. Am J Orthod. 1947;33:253–301. 23. Grieve GW. The stability of the treated denture. Am J Ortho Oral Surg. Retention is not a separate problem but is and will continue to 1944;30:171–195. be a problem to be considered during the initial and ongoing 24. Tweed CH. Why I extract teeth in the treatment of certain types of mal- diagnosis and treatment planning for patients. As Oppenheim46 occlusion. Alpha Omegan. 1952;46:93–104. so aptly stated, “Retention is one of the most difficult problems 25. Tweed CH. Indications for extraction of teeth in orthodontic procedure. in orthodontia; in fact, it is the problem.” Am J Orthod Oral Surg. 1944;30:405–428. 996 CHAPTER 33 Stability, Retention, and Relapse

26. Rogers AP. Making facial muscles our allies in treatment and retention. 55. Baum AT. Orthodontic treatment and the maturing face. Angle Orthod. Dent Cosmos. 1922;64(7):711–730. 1966;36:121–135. 27. Graber TM. Postmortems in posttreatment adjustment. Am J Orthod. 56. Bjork A. Facial growth in man, studied with the aid of metallic implants. 1966;52:331–352. Acta Odontol Scand. 1955;13:9–34. 28. Bresolin D, Shapiro PA, Shapiro GG, et al. Mouth breathing in allergic 57. Bjork A. Variations in the growth pattern of the human mandible: children: its relationship to dentofacial development. Am J Orthod. longitudinal radiographic study by the implant method. J Dent Res. 1963;42: 1983;83:334–340. 400–411. 29. Mills JRE. A long-term assessment of the mechanical retroclination of 58. Bjork A. A sutural growth of the upper face studied by the implant meth- lower incisors. Angle Orthod. 1967;37:165–174. od. Rep Congr Eur Orthod Soc. 1964:49–65. 30. Welch KN. 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Orthod. 1964;34:1–15. 63. Witzel D. Long-term stability of the mandibular arch following differential 34. Reitan K. Clinical and histologic observations on tooth movement during management of arch length deficiencies, Master’s thesis. Seattle: University and after orthodontic treatment. Am J Orthod. 1967;53:721–745. of Washington; 1978. 35. Englert G. Further determination and implementation of a clinical ideal- 64. Federspiel M. On gnathostatic diagnosis in orthodontics. Int J Orthod. ogy. Angle Orthod. 1960;30:14–25. 1924;10:783. 36. Walters DC. Changes in the form and dimensions of dental arches result- 65. Ochsenbein C, Maynard JG. The problem of attached gingiva in children. ing from orthodontic treatment. Angle Orthod. 1953;23:3–18. ASDC J Dent Child. 1974;41:263–272. 37. Linder-Aronson S. Adenoids: Their effect on mode of breathing and 66. Ballard ML. Asymmetry in tooth size: a factor in the etiology, diagnosis nasal airflow and their relationship to characteristics of the facial skeleton and treatment of malocclusion. Angle Orthod. 1944;14:67–70. and the dentition. A biometric, rhino-manometric and cephalometro- 67. Stoner MM, Lindquist JT, Jack M, et al. A cephalometric evaluation radiographic study on children with and without adenoids. Acta Otolar- of fifty-seven consecutive cases treated by Dr. Charles H. Tweed. Angle yngol Suppl. 1970;265:1–132. Orthod. 1956;26:68–98. 38. Reitan K. Tissue rearrangement during retention of orthodontically 68. Litowitz R. A study of the movements of certain teeth during and follow- rotated teeth. Angle Orthod. 1959;29:105–113. ing orthodontic treatment. Angle Orthod. 1948;18:113–132. 39. Allen RL. A study of the regression phenomenon of orthodontically rotated teeth 69. Mershon JV. The removable lingual arch appliance. 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The effect of extraction of third Am J Orthod Oral Surg. 1958;44:112–140. molars on late lower incisor crowding: a randomized controlled trial. Br 50. Storey E. Tissue response to the movement of bones. Am J Orthod. J Orthod. 1998;25:117–122. 1973;64:229–247. 80. Zawawi KH, Melis M. The role of mandibular third molars on lower 51. Waldron R. Reviewing the problem of retention. Am J Orthod Dentofacial anterior teeth crowding and relapse after orthodontic treatment: a sys- Orthop. 1942;28:770–791. tematic review. Scientific World Journal. 2014;2014:615429. 52. Howes AE. Case analysis and treatment planning based upon the relation- 81. Gallerano R. Mandibular anterior crowding, a postretention study, Master’s ship of tooth material to its supporting bone. Am J Orthod. 1947;33:499–533. thesis. Seattle: University of Washington; 1976. 53. Howes AE. Model analysis for treatment planning: a portion of sympo- 82. Angle EH. Treatment of Malocclusion of the Teeth Angle’s System. 7th ed. sium on case analysis and treatment planning. Am J Orthod Dentofacial Philadelphia: SS White Dental Manufacturing Co.; 1907. Orthop. 1952;38:183–207. 83. Little RM, Wallen TR, Riedel RA. Stability and relapse of mandibular 54. Lude JC. Technique for the determination of the size of the mandibular api- anterior alignment—first premolar extraction cases treated by traditional cal base; its application to growth studies. Angle Orthod. 1967;37:272–284. edgewise orthodontics. Am J Orthod. 1981;80:349–365. CHAPTER 33 Stability, Retention, and Relapse 997

84. Little RM, Riedel RA, Artun J. An evaluation of changes in mandibular 94. Huang L, Artun J. Is the postretention relapse of maxillary and mandibular anterior alignment from 10 to 20 years postretention. Am J Orthod Den- incisor alignment related? Am J Orthod Dentofacial Orthop. 2001;120(1):9–19. tofacial Orthop. 1988;93:423–428. 95. Nett BC, Huang GJ. Long-term posttreatment changes measured by the 85. Manish V, Hughes E. Results of a survey-based study to identify common American Board of Orthodontics objective grading system. Am J Orthod retention practices in the United States. Am J Orthod Dentofacial Orthop. Dentofacial Orthop. 2005;127(4):444–450. 2010;137:170–177. 96. Littlewood SJ, Millett DT, Doubleday B, et al. Retention procedures 86. Riedel RA, Little RM, Bui T. Mandibular incisor extraction–postretention for stabilising tooth position after treatment with orthodontic braces. evaluation of stability and relapse. Angle Orthod. 1992;62:103–116. Cochrane Database Syst Rev. 2006;1. CD002283. 87. Little RM, Riedel RA, Stein A. Mandibular arch length increase during 97. McNeill RW, Joondeph DR. Congenitally absent maxillary lateral incisors: the mixed dentition: postretention evaluation of stability and relapse. Am treatment planning consideration. Angle Orthod. 1973;43:24–29. J Orthod Dentofacial Orthop. 1990;97:393–404. 98. Sproule W. Dentofacial changes produced by extraoral cervical traction to 88. Zachrisson B, JCO/interviews Dr. Bjorn U. Zachrisson on excellence in the maxilla of the Macaca mulatta: a histologic and serial cephalometric finishing. Part 2. J Clin Orthod. 1986;20:536–556. study, Master’s thesis. Seattle: University of Washington; 1968. 89. Johnson Egger N. Long-term stability of maxillary anterior alignment, 99. Magill JM. Changes in the anterior overbite relationship following or- Master’s thesis. Seattle: University of Washington; 1992. thodontic treatment in extraction cases. Am J Orthod Dentofacial Orthop. 90. Little RM, Riedel RA. Postretention evaluation of stability and relapse— 1960;46:755–788. mandibular arches with generalized spacing. Am J Orthod Dentofacial 100. Schudy FF. The control of vertical overbite in clinical orthodontics. Angle Orthop. 1989;95:37–41. Orthod. 1968;38:19–39. 91. McNamara Jr JA, Brudon WL. Orthodontic and Orthopedic Treatment in 101. Douglas J. A serial cephalometric evaluation of the dentofacial changes in the Mixed Dentition. Ann Arbor, MI: Needham Press; 1993. patients treated with Class II intermaxillary forces, Master’s thesis. Seattle: 92. Little RM, Riedel RA, Engst ED. Serial extraction of first premo- University of Washington; 1973. lars—postretention evaluation of stability and relapse. Angle Orthod. 102. Artun J. Caries and periodontal reactions associated with long-term use of 1990;60:255–262. different types of bonded lingual retainers. Am J Orthod. 1984;86:112–118. 93. Dugoni SA, Lee JS, Varela J, Dugoni AA. Early mixed dentition treat- 103. Booth FA, Edelman JM, Proffit WR. Twenty-year follow-up of patients ment: postretention evaluation of stability and relapse. Angle Orthod. with permanently bonded mandibular canine-to-canine retainers. Am 1995;65(5):311–320. J Orthod Dentofacial Orthop. 2008;133:70–76. PART SEVEN Classic Chapters (Online Only) 34

Interceptive Guidance of Occlusion with Emphasis on Diagnosis

Jack G. Dale* and Hali C. Dale

OUTLINE Diagnostic Records, 997.e3 Clinical Analysis, 997.e13 Intraoral, Panoral, or Cone-Beam Computed Dental Development in the Mixed Dentition, 997.e15 Tomography Images, 997.e3 Total Space Analysis, 997.e22 Cephalometric Radiographs, 997.e3 Conventional Method, 997.e22 Facial Photographs, 997.e3 Tweed Method, 997.e23 Study Models, 997.e4 Total Space Analysis, 997.e23 Intraoral Photographs, 997.e4 Timing of Guided Primary Tooth Removal, 997.e27 Diagnosis, 997.e5 Treatment, 997.e28 The Face, 997.e5 Class I Treatment, 997.e30 Proportional Facial Analysis, 997.e5 Treatment Procedures: Interceptive Guidance, The Standard, 997.e7 Active Treatment, 997.e30 Alveolodental Protrusion, 997.e7 Serial Extraction in Class I Treatment, 997.e30 Alveolodental Retrusion, 997.e7 Premolars, 997.e39 Prognathism, 997.e7 Typical Patient for Class I Serial Extraction, 997.e40 Retrognathism, 997.e8 Key Measurements for Diagnosis and The Teeth, 997.e13 Case Evaluation, 997.e45

1,2 “This “Classic Chapter in Orthodontics” is taken from The term serial extraction was first introduced by Kjellgren our fifth edition of Orthodontics: Current Principles and in 1929. Special knowledge is required to carry out this pro- Techniques published by Elsevier in 2012. It is presented as cedure successfully. Unfortunately, Kjellgren’s phrase resulted then written. The chapter contains perspectives and infor- in the indiscriminate removal of teeth by individuals who have mation that remain valuable to orthodontic residents and not appreciated the requisite knowledge. A common miscon- clinicians.” ception is that the procedure is easy because it implies simply the removal of teeth serially. Hotz,3 however, referred to the procedure as guidance of erup- As we learn more about growth and its potentials, more tion. This is a better title than Kjellgren’s because it implies that about the influences of function on the developing den- knowledge of growth and development is necessary to direct the ture, and more about the normal mediodistal position of teeth as they erupt into occlusion. The term guidance of occlu- the denture in its relation to basal jawbones and head sion is even more appropriate because clinicians are interested structures, we will acquire a better understanding of when in the final destination of eruption: the occlusion. One must and how to intervene in the guidance of growth processes have a thorough understanding of growth and development so that Nature may better approximate her growth plan with all its ramifications and must be aware of occlusion of the for the individual patient. In other words, knowledge will dentition, with its relationship to the craniofacial structures and gradually replace harsh mechanics, and in the not-too- function. This chapter discusses the serial extraction of the pri- distant future the vast majority of orthodontic treatment mary teeth to guide the eruption of the permanent teeth into will be carried out during the mixed-dentition period of growth and development and before the difficult age of *An article in memoriam of author Jack G. Dale can be found at adolescence. the following link: http://www.sciencedirect.com/science/article/pii/ —Charles H. Tweed S0889540616001827 997.e1 997.e2 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis a favorable occlusion to intercept, in part, the occurrence of a major malocclusion. When the practitioner is contemplating the correction of an orthodontic problem, the most crucial decision to make is whether teeth should be extracted. Even more demanding is adding the morphogenetic pattern and the dimensions of time, complicating that with the growth and development of the dentition and the craniofacial complex and carrying out the procedure serially.2 Serial extraction is not easy, as so many mistakenly believe. Serial extraction should never be initiated without a comprehensive diagnosis. Teeth may be extracted with the greatest of ease during a so-called serial extraction procedure. However, if the basic principles of diagnosis are ignored, the result will be failure and disappointment. Serial extraction will be inju- FIGURE 34-1 Class II, Division 2, malocclusion with an impacted rious not only to the patient but also to the reputation of the permanent maxillary right canine. During a misguided serial practitioner and ultimately to the profession. Legal concerns extraction program, one mandibular incisor and the maxillary regarding risk management include promiscuous extraction.4 right first premolar were extracted. Unfortunately, since Bunon5 introduced serial extraction to the profession 268 years ago, it has been grossly misunderstood. Lack of understanding and knowledge has produced disastrous results, including a deterioration of the dentition and facial balance. Serial extraction has been criticized and maligned unfairly by individuals who have never used the procedure in practice or acquired the necessary knowledge to perform it well. If serial extraction is based on a thorough diagnosis and carried out carefully and properly on a select group of patients, the procedure can be an excellent and valuable treatment. Serial extraction can reduce appliance treatment time, the cost of treatment, discomfort to the patient, potential iatrogenic sequelae, and time lost by the patient and the parents. To intercept a malocclusion as early as possible and to reduce or, in rare instances, avoid fixed appliance mechanotherapy at the sensitive teenage period is logical. Why allow an unfavorable dental, skeletal, or soft tissue relationship to exist for a number of years if it can be corrected, or significantly improved, early FIGURE 34-2 A 13-year-old girl who did not have the benefit of with a minimum of appliance treatment time? serial extraction and early treatment. Before attempting the treatment of an orthodontic patient using guidance of occlusion, the practitioner must be pre- Early consideration of the corrective measures necessary to pared to meet the challenge of diagnosis. Without question, remedy any type of malocclusion should be a prime concern of the secret of success in orthodontic treatment is a thorough the practitioner. Whatever method is chosen, treatment time understanding of mixed dentition diagnosis. The orthodontist should be at a minimum.6 can have the most comprehensive and sophisticated treatment Patient requests for more technique sensitive lingual, esthetic plan at work in the patient’s mouth; however, if the plan is labial and/or aligner appliances can make serial extraction even implemented in the wrong patient, treatment will fail. This more important. There are increasing concerns of tissue dam- chapter discusses guidance of occlusion with a special empha- age and the iatrogenic potential of our armamentaria and mate- sis on diagnosis based treatment planning. ria technica (see Chapter 30).4 The best way to hide appliances Charles Tweed, whose words are quoted at the beginning of is to not use them or at least to diminish their use. By using this chapter, was a man who devoted more than 40 years of his the benefits of serial extraction in Class I malocclusions, ortho- life to the treatment of the permanent dentition and the devel- dontists can concentrate more fully on the time-consuming opment of precision edgewise mechanotherapy, sometimes and technically demanding Class II and III malocclusions; thus, referred to as “harsh mechanics.” However, during the last 13 these orthodontists increase their usefulness to their profession years of his life, he was vitally interested in treatment during the and to society. mixed dentition period, including preorthodontic guidance, Serial extraction often has been criticized as being a bad pro- guidance of occlusion, and serial extraction. cedure, and it certainly can be more harmful than beneficial if Tweed and many others found that serial extraction, espe- not done properly (Fig. 34-1). The two girls in Figures 34-2 and cially in Class I tooth size–jaw size discrepancy malocclusions, 34-3 are 13 years of age, just at the beginning of adolescence. The improves the alignment of the teeth when they emerge into the girl in Figure 34-2 has a severe Class I tooth size–jaw size discrep- oral cavity. As a result, it creates a better environment “so that ancy. Her treatment required the extraction of four premolar Nature may better approximate her growth plan.” Tweed also teeth and 30 months of mechanotherapy beginning at 13 years. discovered that the interception of dentofacial deformities using The retention period was prolonged because the teeth had been “growth and its potentials” and biologic principles rather than allowed to remain in a crowded irregular relationship for several “harsh mechanics” was an exhilarating and rewarding experience. years. The girl in Figure 34-3 had a similar malocclusion, but CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e3

FIGURE 34-3 A 13-year-old girl who had the benefit of serial extraction and early treatment.

her treatment was completed by 13 years. Serial extraction was begun at 8 years, and the multibonded appliance was inserted at 12 years. The retention period was minimal. Thus, two girls with similar malocclusions were treated differently. Whereas one was just beginning 30 months of treatment at 13 years, the other already was finished and had a more stable result. The recommended routine office procedure performed before FIGURE 34-4 Root resorption of the maxillary central inci- serial extraction requires a complete orthodontic evaluation, sors by impacted canines. (From Dale JG. Trauma: its influ- including a comprehensive patient history and a thorough clini- ence on orthodontic treatment planning. Dent Clin North Am cal and diagnostic record evaluation followed by an appropriate 1982;26:565.) parent or guardian consultation (see Chapters 8-11 and 16). 11. Posttreatment radiographic evaluation allows for appraisal DIAGNOSTIC RECORDS and documentation of the dental health after orthodontic treatment. A complete set of diagnostic records is acquired to develop the diagnosis, including panoral radiographs and cephalometric Cephalometric Radiographs radiographs (or cone-beam computed tomography [CBCT]), Cephalometric radiographs are used for the following: oriented facial photographs, study models, and intraoral photo- 1. Evaluation of craniofaciodental relationships before treat- graphs of the dentition. The objective of taking quality records is ment to secure clinical accuracy for the purpose of establishing a sound 2. Assessment of the soft tissue matrix diagnosis and being able to communicate the therapeutic needs 3. Classification of facial patterns (as in the proportional facial to the parent and patient as well as general or pediatric dentist.7 analysis) (see Figs. 34-8 to 34-17) 4. Calculation of tooth size–jaw size discrepancies (as in the Intraoral, Panoral, or Cone-Beam Computed total space analysis) Tomography Images 5. Determination of mandibular position Dental radiographs must be taken for the following reasons: 6. Prediction of growth and development 1. Protection of the patient and documentation for the ortho- 7. As a basis for monitoring of skeletodental relationships dontist during treatment 2. Detection of congenital absences of teeth 8. Detection of pathologic conditions before and after treatment 3. Detection of supernumerary teeth 9. Assessment of trauma after facial injuries 4. Evaluation of the dental health of the permanent teeth 10. These radiographs and their pretreatment and posttreat- (detection of pathologic conditions in the early stages) ment evaluation allow for long-term improvement in treat- 5. Assessment of trauma to the teeth after an injury ment planning. 6. Detection of evidence of a true hereditary tooth size–jaw size discrepancy such as the resorptive pattern on the mesial Facial Photographs of the roots of the primary canines Figures 34-5 and 34-6 illustrate the requirements of the 7. Determination of dental age of the patient by assessing the American Board of Orthodontics for oriented facial and length of the roots of permanent unerupted teeth and the intraoral photographs.8 Facial patterns play an important amount of resorption of primary teeth, as in dental age role in diagnosis and treatment planning, especially in serial analysis extraction. From a practical standpoint, the photographs 8. Calculation of the total space analysis (see Figs. 34-46 to allow the orthodontist to better identify the patient. The 34-56) prime objective of diagnosis and treatment in relation to the 9. Detection of root resorption before, and by means of com- face should be the creation of harmony and balance: a favor- parison, during and after treatment (Fig. 34-4) able, proportionate relationship between the teeth, skeletal 10. Evaluation of third molars before, during, and after treatment pattern, and soft tissue matrix, including the profile. Similar 997.e4 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

Requirements: Lateral view: • Ears displayed • Full face displayed in natural head position • Left eyelash slightly visible

Frontal views: • Teeth in occlusion • Eyes are open and looking into camera • Ears exposed • Lips relaxed and in contact • No distracting eyewear or jewelry • Cropped to reveal facial symmetry and balance • Inter-pupillary line bisecting the frame revealing top of shoulders and neck • Use the same format for the smiling and nonsmiling photographs FIGURE 34-5 American Board of Orthodontics requirements for facial photographs. (From American Board of Orthodontics. Specific Instructions for Candidates. St. Louis: 2016. www. americanboardortho.com/orthodontic-professionals/about-board-certification/clinical-examination/case-record-preparation/photograph-requirements.) to cephalometric radiographs, facial patterns are invaluable 6. To evaluate functional occlusion, potentially with the aid of for the following: articulators 1. Evaluation and documentation of craniofacial (and dental) 7. As a basis from which to measure progress during treatment relationships and proportions before treatment 8. To detect abnormalities (e.g., localized enlargements and 2. Assessment of soft tissue profile and muscle balance distortion of arch form) 3. Proportional facial analysis and evaluation of symmetry 9. These records and their pretreatment and posttreatment 4. Total space analysis in tandem with occlusal curve analysis evaluation allow for long-term improvement in treatment 5. Monitoring of treatment progress planning. 6. These photographs and their pretreatment and posttreatment evaluation allow for long-term improvement in treat- Intraoral Photographs ment planning. Figure 34-6 illustrates the requirements of the American Board of Orthodontics for intraoral photographs.8 Study Models Intraoral photographs are valuable to evaluate and document Study models provide a three-dimensional record of the den- the immediate soft and hard tissue relationships surrounding tition and are essential for many reasons.8 Although CBCT the teeth. They present a time-stamped record of the visual char- radiographic imaging and occlusal scanning and other imag- acteristics of the gingiva as well as the enamel before placement ing technologies may eventually allow us to replace this record, of any appliances. Intraoral photographs add the dimension of models are used for the following: color to the records, which aids in assessing and recording the 1. To calculate total space analysis health or disease of the teeth and soft tissue structures.4 2. To assess and document the dental anatomy Regarding serial extraction, photographs allow the clinician 3. To assess and document the intercuspation to record the steps in the technique, frequently without making 4. To assess and document arch form study models. This is important for self-evaluation and discus- 5. To assess and document the curve of occlusion (occlusal sion with patients and parents as well as our general and pediat- curve analysis) ric dental colleagues. A picture is truly worth a thousand words, CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e5

•Mid-palatal raphe centered•Fill the frame with the entire mandibular •Frame the entire arch with minimal amount of arch at least through the first molars soft tissue displayed•Labial surface of the central incisors parallel to the bottom of the frame •Midline centered in the frame

•Anteriorly include the contralateral central •Occlusal plane should be horizontal and•Use the same format as for the right incisorshould bisect the photograph lateral intra-oral photograph •Posteriorly include at least the first molars •There should be equal display of the •Occlusal plane should be parallel to the posterior dentition frame FIGURE 34-6 American Board of Orthodontics requirements for intraoral photographs. (From American Board of Orthodontics. Specific Instructions for Candidates. St. Louis: 2016. www. americanboardortho.com/orthodontic-professionals/about-board-certification/clinical-examination/case-record-preparation/photograph-requirements.)

and with the ability to share digital images, we are better able development of the face is essential to the practice of den- to communicate and consult on important treatment decisions. tistry (see Chapter 1). To achieve this understanding, one The ability of a lay parent or guardian to see problems that must have some knowledge of faces. have been identified, visualize changes, and share with family Normal growth is unbalanced and therefore progressive, throughout treatment is a great benefit as well. and, noticeably, alterations in facial form and pattern take place. Differential growth processes not only produce a wide range DIAGNOSIS of topographic facial variations but also constitute the developmental basis for malocclusions and congenital facial abnor- To differentiate, categorize, and treat specifically, successfully, malities. To control and use the complex processes of growth and routinely requires an understanding of the fundamental in clinical procedures, an understanding of various concepts is principles of diagnosis. Several analyses related to the face and essential for dentists. teeth are discussed in this section. These examples of the procedures should be followed if treatment is to be successful and Proportional Facial Analysis serial extraction effective. The proportional facial analysis is basically a classification of facial patterns based on the Steiner analysis,9 the Merrifieldand Tweed The Face cephalometric analyses,10,11 and especially the counterpart analy- The infant face is not simply a miniature of the adult face sis of Enlow and Hans.12 Proportional facial analysis includes an (Fig. 34-7). The linkage of the terms growth and development evaluation of the following relationships (Fig. 34-8, A): indicates that the enlargement of the face involves more than • Anterior cranial base (1, 2) progressive increases in size. Growth is a differential process • Posterior cranial base (2, 3) in which some parts enlarge more or less than others and in • Cranial base angle (1, 2, 3) a multitude of directions. Growth is a gradual maturational • Ramus of the mandible (3, 4) process taking many years and requiring a succession of • Corpus of the mandible (4, 5) changes in regional proportions and relationships of various • Gonial angle (3, 4, 5) parts. Many localized alterations occur that are associated • Nasomaxillary complex (6, 7, 8, 9) with a continuous process of soft and hard tissue remodel- • Maxillary dentition (10, 11) ing. An understanding of the mechanisms of growth and • Mandibular dentition (12, 13) FIGURE 34-7 Changes in facial proportions throughout growth and development from infancy to maturity. To show the regional differences in height, depth, and breadth, the newborn skull has been enlarged to the same size as the adult skull. (From Enlow DH, Dale JG. Childhood facial growth and development. In: Ten Cate AR, ed. Oral Histology: Development, Structure, and Function. 5th ed. St. Louis: Mosby; 1998.)

B C

A FIGURE 34-8 Standard or orthognathic facial pattern. A, The basic units associated with the proportional facial analysis. B and C, The patient. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e7

A FIGURE 34-9 A, Class I maxillary and mandibular alveolodental protrusion. B, Typical patient profile.

The posterior maxillary (PM) plane is possibly the most undertaking, is often extensive and prolonged, and may have to significant plane in the craniofacial complex. The plane be repeated (see Chapter 16). delineates, naturally, the various anatomic counterparts and is a developmental interface between the series of counter- Alveolodental Retrusion parts in front of and behind it. The PM plane thus retains Class I: Maxillary & Mandibular Alveolodental Retrusion. The a number of basic relationships throughout the growth maxillary and mandibular dentitions are back, and the teeth are process. in a Class I relationship (Fig. 34-11). The orthodontist must be particularly careful in treating this type of facial pattern. If The Standard possible, treatment should be done without the extraction of The standard or orthognathic face, as in Figure 34-8, B and C, teeth. This appearance can be seen in individuals who have exhibits a harmonious relationship between the facial struc- had no orthodontic treatment and in patients who have had tures and the cranium, between the maxilla and the mandible, treatment with extractions and without. A dished-in face cannot between the maxilla and the maxillary dentition, between the always be avoided, regardless of the treatment. mandible and the mandibular dentition, between the maxillary Class II: Mandibular Alveolodental Retrusion. The mandibular dentition and the mandibular dentition, and between the soft dentition is back, and the teeth are in a Class II relationship tissue profile and the underlying hard tissue structures (“the (Fig. 34-12). Again, the practitioner must be careful about mesiodistal position of the denture in its relation to the basal extracting teeth in this type of facial pattern. jawbones and head structures”).13 Prognathism Alveolodental Protrusion Class I: Maxillary & Mandibular Prognathism. In maxillary Class I: Maxillary & Mandibular Alveolodental Protrusion. The and mandibular prognathism, both jaws are forward, and the maxillary and the mandibular dentitions are forward, and the teeth are in a Class I relationship (Fig. 34-13). Often this is a most teeth are in a Class I relationship (Fig. 34-9). This facial pattern aesthetic facial pattern. Many motion picture stars exhibit this in general responds well to extraction and, when caution is type of profile. If the teeth are severely crowded, serial extraction exercised, to serial extraction.14,15 should be performed. However, because of the increase in the size Class II: Maxillary Alveolodental Protrusion. The maxillary of the jaws, extractions are not always indicated. dentition is forward, and the teeth are in a Class II relationship, Class II: Maxillary Prognathism. In maxillary prognathism, but everything else is favorable (Fig. 34-10). Routinely, this the maxilla is forward, and the teeth are in a Class II relationship malocclusion can be treated by the extraction of two maxillary (Fig. 34-14). This relationship may be because the maxilla itself first premolars and by serial extraction in the maxilla only. is forward or may result from a long anterior cranial base. Also, Class III. In the interest of brevity and relevance, the Class the cranial base angle may be flat, creating a downward and III category of this analysis is not included in the discussion. forward position of the nasomaxillary complex. This in turn Class III malocclusions are not suitable for serial extraction may rotate the mandible down and back. These are difficult procedures. Mixed dentition Class III treatment is a complicated Class II malocclusions to treat and certainly demand more 997.e8 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

than serial extraction. The malocclusions are complicated skeletal discrepancies that may require not only comprehensive mechanotherapy but also surgical intervention. Midface protrusions, as they are called sometimes, are difficult profiles to correct satisfactorily by orthodontic treatment alone. The nose, at the end of treatment, often is prominent. Retrognathism Class I: Maxillary & Mandibular Retrognathism. In Class I malocclusions exhibiting maxillary and mandibular retrognathism, the maxilla and mandible are back in relation to the other craniofacial structures (Fig. 34-15). It is difficult to produce a favorable profile in these patients because of the lack of horizontal growth and the recessive nature of their profiles. Every effort should be made to encourage a forward development of the jaws. However, this is difficult because the dentition is in a Class I relationship. Over a long time, such a profile can become more recessive and, if serial extraction is being done, the orthodontist could be saddled with the blame. It is important to explain to the parents A during the case presentation that the patient appears to have an unfavorable growth pattern that may get worse regardless of treatment. Class II: Mandibular Retrognathism. In Class II malocclusions exhibiting mandibular retrognathism, the mandible is back. The corpus of the mandible may be small (Fig. 34-16), or the ramus may be narrow. The gonial angle may be proportionately acute. Excessive vertical development may be evident in the nasomaxillary complex (Figs. 34-16 and 34-17), which in turn rotates the mandible down and back, producing a retrognathic mandible and a tendency to open bite. If this is the cause of the retrognathic mandible, the treatment of preference may be surgery or, if less extreme, use of temporary anchorage devices (TADs) to intrude posterior dental segments to allow the forward rotation of the mandible. Regardless, a patient with this facial BC pattern is not a good candidate for serial extraction. McNamara 16 FIGURE 34-10 A, Class II maxillary alveolodental protrusion. B and Brudon found the most common characteristic of Class and C, Typical patient profile and frontal views demonstrating II malocclusions to be a retrognathic mandible, with excessive perioral muscle strain. vertical development.

A FIGURE 34-11 A, Class I maxillary mandibular alveolodental retrusion. B, Typical patient profile. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e9

A FIGURE 34-12 A, Class II mandibular alveolodental retrusion. B, Typical patient profile with adverse lip posture and function supporting the malocclusion during function.

A FIGURE 34-13 A, Class I maxillary and mandibular prognathism. B, Typical patient profile. 997.e10 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

A FIGURE 34-14 A, Class II maxillary prognathism. B, Typical patient profile.

According to the proportional facial analysis, a Class I malocclusion could be associated with a facial pattern characterized by a maxillary and mandibular alveolodental protrusion, maxillary and mandibular alveolodental retrusion, maxillary and mandibular prognathism, maxillary and mandibular retrognathism (even orthognathism), or a combination of these features. What is evident from this analysis is that to treat all Class I malocclusions in the same manner would not be using sound clinical judgment. Class I malocclusions with excessive vertical development of the nasomaxillary area might be treated better by posterior segment impaction with TADS or combined orthodontics and orthognathic surgery or alternate tooth extraction protocols rather than by serial extraction followed by removal of the four first premolars. Similarly, a Class II malocclusion could be a result of maxillary alveolodental protrusion; mandibular alveolodental retrusion; a prognathic maxilla caused by a forward nasomaxillary complex, long anterior cranial base, or flat cranial base angle; a retrognathic mandible caused by a short corpus, narrow ramus, acute gonial angle, and excessive vertical development of the nasomaxillary complex; or a combination of these features. What is even more evident is that one should give serious thought before using serial extraction in Class II malocclusions. Serial extraction aids in the correction of tooth size–jaw size discrepancies but not necessarily in the correction of a Class II relationship. Therefore, the orthodontist must be prepared to place FIGURE 34-15 Class I maxillary and mandibular retrognathism. appliances for an extended time. The diagnosis is particularly important because growth guidance appliances and/or perma- a Class II characteristic). Because the maxilla and the mandible nent teeth other than the four first premolars may be extracted in tend toward retrognathism, the profile that results is in balance. the treatment of these malocclusions, which is referred to later in Similarly, a combination of factors could result in a more the discussion of total space analysis. severe malocclusion. A patient might have a Class I maloc- The proportional facial analysis describes clearly the multi- clusion as a result of excessive vertical development (a Class factorial basis for malocclusion and also explains the way com- II characteristic) and a large gonial angle (a Class III charac- pensation may occur to prevent or minimize a discrepancy. A teristic). However, in this instance, the two factors do not bal- patient’s facial pattern may include a Class I profile with har- ance one another but combine to make the malocclusion more mony and balance that results from a small cranial base angle severe. This Class I dentition would not be a good candidate for (which is a Class III characteristic) and a short corpus (which is premolar extraction or serial extraction. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e11

B C

A FIGURE 34-16 A, Class II mandibular retrognathism with increased vertical facial height. B and C, Typical patient profile and frontal view. Patients with excessive vertical development reveal substantial gingival tissue when smiling albeit philtrum height is within norm.

A FIGURE 34-17 A, Class II mandibular retrognathism. B, Typical patient profile. 997.e12 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

High Angle (Hyperdivergent). The hyperdivergent facial pattern growth, and ectomorphic body type with slow skeletal develop- includes a steep mandibular plane and usually is associated with ment and poor posture. The extraction of teeth is routinely part of a prognathic maxilla; a retrognathic mandible; a maxillary & the orthodontic treatment plan in these facial patterns. Extraction mandibular alveolodental protrusion; an open bite relationship of is necessary to relieve crowding, assist in the correction of the open the incisor teeth; an incompetent lip relationship; a long, sloping bite tendency, and position the mandibular incisors upright. If not forehead with a heavy glabella and supraorbital rims; a nose that too severe, serial extraction may be permissible. is long and thin; and a flattened recessive chin exhibiting muscle Low Angle (Hypodivergent). The low-angle facial pattern tension (Fig. 34-18). routinely exhibits a low MPA accompanied by a favorable Cephalometrically, the mandibular plane to S-N angle is greater horizontal skeletal relationship or an orthognathic facial than 32 degrees in the Steiner analysis. The Frankfurt mandibular pattern, maxillary and mandibular alveolodental retrusion, plane angle (FMA) is greater than 25 degrees in the Tweed analysis. deep overbite relationship of the incisor teeth, prominent chin, Additional features include dolichocephalic head form, leptopro- straight or dished-in soft tissue profile, and a shorter nose sopic facial form, large gonial angle, short ramus, small coronoid (Fig. 34-19). process, antegonial notching, long anterior face height, short pos- Cephalometrically the mandibular plane to S-N is less than terior face height, long lower face height relative to upper face 32 degrees in the Steiner analysis. The FMA is less than 25 height, large cranial base angle (which is responsible for a down- degrees in the Tweed analysis. Additional features include a ward and forward position of the nasomaxillary complex), and a broad brachycephalic head form, a euryprosopic facial form, downward and backward position of the mandible. This pattern in wide-set eyes, prominent cheekbones, a bulbous forehead, turn contributes to a steep occlusal plane (OP) and frequently to less prominent glabella and supraorbital ridges, a small gonial an exaggerated curve of occlusion. The following are characteristic: angle, a broad and long ramus, large coronoid processes, and microgenia, narrow and long symphysis, high and narrow palate, no antegonial notching on the lower border of the mandi- tooth size–jaw size discrepancy caused by large teeth, impacted ble. The anterior face height equals the posterior face height. third molars, small interincisal angle, overerupted incisors despite Compared with the upper face height, the lower face height is an open bite tendency, convex soft tissue profile, weak temporal small. A small cranial base angle is responsible for an upward muscles, restricted pharyngeal space with the tongue forward, and backward position of the nasomaxillary complex and an mouth breathing, narrow nasal apertures, vertical mandibular upward and forward position of the mandible. Macrogenia

FIGURE 34-18 High-angle facial pattern. Facial planes are divergent. Chin profile projection is weak.

FIGURE 34-19 Low-angle facial pattern. Facial planes are convergent. Chin profile projection is strong. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e13

is common. The palatal vault is flat with a wide dental arch 8. Gingival recession on the labial surface of the prominent and potentially small teeth. The mandibular incisors may be mandibular incisor crowded as a result of a deep overbite, or spaced dentition may 9. A prominent bulging in the maxilla or mandible caused by result. More abrasion of teeth occurs along with early forma- the crowding of the canines in the unerupted position tion and eruption of teeth; thin lips; deep mentalis sulcus; 10. A discrepancy in the size of the primary and permanent heavy masseter muscles, with vertical pull; strong temporal teeth, reducing the leeway space muscles; and large pharyngeal space, with a posterior tongue 11. Ectopic eruption of the permanent maxillary first molars, position. Less tongue thrusting occurs when swallowing with resulting in the premature exfoliation of the primary sec- low-angle facial patterns. The nasal apertures are large. The ond molars, which indicates a lack of development in the mandibular growth is horizontal. The body is endomorphic tuberosity area (see Fig. 34-36) with advanced skeletal age and upright posture. These patients have less need for extraction; indeed, every effort is made to avoid the extraction of teeth. Arch length can be gained by correcting the deep overbite and positioning the mandibular teeth upright. Serial extraction, in most instances, is contraindicated. The Teeth According to the Burlington Orthodontic Research Project,17 34% of 3-year-old children enjoy a normal occlusion. By the time they reach 12 years of age, only 11% have a normal intercuspation—a reduction of 23%. Local environmental factors are largely responsible. For example, crowded dentition results from a loss of arch length caused by the premature loss of primary teeth. Serial extraction is an interceptive procedure designed to assist in the correction of hereditary tooth size–jaw size discrepancies. Because the malocclusions of 66% of 3-year-old children FIGURE 34-20 Premature exfoliation of one primary mandibu- are hereditary (with a significant number of tooth size–jaw size lar canine with a resulting midline discrepancy. discrepancies), serial extraction is an invaluable adjunct to interceptive treatment. This is especially true in the case of Class I malocclusions and to a lesser extent in the Class II malocclusions. Class I malocclusions are ideal for serial extraction because the dentition is basically in a favorable relationship and successful treatment is possible with a minimum of mechanotherapy.18,19 The ideal conditions for serial extraction are (1) a true, relatively severe hereditary tooth size–jaw size discrepancy; (2) a mesial step mixed dentition developing into a Class I permanent relationship; (3) a minimal overjet relationship of the incisor teeth; (4) minimal overbite; and (5) a facial pattern that is orthognathic or with a slight alveolodental protrusion. Clinical Analysis Hereditary Crowding. The signs of a true hereditary tooth size–jaw size discrepancy may be outlined as follows: FIGURE 34-21 One permanent mandibular lateral incisor blocked 1. Maxillary and mandibular alveolodental protrusion without lingually with a midline discrepancy. out interproximal spacing 2. Crowded mandibular incisor teeth 3. A midline displacement of the permanent mandibular incisors, resulting in the premature exfoliation of the primary canine on the crowded side (Fig. 34-20) 4. A midline displacement of the permanent mandibular incisors with the lateral incisors on the crowded side blocked out, usually lingually (Fig. 34-21) but occasionally labially 5. A crescent area of external resorption on the mesial aspect of the roots of the primary canines caused by crowded permanent lateral incisors 6. Bilateral primary mandibular canine exfoliation, resulting in an upright positioning of the permanent mandibular incisors; this in turn increases overjet (Fig. 34-22) and/or the overbite as lower incisors retract 7. A splaying out of the permanent maxillary or mandibular incisor teeth caused by the crowded position of the FIGURE 34-22 Bilateral exfoliation of primary mandibular canines unerupted canines (Fig. 34-23) resulting in an increase in overjet, with uprighting of lower incisors. 997.e14 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-23 Splayed maxillary lateral incisors. This is often FIGURE 34-25 Discrepancy in the size of individual teeth. coupled with mesial eruption of the permanent maxillary cus- pids with potential for damage to the lateral incisor roots if appliances are placed.

FIGURE 34-26 Maxillary canine erupted in the premolar position. This may be related to a transposed canine and ectopic premolar or an absent premolar. FIGURE 34-24 Palisading of the maxillary molars. The clinician should monitor for impaction of the second molars with potential need for early third molar removal.

12. A vertical palisading of the permanent maxillary first, second, and third molars in the tuberosity area, again indicating a lack of jaw development (Fig. 34-24) 13. Impaction of the permanent mandibular second molars in the absence of treatment True hereditary tooth size–jaw size discrepancies must be differentiated from crowded dentitions resulting from factors that are more environmental in nature. True hereditary crowding likely will be treated with the aid of extractions and, if discovered early, with serial extraction. However, crowding resulting from environmental factors may be treated without extractions. Environmental Crowding. Environmental crowding may result FIGURE 34-27 Rotated maxillary premolar consuming more under the following conditions: space than it would in its normal position. 1. Trauma that affects surrounding hard and soft tissues 2. Iatrogenic malocclusion caused by ill-conceived space 7. Transposition of teeth (see Fig. 34-38) management 8. Uneven resorption of primary teeth 3. Discrepancy in the size of individual teeth (Fig. 34-25) 9. Rotation of premolar teeth causing loss of space for erupt- 4. Discrepancy between mandibular tooth size and maxillary ing canines (Fig. 34-27) tooth size 10. Ankylosis of primary teeth, most often in first and second 5. Aberration in the shape of teeth (i.e., extra cusps) primary molars, with adjacent tooth tipping 6. Aberration in the eruptive pattern of the permanent teeth 11. Reduction of arch length caused by interproximal caries in (Fig. 34-26) the primary teeth (see Fig. 34-33) CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e15

l1 28 28 Mandible Mandible 26 26

24 l I C 24 M 1 2 1 Pm1 M l l C Millimeters Millimeters 1 1 2 Pm2 Pm1 22 M 22 Pm2 2 M2 20 20 468 10 12 14 468 10 12 14 Years Years FIGURE 34-28 Reduction in arch length as a result of the moving forward of posterior teeth. M1, first molar;I 1, central incisor: I2, lateral incisor; C, canine; Pm1, first premolar;Pm 2, second premolar; M2, second molar. (From Moorrees CF, Reed RB. Changes in dental arch dimension expressed on the basis of tooth eruption as a measure of biologic age. J Dent Res 1965;44:129.)

12. Premature loss of primary teeth resulting in a reduction of 36 arch length from subsequent drifting of permanent teeth 35 (see Figs. 34-34 to 34-37, A) 13. Altered emergence sequence (see Fig. 34-43) 34 Maxillary arch 14. Exfoliation sequence of primary teeth (see Fig. 34-37, A) 33 15. Prolonged retention of primary teeth 32 Because serial extraction is performed during the mixed den- Maxillary arch tition period, careful examination of the transformation from 31 the primary to the permanent dentition is of utmost impor- 30 Depth (mm) tance. A thorough understanding of the eruption sequence and 29 range of timing in tooth eruption is critical. One of the most Mandibular arch important daily aspects in mixed dentition patient evaluation 28 is the observation of the tooth eruption pattern and follow-up 27 Mandibular arch on alterations in the patient’s sequence of eruption. Although 26 there are many permutations on “normal,” intercepting individual, specific developing problems results in reduced needs FIGURE 34-29 Reduction in arch depth. (From DeKock WH. for mechanotherapy. Dental arch depth and width studies longitudinally from 12 years of age to adulthood. Am J Orthod 1972;62:56.) Dental Development in the Mixed Dentition At present, overwhelming scientific evidence indicates that the posterior teeth move forward throughout life. This tends to reduce arch length. Moorrees20 has established that arch length decreases 2 to 3 mm between 10 and 14 years, when the primary molars are being replaced by the permanent premolars (Fig. 34-28). He also has demonstrated that the arch circumference is reduced about 3.5 mm in the mandible of boys and 4.5 mm in girls during the mixed dentition period. DeKock21 measured a 10% decrease in arch length for males and 9% for females over a period of 10 years beyond the period of the mixed dentition, from 12 years to 26 years (Fig. 34-29). Brodie22 has observed that in newborn infants, the tongue tends to fill the oral cavity and often encroaches on the alveolar ridge area. As a consequence of the more rapid anterior growth of the jaws in the postnatal period, the tongue lags behind and comes to occupy a more posterior position in the oral cavity. This is consistent with the upright positioning of the incisors that occurs in many adolescents as noted by Enlow,23 Bjork24 (Fig. 34-30), Tweed,11 and others. These findings suggest that as facial growth continues in an anterior direction into adulthood, it thrusts the mandible into FIGURE 34-30 Upright positioning of incisors with forward the facial musculature, which produces a posterior force vector growth. (From Bjork A. Variations in the growth pattern of the on the crowns of the incisors. Thus, arch length decreases from human mandible: longitudinal radiographic study by the implant the anterior and posterior sides. To repeat, serial extraction is method. J Dent Res 1963;42:400.) 997.e16 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-31 Early mesial shift. Note the use of normal developmental spaces in the mixed dentition to bias the occlusal development for a mesial shift of the mandibular teeth versus the maxillary teeth. (Adapted from Baume LJ. Physiological tooth migration and its significance for the development of occlusion. II. The biogenesis of the accessional dentition. J Dent Res 1950;29:331.)

FIGURE 34-32 Late mesial shift. This pattern is seen when there is minimal developmental spacing in the primary and early mixed dentition. (Adapted from Baume LJ. Physiological tooth migration and its significance for the development of occlusion. II. The biogenesis of the accessional dentition. J Dent Res 1950;29:331.) based on the fact that arch length does not increase. If crowding is evident at 8 years, it will not improve with further growth and development. First Molars. Several situations can exist for the permanent first molars. In patients with a spaced primary dentitionand a straight terminal plane relationship of the primary molars, the permanent mandibular first molars emerge at about 6 years, move the primary molars mesially, close the space distal to the primary canines, convert the straight terminal plane to a mesial step relationship, reduce arch length in the mandibular FIGURE 34-33 Reduction in arch length as a result of caries. dentition, and allow the permanent maxillary molars to emerge into a Class I relationship. This has been referred to as the early to a mesial step, and provides for a Class I relationship of the mesial shift (Fig. 34-31). permanent first molars. This shift has been referred to as the In patients with a closed primary dentition and a straight late mesial shift (Figs. 34-28 and 34-32). If the permanent max- terminal plane, the permanent maxillary and mandibular first illary first molars emerge before the mandibular molars, just the molars emerge into a cusp-to-cusp relationship simply because reverse of the early mesial shift—an abnormal Class II relation- no spaces exist. At about 11 years, the primary mandibular sec- ship—will occur, and a reduction in the maxillary arch length ond molars are exfoliated, and the permanent mandibular first will result. molars migrate mesially into the excess leeway space provided If extensive interproximal caries is allowed to develop by the differences in mesiodistal dimensions of the primary sec- in the maxilla, a similar situation will occur: a reduction of ond molars and the permanent second premolar teeth. Again, arch length causing crowding (Fig. 34-33). If the caries is so this reduces arch length, converts the straight terminal plane extensive that extraction of the primary maxillary second CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e17

FIGURE 34-34 Reduction in arch length as a result of premature loss of primary maxillary second molars.

FIGURE 34-35 Reduction in arch length as a result of premature loss of the primary maxillary first molars. molars is necessary, again, crowding will result (Fig. 34-34). Similarly, and this is contrary to popular belief, premature loss of the primary maxillary first molars will cause crowding (Fig. 34-35). Ectopic eruption of the permanent maxillary first molars, resulting in premature exfoliation of the primary second molars and loss of arch length, indicates a lack of development of the tuberosity. This results in not only crowding but also a Class II molar relationship (Fig. 34-36). FIGURE 34-36 Reduction in arch length as a result of ectopic If the exfoliation sequence of the primary second molars is eruption of the permanent maxillary first molars. reversed and the maxillary molar is lost before the mandibular, a Class II relationship of the permanent first molars will result. to Horowitz and Hixon,26 correlations in size between a single Again, arch length will be reduced, and crowding will occur in primary tooth and its successor range from r = 0.2 to r = 0.6. the maxilla (Fig. 34-37, A). This means that anywhere from 4% to 36% of the successors However, if the primary mandibular second molar is lost far are favorably correlated in size to the primary teeth. In other too early, the mandibular arch length will be reduced to such an words, if the primary tooth is small, its successor will be small. extent that the normal leeway will be exceeded and crowding According to Arita and Iwagaki,27 Hixon and Oldfather,28 Lewis will occur (Fig. 34-37, B). and Lehman,29 Moorrees and Chadha,30 and Jensen et al.,31 The normal leeway, according to Lo and Moyers,25 is 2.6 mm the size correlation between all the primary teeth and their suc- (1.3 mm on each side) in the maxilla and 6.2 mm (3.1 mm on cessors is approximately r = 0.5. Therefore, 25% of the time, a each side) in the mandible. However, this leeway varies consid- positive relationship exists. That is not too favorable for optimal erably and should be measured on each patient. It is possible for occlusion. a discrepancy to exist between the size of the primary teeth and Incisors. Several situations can exist also for the incisors. the size of the permanent teeth to such an extent that no posi- Ideally, the primary spacing of the spaced primary dentition tive leeway is available. A negative leeway may exist. According will be sufficient, together with other factors, to allow for the 997.e18 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis accommodation and favorable alignment of the succedaneous Both of these observations have been substantiated by the permanent incisors (Fig. 34-38). findings of Moorrees20 that show an increase in intercanine In primary dentitions in which there is no interdental spac- width during the period of incisor emergence (Fig. 34-40). ing, the permanent mandibular lateral incisors emerge, and the Moorrees also has demonstrated an increase in arch circum- primary mandibular canines are moved laterally. Thus, a space ference in the maxilla of boys of 1.5 mm and of girls of 0.5 mm is created that enables the permanent maxillary lateral incisors during this period of development.33 to emerge into a favorable alignment. This is referred to as sec- If the primary canines are reduced in size or extracted when ondary spacing and was first described by Baume (Fig. 34-39).32 this natural phenomenon is occurring, an increase in interca- Secondary spacing also occurs when the permanent mandibular nine distance and secondary spacing may not occur. Thus, bor- central incisors are emerging. derline discrepancies may be converted from a nonextraction treatment to extraction. Research conducted by Moorrees and Chadha34 has revealed an increase in the crowding of maxillary and mandibular incisors when they are emerging into the oral cavity. However, 2 mm of crowding in the incisor segment in the mandible of boys will recover to no crowding by 8 years on the average. Girls recover to about 1 mm of crowding. The maxillary dentitions of boys and girls do not exhibit the same tendency to crowding. However, during the eruption of the incisors, 2 to 3 mm of spacing is reduced to 0 (Fig. 34-41). This is a significant finding because it tells the clinician not to be alarmed with a slight amount of crowding in the early stages of emergence of the permanent incisors. The reduction in size, or extraction, of the primary canines should A be deferred. In fact, the patient may not require extraction at all. Intercanine distance increases more in the maxilla and in closed dentitions, which lack primary tooth interdental spaces. A true hereditary tooth size–jaw size discrepancy is characterized by permanent mandibular lateral incisors and a premature exfoliation of the primary canines (Fig. 34-42). Mayne35 described a concept he termed incisor liability. In his discussion, he outlined the way in which incisor liability could be used clinically to determine anterior crowding. He described the following principal variables: 1. The four permanent maxillary incisor teeth are, on the average, 7.6 mm larger than the primary incisors.36 The four permanent mandibular incisors are 6.0 mm larger. This size B differential is the incisor liability. The liability varies greatly FIGURE 34-37 A, Reduction in arch length as a result of prema- from individual to individual, and for this reason, the patient’s ture exfoliation of the primary maxillary second molar. B, Reduc- own tooth measurements should be used in the analysis. A tion in arch length as a result of premature loss of the primary favorable incisor liability exists when the spacing of the maxillary or mandibular second molar.

FIGURE 34-38 Primary spacing. Allows larger incisors to erupt with reduced chance of crowding. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e19

primary anterior teeth is sufficient to allow for the eruption of 5. During the period of permanent incisor eruption, notable the permanent incisors without any crowding (see Fig. 34-38). amounts of intercanine arch width development occur in the 2. A more precarious incisor liability situation exists when no maxillary and mandibular dentition. In the mandible, the primary spacing is present in a closed primary dentition. increase occurs between 6 and 9 years for boys and between Then the individual must rely on the development of sec- 6 and 8 years for girls. In the maxilla, it increases longer, to ondary spacing to create sufficient space for the permanent 16 years in boys and 12 years in girls (see Fig. 34-40). incisors to emerge without crowding (see Fig. 34-39). 6. After 10 years of age, little intercanine arch width change 3. An impossible situation exists when the incisor liability is of is expected in the mandible of boys or girls. The aver- such magnitude that growth and development will never be age increase in the mandibular dentition of boys and able to meet the space demands required by the permanent girls is about 3 mm; in the maxilla, it is about 4.5 mm incisors. Such patients are doomed to severe crowding and (see Fig. 34-40). irregularity from the outset (see Fig. 34-42). 7. The permanent incisor teeth erupt slightly labial to the arch 4. In the primary dentition, the interdental spacing may range position of the primary incisors and for a time at least are between 0 and 10 mm in the maxilla, with an average of 4 more procumbent.35 mm, and between 0 and 6 mm in the mandible, with a range Incisor crowding may be assessed by using the variables just of 3 mm. described. First, a favorable situation, described previously,

FIGURE 34-39 Secondary spacing occurring when the permanent mandibular lateral incisors are emerging.

Millimeters +4 +2 0 −2 −4

FIGURE 34-40 Average intercanine distance. M1, First molar; I1, central incisor; I2, Iateral incisor; C, canine. (From Moorrees CF, Reed RB. Changes in dental arch dimension expressed on the basis of tooth eruption as a measure of biologic age. J Dent Res 1965;44:129.) 997.e20 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-41 Available space in the incisor segment. (From Moorrees CF, Chadha IM. Available space for the incisors during dental development: a growth study based on physiological age. Angle Orthod 1963;33:44.)

TABLE 34-1 Incisor Liability Situation Maxilla (mm) Mandible (mm) Favorable: Primary Spacing Incisor liability −6.2 −4.3 Interdental spacing +4.0 +3.0 Incisor position +2.2 +1.3 — 6.2 4.3 Amount of crowding — —

Precarious: Secondary Spacing Incisor liability −9.2 −7.3 Interdental spacing +4.0 +3.0 Intercanine arch width +3.0 +3.0 Incisor position +2.2 +1.3 — 9.2 7.3 Amount of crowding — —

Impossible: Crowding Exceeds Compensations Incisor −14.2 −12.3 Interdental spacing +4.0 +3.0 Intercanine arch width +3.0 +3.0 Incisor position +2.2 +1.3 — 9.2 7.3 Amount of crowding 5.0 5.0 FIGURE 34-42 Lingual eruption of the permanent mandibular lateral incisors as a symptom of crowding and its effect on sec- spacing so that the permanent incisors erupt without apprecia- ondary spacing. Asterisks in drawing demonstrate inadequate ble crowding (see Fig. 34-39 and Table 34-1). In these patients, arch length for erupting canines. the practitioner avoids interproximal reduction or extraction of primary canines. exists when sufficient primary spacing is present in the spaced Finally, an impossible situation exists with a true heredi- primary dentition to allow for the eruption of the permanent tary tooth size–jaw size discrepancy and an incisor liability that incisors without crowding (Table 34-1; see also Fig. 34-38). cannot be compensated by interdental spacing, an increase in Second, a precarious situation exists with a primary den- intercanine arch width, or labial positioning of the permanent tition with no anterior developmental spaces. A substantial incisors (see Fig. 34-42 and Table 34-1). Serial extraction can be increase in intercanine width is necessary to provide secondary beneficial for these individuals. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e21

FIGURE 34-45 Prolonged retention of the mandibular second deciduous molar, causing crowding of the first premolar.

An unfavorable sequence can produce crowding. For instance, if the second molars erupt early, they may affect the canines in the maxilla and the second premolars in the mandible (Fig. 34-43). Maxillary second molars erupt ahead of mandibular molars in 89.11% of Class II patients, but in only 56.5% do maxillary first molars erupt ahead of their mandibular counterparts.25 There- fore, second molars are more important than first molars in the development of a Class II relationship. Early exfoliation of primary teeth can disrupt the alignment of the dentition, reducing arch length in the maxilla (see Figs. 34-34, 34-35, and 34-37) and mandible (see Fig. 34-37, B). Prolonged retention of primary teeth can cause crowding of the permanent teeth in the maxilla (Fig. 34-44) or mandible (Fig. 34-45). FIGURE 34-43 Unfavorable emergence sequence. The perma- Clinically, the primary second molars appear to resist mesial nent second molars are emerging early, blocking the space for migration to some extent. Rarely does the orthodontist observe maxillary canines and mandibular second premolars. primary mandibular second molars tipped mesially after the premature loss of primary first molars. However, the permanent mandibular first molars are observed to have an exaggerated mesial inclination after the premature loss of the primary second molars. The relative position of the unerupted premolars is crucial in this situation. When the primary mandibular second molars are lost prematurely, the permanent second premolars are often deep in the alveolar bone. This may encourage the permanent first molar to tip forward. When the primary mandibular first molar is lost prematurely, the permanent first premolar (which is scheduled to emerge before the second premolar) is not so deeply embedded in bone. Therefore, the tendency for tipping of the primary second molar is not as great. The unerupted first premolar tends to support the primary second molar. Contrary to popular belief, arch length can be reduced, and space can be lost after premature exfoliation or extraction of the primary first molar (see Fig. 34-35). This is especially true in the FIGURE 34-44 Prolonged retention of the primary maxillary mandible, where the formation of a knife-edge ridge of alveo- second molar causing crowding of the permanent canine. lar bone obstructs and retards the emergence of the underlying first premolar. Canines, Premolars, and Second Molars. The most frequently The premature loss of primary molars immediately leads one occurring sequence of eruption in the maxilla is as follows: to consider space maintenance. However, the use of space main- permanent first molar, central incisor, lateral incisor, first tainers depends on a thorough diagnosis and may be modified premolar, second premolar, canine, second molar. The most with subsequent treatment planning. If the patient has a normal frequently occurring sequence in the mandible is permanent dentition or the treatment plan does not include the extraction first molar, central incisor, lateral incisor, canine, first premolar, of permanent teeth, a space maintainer may be placed. Indeed, second premolar, second molar. According to Lo and Moyers,25 in the borderline situation, maintenance of the “E” space may this combination produces the highest incidence of favorable be all that is indicated to maintain a nonextraction treatment occlusion. More girls than boys have a favorable combination. approach (See also Chapter 16). 997.e22 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

In the maxilla, about 90% of the time, the first premo- Garcia-Hernandez and Dale40 completed a study of 60 lar emerges ahead of the canine. This is favorable for serial Class I mixed dentition patients in the authors’ practice. extraction and maintenance of the overbite because the One objective was to compare the conventional method, the maxillary incisors are not held forward. About 10% of the Tweed method, and the total space analysis method in the time, the sequence is unfavorable for serial extraction and diagnosis of tooth size–jaw size discrepancies before serial the overbite. extraction. Sixty individuals (30 boys and 30 girls) with a In the mandible, about 80% of the time, the canine mean chronologic age of 8 years, 4 months (range, 7 years emerges ahead of the first premolar.25 This eruption sequence 7, months to 11 years, 3 months) were selected from the decreases overbite because it maintains the mandibular inci- records of the practice. sors in a forward position.37 However, the sequence is not favorable for serial extraction. About 20% of the time, the Conventional Method sequence is favorable for serial extraction but not for main- The “conventional” calculations were done as follows. For tenance of the overbite; that is, the first premolars are ahead space required, the four mandibular incisors were measured at of the canines. their greatest mesiodistal crown diameter by means of a sliding Serial extraction is beneficial to prevent resorption of the Boley gauge with pointed beaks. All measurements were made roots of the maxillary lateral incisors by impacted canines. with the gauge parallel to the incisal edges of the teeth, and all When the primary canine is extracted in serial extraction, the readings were to the nearest 0.1 mm (Fig. 34-46). The values for space between the lateral incisor and the primary first molar is unerupted canines and premolars were obtained by measuring reduced substantially. However, when the primary first molar their greatest mesiodistal crown diameter or their images on the is extracted at the proper time, the first premolar erupts, allow- periapical radiograph (Fig. 34-47). ing the unerupted permanent canine to move away from the root of the lateral incisor. On extraction of the first premolar, the canine then erupts into place without difficulty and without danger to the lateral incisor. Certain conditions exist, which will be discussed later, under which primary first molars are extracted before the primary canines to allow the premolars to erupt. This extraction may even be done, in the presence of concern, in nonextraction malocclusions. To their knowledge, the authors have not had a lateral incisor root resorbed by an impacted canine in 33 years of practice using serial extraction procedures. Total Space Analysis The mixed dentition analyses historically were dentally oriented. Unfortunately, even today, tooth size–jaw size discrepancies diagnosed in the mixed dentition period still are evaluated by dental-oriented analyses. These analyses will be referred to as conventional methods. Their aim is to evalu- FIGURE 34-46 Measurement of space required on study modate, as accurately as possible, future crowding in the perma- els with a Boley gauge. Digital models allow this to be done nent dentition using a prediction of the mesiodistal width efficiently with a variety of space analyses and size discrepancy of the permanent mandibular canines and premolars. The evaluations. value obtained is added to the already known measurement of the permanent mandibular incisors. This represents space required. The space required is subtracted from the arch circumference of space available. If the result is significantly negative, future crowding can be predicted. Tweed,38 studying the relationship between the mandibular incisors and the mandibular plane, found that if the teeth are not in a stable relationship with the basal bone after treatment, the result may relapse. In view of this, the dental-oriented mixed dentition analysis alone is not adequate. A facial-oriented analysis, incorporating the relations of the incisor teeth to the basal bone, is preferable. This analysis will be described as the Tweed method. Furthermore, the various mixed dentition analyses demonstrate the discrepancy only and do not indicate the exact area where the discrepancy occurs. In many instances, the problem is confined to one specific area. Because one can direct treatment specifically to one area, knowledge of the area affected is desirable. The total space analysis provides this precise FIGURE 34-47 Measurement of space required on the periapi- information.39 cal radiograph with a Boley gauge. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e23

To reduce the radiographic enlargement, the formula recom- The difference in the values obtained for space required and mended by Huckaba41 was used in all radiographic measurements: space available was the amount of the discrepancy. X = y x1 y1 Tweed Method The values for space required and space available were obtained where X is the estimated size of the permanent tooth, x1 is the as required for the conventional method (see Figs. 34-46 to radiographic size of the permanent teeth, y is the size of the pri- 34-49). An assessment of the relations between the axial incli- mary mandibular second molar on the cast (Fig. 34-48), and y1 nation of the mandibular incisors and the basal bone was made is the radiographic size of the primary molar. on a tracing of the lateral cephalogram. The amount of alveo- The values obtained for the mandibular incisors on the cast lodental protrusion or retrusion was assessed and incorporated and those for the canines and premolars on the radiograph were into the mixed dentition analysis (Fig. 34-50). added to provide the space required. Tweed Foundation research has established the following The space available was obtained by extending a brass relationships: wire from the mesiobuccal of the first permanent molar on • When the FMA is between 21 and 29 degrees, the Frankfort one side to the mesiobuccal of the molar on the opposite mandibular incisor axis angle (FMIA) should be 68 degrees. side, passing through the buccal cusps and incisal edges of • When the FMA is 30 degrees or greater, the FMIA should be the remaining teeth (Fig. 34-49). The wire was straightened 65 degrees. carefully and measured with a pointed Boley gauge to the • When the FMA is 20 degrees or less, the incisor mandibular nearest 0.1 mm. plane angle (IMPA) should not exceed 92 degrees. If for a specific FMA (30 degrees) the FMIA (49 degrees) did not correspond, an objective line was traced to form the required FMIA (65 degrees). Then the distance between this objective line and the line that passed through the actual axial inclination of the mandibular incisors was measured on the OP with pointed calipers to the nearest 0.1 mm (6 mm). This figure was multiplied by 2 to include right and left sides (12 mm). The total was the cephalometric correction, which then was added to the difference between space required in space available to yield the total discrepancy (see Fig. 34-50). Total Space Analysis This method was divided into three areas—anterior, middle, and posterior—and the resulting values for each area were added together to yield the final deficit. Anterior Area. For the anterior area, the calculation of the difference between space required and space available was done as before. However, the space required included, in addition to tooth measurement and cephalometric correction, soft tissue FIGURE 34-48 Measurement of the primary second molar on modification. the study model with a Boley gauge to aid in assessing a radio- Tooth Measurement. Measurements of mandibular incisor graphic enlargement. widths on the cast were added to the values obtained from the radiographic measurements of the canines. Both measurements were made according to a previously described technique (see Figs. 34-46 to 34-48). Cephalometric Correction. The cephalometric correction was calculated as for the Tweed method. However, instead of measurements being made of the distance (in millimeters) on the OP between the objective line and the line indicating the true axial inclination of the mandibular incisors, the actual FMIA (in degrees) was subtracted from the proposed angle, and the difference (in degrees) was multiplied by a constant (0.8) to give the difference in millimeters (Fig. 34-51). Soft Tissue Modification. Whereas the Tweed method added the anterior skeletal dental (hard tissue cephalometrics) relationships to the dental-oriented mixed dentition analysis, this method also adds a consideration of the soft tissue profile. Thus, the teeth, jaws, and soft tissue are involved in the assessment. The soft tissue modification was derived by measuring the FIGURE 34-49 Measurement of space available on the study Z angle of Merrifield10,39 and adding the cephalometric correc- model with a brass ligature wire. Digital model analysis makes tion (in degrees) to it. If the corrected Z angle was greater than this manual measurement step unnecessary. 80 degrees, the mandibular incisor inclination was modified 997.e24 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-50 Tweed method. Cephalometric (ceph.) correction to factor dental protrusion into space analysis. In this patient, according to Tweed goals, the lower incisal edge is 6 mm ahead of where it should be. If the incisor is to be uprighted to the Tweed goal, 6 mm per side of space (12 mm total) are required.

FIGURE 34-51 Total space analysis. Anterior arch cephalometric correction. For patient ML, using FMIA actual minus goal provides an 18 degree difference. Multiplied by .8 would indicate 14.4 mm of needed arch length to achieve the Tweed goal for lower incisor angulation. as necessary (up to an IMPA of about 92 degrees). If the cor- If lip thickness was greater than chin thickness, the difference rected angle was less than 75 degrees, additional upright posi- (in millimeters) was determined, multiplied by 2, and added to tioning of the mandibular incisors was necessary. Upper lip the space required. If it was less than or equal to chin thickness, thickness was measured from the vermilion border of the lip no soft tissue modification was necessary. to the greatest curvature of the labial surface of the central Figure 34-52 portrays patient M.L., described in Figure incisor. Total chin thickness was measured from the soft tissue 34-51, who had a typical Class I malocclusion with an alveo- chin to the N-B line. lodental protrusion and an incompetent lip relationship (see CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e25

A B

C D

E F FIGURE 34-52 Patient M.L. A and C, Before treatment. B and D, After treatment. E and F, Bal- ance and harmony persist as an adult 15 years after orthodontic treatment. 997.e26 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-53 Total space analysis. Measurement of space FIGURE 34-55 Total space analysis. Measurement of space available in the anterior area. available in the middle area.

the mesiobuccal of the opposite molar (Fig. 34-53). The wire then was straightened and measured with a pointed caliper to the nearest 0.1 mm. This value was subtracted from the total B space required to yield the deficit. Middle Area. For the middle area, calculations were made of the difference between space required and space available. In this instance, however, the mandibular curve of occlusion was considered. Tooth Measurement. The crown widths of the permanent mandibular first molars were measured at their greatest A mesiodistal diameter on the cast. These values were added to the measurements of the premolars obtained from the radiographs (see Figs. 34-46 to 34-48). Curve of Occlusion. The following describes the procedures for the calculations for the curve of occlusion. The space required to level the mandibular curve of occlusion was determined (Fig. 34-54). A flat object was placed on the occlusal surfaces of the mandibular teeth, contacting the permanent first molars and the incisors. The deepest point between this flat surface and the occlusal surfaces of the primary molars was measured on both sides. The curve of occlu- B sion formula was applied, and the space required for leveling was determined. This was added to the tooth measurements to complete the space required. The curve of occlusion formula used the greatest depth of each side:

(Right side depth + Left side depth)/2 + 0.5 mm

The space available was determined by placing two brass wires from the mesiobuccal of the primary first molars to the A distobuccal of the permanent first molars Fig.( 34-55). These were measured as before, added together, and subtracted from the space required. Posterior Area. For the posterior area, the space required FIGURE 34-54 Total space analysis. A, curve of occlusion; B, and space available were determined (including that presently leveled curve of occlusion increasing length. available and that predicted). The space required consisted of the sum of the mesiodistal widths of the two second and third Fig. 34-52, A). Note the improvement in muscle balance and molars, which were unerupted in these patients (Fig. 34-56). facial harmony after serial extraction and active treatment (see Because they were unerupted, radiographic enlargements Fig. 34-52, B). had to be calculated. However, the formula used for the The space available was obtained by placing a brass wire conventional method was modified. In this instance, the from the mesiobuccal of the primary first mandibular molar to permanent mandibular first molars were substituted for the CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e27

* Available * Predicted

10 11 21

A B FIGURE 34-56 Total space analysis. Measurement of the (A) available and (B) predicted space in the posterior area.

primary second molars. A second complication was that often TABLE 34-2 Mixed-Dentition Analysis: the third molars were not visible on the radiographs. In this Comparison of the Conventional and case, Wheeler’s measurements were used, and the calculation Tweed Methods in a Sample Patient was as follows: Conventional Tweed Method X y x1/y1 = − Sample Patient Method (mm) (mm) where X is the estimated value of the permanent mandibular Space required −69.3 −69.3 third molar in the individual patient, x1 is Wheeler’s values for Space available +69.1 +69.1 third molars, y is the actual size of permanent mandibular first Discrepancy −0.2 −0.2 molar on the cast, and y1 is Wheeler’s value for first molars. Cephalometric — −8.0 The space available consisted of the space presently avail- Correction able plus the estimated increase or prediction. The estimated Total discrepancy −0.2 −8.2 increase was 3 mm per year (1.5 mm for each side) until 14 Difference between — −8.0 years in girls and 16 years in boys. Therefore, the age of the two methods patient was subtracted by 14 or 16. The result was multiplied by 3 to obtain the estimated increase for the individual patient. The space presently available was obtained by measuring the Patient M.R. (see Figs. 34-85 and 34-87) also is a good exam- distance on the OP between a perpendicular line drawn from ple of a favorable serial extraction situation: a Class I mixed the OP tangent to the distal surface of the permanent first molar dentition malocclusion with an anterior discrepancy in the to the anterior border of the ramus on the lateral cephalometric form of a moderate alveolodental protrusion and a posterior tracing (see Fig. 34-56). After the presently available space and discrepancy with a high-angle facial pattern. The same teeth the predicted space were totaled to give the space available, the were extracted as in patient M.L. for different reasons. The ante- space required was subtracted. rior discrepancy is more related to the alveolodental protrusion Discussion. Because the total space analysis involves the in patient M.L. than in patient M.R. The posterior discrepancy permanent molars, it was not possible to compare its results is more related to the high-angle facial pattern in patient M.R. with those of the other two procedures. However, when than in patient M.L. Thus, each individual is treated differently the results of the conventional method are compared with depending on the results of the various diagnostic procedures, those of the Tweed method, the differences become highly including total space analysis. Total analysis may thus result in significant. extraction of varied teeth or nonextraction, with mechanother- The assessment of axial inclination of the mandibu- apy varying to match the correction of individual discrepancies lar anterior teeth with respect to the basal bone must be from a balanced dentofacial form. included in the analysis of mixed dentition malocclusion so that there will be harmony in the facial profile and stability Timing of Guided Primary Tooth Removal in the dentition. The cephalometric correction in the Tweed Three factors may be applied by the clinician in deciding method accounts for 9.8% of the space required, a consider- the optimal time for the removal of teeth in the guidance of able amount. occlusion: Table 34-2 illustrates the differences between the conven- 1. The effect of extraction of the primary tooth on the eruption tional method and the Tweed method in one of the subjects of of its permanent successor the investigation. Comparison of the techniques makes it evi- 2. The amount of root formation at the time of emergence dent that completely different treatment plans will result. 3. The length of time for the attainment of various stages of Patient M.L. (see Figs. 34-51 and 34-52) exemplifies an ideal root development serial extraction situation: a Class I mixed dentition malocclu- Serial extraction, if carried out too early in the primary sion with an anterior discrepancy in the form of an alveoloden- dentition, can delay the eruption of permanent successors. In tal protrusion and a posterior discrepancy with a medium angle the case of early extraction of the primary molar, Fanning42 facial pattern. The first premolars were extracted to correct the reported an initial spurt in eruption of the premolar. This lev- anterior discrepancy, and the third molars were extracted to eled off and the tooth then remained stationary, erupting later correct the posterior discrepancy. than its antimere with a normally shedding primary precursor. 997.e28 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

Girls Boys

Maxilla

Mandible

Girls Boys

FIGURE 34-57 Assessment of dental age by means of tooth emergence (±1 standard deviation). This is a classic study taken from records of 93,000 children and demonstrates individual tooth variability and sex-linked timing of eruption. (From Hurme VO. Ranges in normalcy in eruption of permanent teeth. J Dent Child 1949;16:11.)

If serial extraction is initiated with the extraction of the pri- and the emergence of permanent teeth (Fig. 34-57), together with mary canines, the length of the roots of the premolars is not root resorption of the primary teeth and the factors that influence an important consideration. If, however, the orthodontist is these processes, is mandatory in the timing of serial extraction. contemplating initiating serial extraction by removing the primary first molars, the length of the root of the premolar is an TREATMENT important consideration and guide for the commencement of the procedure.43 The authors adhere to the principles and objectives of the The relative eruptive rates of the permanent canines and first Tweed philosophy. Clinically, Tweed advocated maximal facial premolars influence the decision about which primary teeth harmony and balance. To achieve this goal, he recognized that should be extracted. If, for example, during an examination of mandibular incisor teeth must be placed upright over basal the radiographs, the orthodontist observes the permanent man- bone. The primary objective in treatment is to obtain maximal dibular first premolar crown ahead of the permanent canine health, aesthetics, function, and stability. Specifically, it is excel- crown, the premolar with less than one half its root formed, and lence in tooth alignment, arch form, and axial inclination of the the mandibular incisors crowded, the primary canine should teeth, with optimal occlusal intercuspation of the maxillary and be extracted to relieve the crowding. The primary first molar mandibular dentitions. should be left until the first premolar has attained one half its Objectives of treatment include the following: root length. If, on examining the radiographs, the orthodon- 1. Decrease in the FMA, indicating a favorable rotation of the tist observes the premolar crown even with the canine crown, mandible. the premolar with one half its root formed, and an alveoloden- 2. Decrease in the IMPA, indicating the reduction of the alveo- tal protrusion, the primary first molar should be extracted to lodental protrusion. encourage the emergence of its successor. 3. Increase in the FMIA, also indicating an upright positioning Dental age, assessed particularly by root length, is an essential of the mandibular incisor teeth. requirement in the decision of a serial extraction program and in 4. Decrease in the OP angle throughout treatment, indicating the initiation of interceptive and definitive fixed appliance treat- that one is not extruding the posterior teeth or dumping the ment. A knowledge of root development, relative eruptive rates, anterior teeth forward. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e29

AB FIGURE 34-58 A, Posterior limits of the nasomaxillary area: a line perpendicular to the line of sight passing through the junction of the anterior and middle cranial fossae. B, Anterior limit of the nasomaxillary complex: a line extending from the internal surface of the frontal bone and running perpendicular to the ethmoid. (Adapted from Enlow DH, Hans MG. Essentials of Facial Growth. 2nd ed, Ann Arbor, MI: Needham Press; 2008.)

5. Decrease in the ANB (A point–nasion–B point) angle, indi- balance. This alone will reduce mechanotherapy by 6 months cating a correction of the skeletal discrepancy. and contribute to the stability of the treatment result. In many of 6. Increase in Merrifield’s Z angle, indicating improvement in these patients, the need for retention is minimal. However, the facial harmony and balance. orthodontist must remember that under ideal serial extraction 7. No lateral, anterior, or posterior expansion of the denti- conditions, the orthodontist is not dealing with severe skeletal tion. This is substantiated by the scientific investigations of discrepancies or severe overjet and overbite problems. The need Enlow,23 who describes specificallythe boundaries of the for long-term retention is greater when skeletal discrepancies nasomaxillary complex (Fig. 34-58). have complicated the orthodontic treatment. Many orthodontists have found from bitter experience that One may ask, “If the roots of the permanent incisor teeth they cannot extend arch length posteriorly, anteriorly, or later- complete their formation in a more favorable position, is their ally unless the position of the teeth results from environmental stability enhanced?” It seems logical that if a tooth completes its factors such as premature loss of the primary teeth. Most of the formation in a site where it will remain when treatment is com- problems during treatment and retention have been associated pleted, it will be more stable. Conversely, if a tooth is left in a with creating space and maintaining alignment where teeth crowded, tipped, and rotated position for several years and then have not been extracted.44 Teeth that have not been placed in moved to a new position relatively rapidly, it will be less stable the correct position relative to the skeletal pattern and soft tis- for a time and will require a longer retention period. sue matrix are more likely to change after fixed appliances have One also may ask, “Does the initiation of serial extraction been removed. The ideal conditions for stability are achieved with the removal of primary teeth always mean that the perma- when teeth are placed in a harmonious relationship early. Long- nent teeth will be removed?” After it has been initiated, serial term use of mandibular fixed retainers may be needed to reduce extraction more often than not will culminate in the extraction age-related maturational changes in the lower anterior segment. of four premolar teeth because arch length, which is deficient to These should be maintained in patients for a prolonged time to begin with, is reduced even more. Despite a thorough diagnosis, preserve the incisor alignment when the mandible grows hori- the treatment plan occasionally needs to be changed to nonex- zontally (see Chapters 1 and 33). traction treatment. The practitioner should always be prepared to Serial extraction allows teeth to become aligned when they treat without extraction if it appears that this can be done success- emerge into the oral cavity rather than to remain in a crowded fully with stability. At the beginning of treatment, the parents unfavorable condition for several years. In the case of alve- should be informed that extractions may be necessary to pro- olodental protrusion, the procedure allows the mandibular duce a successful and stable treatment result. Later, they will be incisors to be positioned upright lingually into a position of relieved and happy if extractions are not necessary. 997.e30 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

An important objective in using the serial extraction tech- CLASS I TREATMENT nique is to make treatment easier and mechanotherapy less complicated, less expensive, and shorter (especially during the Serial extraction has been classically characterized by the teenage years). Treatment can be divided into four categories: removal of the primary canines, primary first molars, and 1. A period of interceptive guidance, extending about 5 years permanent first premolars. With scientific investigation and from age 7.5 to 12.5 years. This consists entirely of the guid- clinical experience, serial extraction has become increasingly ance of occlusion, including serial extraction or space main- sophisticated and precise. Results will be more rewarding if the tenance (or both) and is the most ideal service that can be orthodontist does not cling to a particular sequence but varies it provided. Unfortunately, production of excellent occlusion according to the diagnosis and therapeutic goals. The sequence with serial extraction, or space maintenance alone (or both) that the orthodontist believes is indicated for each patient is possible in only a few patients. When guidance without should be selected.45 further appliances is accomplished, it is most rewarding and satisfying because the results are achieved without mechano Treatment Procedures: Interceptive Guidance, therapy. Active Treatment 2. An initial period of interceptive guidance, extending about Serial Extraction in Class I Treatment 4 years from age 7.5 to 11.5 years, plus a second period of Group A: Anterior Discrepancy—Crowding. This is a typical fixed appliance treatment extending about 1 year from 11.5 serial extraction problem: severe crowding, a developing Class to 12.5 years). Class I and specific types of dental Class II I malocclusion, a favorable overjet–overbite relation of the malocclusions fall into this category. incisor teeth, and an ideal orthognathic facial pattern (Fig. 3. An initial period of interceptive treatment, extending about 34-59). Examination of the radiographs often reveals a crescent 1 year from 8.5 to 9.5 years, plus a period of interceptive pattern of resorption on the mesial of the primary canine roots guidance extending about 2 years from 9.5 to 11.5 years and (see Fig. 34-6). This is an indication of a true hereditary tooth a second period of mechanotherapy extending about 1.5 size–jaw size discrepancy. Radiographic evaluation indicates years from 11.5 to 13 years. Class II malocclusions fall pri- that the first premolars are emerging favorably, ahead of the marily into this category. permanent canines. None of the unerupted permanent teeth 4. A period of fixed appliance treatment, extending for 1.5 to have reached one half root length. Because of this, the primary 3 years from age 11.5 to 14.5 years. Serial extraction is not first molars would not be extracted. The primary canines should involved in this treatment. Wherever possible, the ortho- be extracted to relieve the incisor crowding. dontist should try to avoid extensive treatment in the teenage period because of potential adverse sociopsychological Step 1: Extraction of the primary canines concerns that influence patient cooperation. Step 2: Extraction of the primary first molars. The incisor Of course, these are general classifications. They may vary crowding has improved, the overbite has increased, and considerably depending on the individual patient, the maloc- the extraction site is reduced in size (Fig. 34-60). The clusion, and the dental age. radiographs reveal that the first premolars have reached one half root length. Now is the time to extract the pri-

FIGURE 34-59 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e31

mary first molars to encourage the eruption of the first of the canines, a mesioaxial inclination of the second premolars, premolar teeth. a Class I molar relationship, an improved alignment of the inci- Step 3: Extraction of the first premolars. These teeth are emerg- sors, and residual spaces at the extraction sites (Fig. 34-62). ing into the oral cavity (Fig. 34-61). Because the permanent Step 5: Retention. When mechanotherapy is completed, an ideal canines have developed beyond one half root length, indi- occlusion should be observed, with minimal overjet–over- cating that they are prepared to accelerate their eruption, the bite relationship of the anterior teeth, parallel canine and orthodontist extracts the premolars. premolar roots, ideal arch form, and no spaces (Fig. 34-63). Step 4: Fixed appliance treatment. This is the typical result of serial In addition, the dentition should be aligned in harmony with extraction, a relatively deep overbite with a distoaxial inclination the craniofacial skeleton and soft tissue matrix.

FIGURE 34-60

FIGURE 34-61 997.e32 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

Step 6: Post retention. Again, an ideal occlusion with sta- alignment of the incisors when the primary molars are bility should be evident (Fig. 34-64). Initiating the serial extracted first. Again, the decision is based on the relative extraction procedure with elimination of the primary man- position and length of the roots of the first premolars and dibular canines tends to deepen the overbite. The primary canines. Figure 34-64 illustrates the occlusion 18 years after first molars should be extracted when the underlying first treatment. premolars have reached one half their root length. If this Group B: Anterior Discrepancy—Alveolodental Protrusion. is done, risk of collapse will be minimal. If the mandib- A minor irregularity of the incisor teeth exists. Instead of ular incisors are crowded, the primary canines should be crowding, the patient has an alveolodental protrusion (Fig. extracted first, in preference to the primary first molars. 34-65). The crowns of the first premolars and canines are The orthodontist rarely will be satisfied with the improved at the same level. However, the canines are beyond one

FIGURE 34-62

FIGURE 34-63

FIGURE 34-64 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e33 half root length and are erupting faster than the premolars. canines. Timing is most important to prevent the formation Because the first premolars have one half their root length of a knife-edge ridge. developed, the primary first molars should be extracted to accelerate eruption of the first premolars. This will ensure Step 1: Extraction of the primary first molars that the premolars emerge into the oral cavity ahead of the Step 2: Extraction of the primary canines and first premolars. When the first premolars have emerged sufficiently, they are extracted along with whatever primary canines remain (Fig. 34-66). No effort is made to prevent lingual tipping of the incisor teeth because the objective is to reduce the alveolodental protrusion. Step 3: Fixed appliance treatment. Note how beautifully the dentition is aligning itself (Fig. 34-67). Little mechanical treatment will be required. Step 4: Retention. Retention in the mandible is less crucial because minimal irregularity was present before treatment (Fig. 34-68). Group C: Middle Discrepancy—Impacted Canines. The tooth size–jaw size discrepancy is severe, causing premature exfoliation of the primary canines (Fig. 34-69). Note the splaying of the incisors because of crowding in the apical area. Often parents interpret this spacing as evidence for nonextraction treatment. The orthodontist must explain that this is a sign of severe crowding. The radiograph will reveal that the first premolars are ahead of the canines in eruption and have attained one half their FIGURE 34-65

FIGURE 34-66

FIGURE 34-67 997.e34 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-68

FIGURE 34-69 root length. Treatment begins with the extraction of the primary with fixed appliances for fear of causing the incisor roots to first molars (remember, here primary canines have been lost). resorb as lateral incisor roots move distally. The impacted permanent maxillary canines may cause severe splaying of the maxillary incisors to such an extent Step 1: Extraction of the primary first molars that the lateral incisors do not contact the primary canines Step 2: Extraction of the first premolars. For reasons explained (see Fig. 34-69, bottom right). In this situation, extract- in group A, step 3, the first premolars are now due for ing the primary canines first does little good. Better advice extraction (Fig. 34-70). is to extract the primary first molars to encourage the first Step 3: Fixed appliance treatment. Note the typical result of premolars to emerge as early as possible. The canines then serial extraction (Fig. 34-71). will have space to migrate away from the apices of the inci- Step 4: Retention. Again, note the desired result of mechano sors and begin their eruption into the oral cavity. In this therapy (Fig. 34-72). instance, the practitioner should be concerned more with Group D: Enucleation in the Mandible. If it is evident that correcting canine crowding than with incisor irregularity. the canines will emerge into the oral cavity ahead of the first Every effort should be made to avoid correcting the incisors premolars, the primary first molars can be extracted and the first CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e35

FIGURE 34-70

FIGURE 34-71

FIGURE 34-72 997.e36 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-73 premolars may be enucleated (Fig. 34-73). This will encourage distal migration of the canines as they erupt.

Step 1: Extraction of the primary first molars and enucleationof the mandibular first premolars Step 2: Extraction of the primary maxillary canines and maxillary first premolars. In the maxilla, the first premolars usually emerge before the canines (Fig. 34-74). Therefore, enucleation is less likely to be indicated. At this point, the mandibular canines can be observed emerging favorably into the oral cavity. Step 3: Mechanotherapy (Fig. 34-75). The patient is now ready for the fixed appliance multibracket appliance treatment. Step 4: Retention Group E: Enucleation in the Maxilla and Mandible. On occasion, the canines in the maxilla and mandible erupt before the first premolars (Fig. 34-76). If this is the case, the orthodontist might elect to extract the primary canines and first molars and FIGURE 34-74 enucleate the first premolars. This is acceptable if absolutely no opportunity exists to place fixed appliances at the completion of serial extraction. Otherwise, an alternative to enucleation is almost always preferable (see group F).

Step 1: Extraction of primary canines and primary first molars and enucleation of the first premolars Step 2: Mechanotherapy (Fig. 34-77). The patient is now ready for the appliance treatment. Step 3: Retention Group F: Alternative to Enucleation. When the permanent canines are erupting ahead of the first premolars, enucleation of the premolars should be avoided if an opportunity exists to place fixed appliances at the completion of serial extraction (Fig. 34-78). When the first premolars have attained one half their root length, the primary first molars should be extracted. FIGURE 34-75

Step 1: Extraction of the primary first molars Step 2: Extraction of the primary maxillary canines, maxillary should extract the offending tooth (Fig. 34-79). However, first premolars, and primary mandibular second molars. this sequence is usually not necessary in the maxillary About 6 to 9 months later, when the emerging mandibu- dentition. lar first premolar appears to be obstructed by the mesial Step 3: Extraction of the mandibular first premolars. When these contour of the primary second molar, the orthodontist teeth emerge sufficiently, they are extracted (Fig. 34-80). CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e37

FIGURE 34-76

FIGURE 34-77

FIGURE 34-78

Step 4: Mechanotherapy. With this particular sequence, the least Group G: Interproximal Reduction. Rarely should the mesial desirable extraction result is achieved (Fig. 34-81). However, surfaces of the primary canines be reduced. These rare extraction does not prolong the fixed appliance treatment occurrences include when the practitioner does not intend to significantly. extract the permanent teeth and where a localized interference Step 5: Retention results in rotation of the lateral incisor. 997.e38 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FIGURE 34-79

FIGURE 34-80

FIGURE 34-81

Occasionally, in nonextraction malocclusions, the primary premolars after the permanent canines have emerged (Fig. second molars will be retained for an unusually long time. 34-82, B). In each instance, the mesial surface of the primary Because these teeth are wider mesiodistally than the underlying second molars should be reduced by the amount of the leeway second premolars, they force the first premolars into a forward space. This usually results in a favorable alignment of the per- position in the dental arch and thus influence the permanent manent teeth (Fig. 34-83). canines (Fig. 34-82, A). The long retention of these primary The orthodontist may find it necessary at times to reduce second molars also may interfere with the eruption of the first the distal surfaces of the primary second molars (Fig. 34-84) CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e39

A FIGURE 34-84 Reduction of the distal surface of the primary second molar to convert a straight terminal plane into a mesial step.

with the missing tooth or teeth. Whether the teeth are missing as a result of injury, disease, or developmental aberration matters little. Which teeth are missing and what is left to work with are the important factors in total correction of the malocclusion. Maxillary Incisors. The maxillary lateral incisors are frequently missing or malformed. The percentage varies depending on the study consulted but in most practices is about 5% of the patients treated. If a maxillary lateral incisor is congenitally absent, the den- B tition should be allowed to emerge completely before fixed appliance treatment begins. The orthodontist and primary care FIGURE 34-82 Interproximal reduction of the primary second dentist should examine the crown of the canine carefully after molar to allow for emergence of the permanent canine (A) and emergence before deciding to place it in the lateral incisor posi- the first premolar (B). tion or its usual position.49 The orthodontist should not rely on radiographs to evaluate the shape of unerupted teeth. Placing implant or fixed bridge restorations rather than using canines as lateral incisors may be needed if the size discrepancy exceeds the ability to restore the cuspid to appear as a lateral incisor. When canines are used as laterals, the orthodontist needs to be aware of arch size discrepancies between the arches and the potential to develop interproximal spaces during the retention period; in many instances, aesthetic considerations are the final deciding factor on whether or not to proceed with cuspid substitution.50–52 Mandibular Incisors. The patient in Figure 34-85 was treated by extraction of the mandibular central incisors. Such extraction disturbs arch length balance. Patients who have severe recession and malposition of the central incisors can be treated by routine serial extraction. The extraction of mandibular incisors, especially during development, definitely is not recommended; FIGURE 34-83 Favorable alignment after reduction of the pri- it complicates the total treatment plan and necessitates a mary second molar. compromise result. Every effort should be made to maintain the mandibular incisors, especially in unilateral situations. Sometimes the orthodontist is faced with a single missing to ensure conversion of a straight terminal plane into a mesial lower incisor. To repeat, every effort should be made to main- step in preparation for a Class I relationship of the permanent tain the mandibular incisors, especially in the unilateral situa- first molars. This is accomplished when the primary maxillary tion and during development. If one of the mandibular incisors second molars are exfoliated before those in the mandible and is missing, it may be advisable to avoid extracting a premolar when space is present to allow the molars to move mesially. in that quadrant and use the canine as an incisor. If it is an Ideally, the mandibular molars should be lost first. (For more extraction case, the molars on the affected side will be in a Class detailed discussion of interproximal reduction of primary teeth, I relationship; if it is not, they will be in a Class III relationship. read the articles by Hotz,3 Northway,46,47 and Valencia et al.48). Group H: Congenital Absence. Of utmost importance in PREMOLARS patients with congenital absence of some teeth is to proceed with the conventional orthodontic diagnosis and treatment planning Figure 34-26 illustrates a patient who had two maxillary first as if the teeth were present. Then treatment may proceed to cope premolars missing. The clinical appearance that resulted was 997.e40 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

AB FIGURE 34-85 A and B, Alignment of the mandibular dentition after treatment in a patient with congenital absence of two incisors. The first premolars were extracted in the maxilla. unusual. The canines erupted into the premolar locations, and area is corrected by using a fraction of the extraction space and the primary canines were retained. The treatment plan was without producing an alveolodental retrusion. It is difficult to altered to include extraction of the primary canines and move- encourage the emergence of second premolars ahead of the first ment of the permanent canines forward into their proper posi- premolars by extraction of the primary second molars early. tion with a resultant. Second premolars are notoriously slow in their eruption. Fur- Class II Molar Relationship. Mandibular second premolars thermore, if the primary second molars are extracted early, the frequently are missing. Depending on the basic orthodontic permanent first molars may move mesially too rapidly. Second diagnosis, treatment may involve moving the molars forward or premolars are extracted when they have emerged partially into replacing the missing teeth with implants or bridges. Treatment the oral cavity. for Class II malocclusions that involved extractions may Often the question is asked about creating a dished-in include moving the maxillary protruding incisors into the space face as the ultimate result of serial extraction when the four provided by the extraction of the maxillary first premolars. first premolar teeth are extracted. All orthodontists should be Correction for a Class II molar relationship may involve moving concerned about creating dished-in faces. That is why serial the mandibular molars forward into the second premolar area, extraction should be done only on a specific group of patients and where the teeth are congenitally absent. only after a comprehensive diagnosis. Because of this concern, the Mandibular second premolars constantly present difficulties clinician should monitor the position of the mandibular inci- in orthodontic treatment. They often are missing or erupting in sors constantly. These should be allowed to tip lingually to the the wrong direction and often are badly shaped with the poten- desired position and then held. tial for a size difference from the left to right side. The use of Some patients have a dished-in profile whether treated by TADs to bring lower molars mesially without taxing anterior extraction or nonextraction or left untreated. They exhibit a anchorage allows for space closure without adverse lingual tip- maxillary and mandibular alveolodental retrusion, a low MPA, ping of the lower incisor teeth. a deep overbite of the incisor teeth, a short anterior facial height, When one mandibular second premolar is congenitally a prominent chin, a prominent nose, and a tense perioral mus- missing, the clinician should proceed with serial extraction as culature. If a severe tooth size–jaw size discrepancy is superim- normally done, extracting all four primary canines or primary posed, extraction may be called for to produce a stable result. first molars, depending on the development. When the four Deferring consideration of extraction until all the permanent first premolars have emerged, three of them are extracted. In teeth have emerged is usually advisable with this facial pattern a quadrant where the second premolar is missing, the primary rather than performing serial extraction. If the orthodontist second molar is extracted. The first premolar then is moved performs serial extraction, the orthodontist must use extreme into the second premolar site. This allows space for the canine caution and use holding appliances.42,54,55 to emerge. Occasionally, the primary second molar must be A word of caution is necessary at this point regarding holding extracted earlier to allow the first premolar to emerge into a appliances, the labial upright positioning of permanent mandib- more distal position. ular incisors, and the distal movement of permanent mandibular Garn and Lewis53 have shown that in a congenital absence first molars by the use of fixed appliances including lip bumpers. patient, more often than not, the treatment will not require Even the use of a lower fixed lingual arch can result in the impac- extraction. In other words, congenital absence of teeth is related tion of the erupting mandibular second molars, another reason to small teeth; thus, serial extraction is not indicated. for continued monitoring during tooth eruption. If the diagnosis indicates the extraction of four second premolars or if the four teeth are congenitally missing, serial Typical Patient for Class I Serial Extraction extraction is not indicated. Second premolar extractions are A typical Class I malocclusion with an anterior discrepancy prescribed for a borderline tooth size–jaw size discrepancy in manifested by an alveolodental protrusion and a posterior dis- which the incisors are upright over basal bone. With extraction crepancy manifested by a high-angle configuration is illustrated of the second premolars, the minimal crowding in the anterior by patient M.R. (Figs. 34-86 and 34-87). The dentition when CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e41

A B

C D

E F

G H FIGURE 34-86 Patient M.R. A, At initial examination. The primary canines have been extracted. B, After extraction of primary first molars. C, Before extraction of the first premolars. D, Emergence of the permanent mandibular canines. E, Emergence of the second premolars. F, Before fixed appliance treatment. G, After fixed appliance treatment. H, Fifteen years after treatment. I, Response during interceptive guidance. J, Considerably less response during edgewise treatment. K, Response as indicated by the five cephalometric tracings 1–5( ) that were taken in each step in the treatment: 1, before treatment; 2, after extraction of the primary canines; 3, after extraction of the primary first molars; 4, after extraction of the first premolars; and 5, after fixed appliance treatment. 997.e42 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

MR MR 1 vs 4 4 vs 5

Interceptive guidance Serial extraction Edgewise treatment IJ

MR 1 2 3 4 5

Total treatment K FIGURE 34-86—CONT’D the patient came for examination and consultation is presented fixed appliance treatment (see Fig. 34-86, F). Figure 34-86, G, in Figure 34-86, A. The primary canines already had been illustrates the end result, and H, the occlusion 15 years after extracted. In such patients, the clinician extracts the primary retention. Cephalometric radiographs were taken of patient first molars to encourage the emergence of the first premolars M.R. at the following times: so that they can be extracted as early as possible. This corrects 1. Before treatment the alveolodental protrusion by upright positioning of the inci- 2. After extraction of the primary canines sor teeth. 3. After extraction of the primary first molars With a relatively straight alignment of the incisor teeth, one 4. After extraction of the permanent first premolars does not need to extract the primary canines early. In Figure 5. After edgewise treatment 34-86, B, the primary first molars have been extracted. Note The response to serial extraction during interceptive guid- the early eruption of the maxillary first premolar. A large res- ance—superimpositions of cephalometric tracings numbers toration and a periapical infection of the primary molars pos- 1 and 4 (see Fig. 34-86, I)—is significantly greater than the sibly were factors in this situation. The orthodontist should response during the edgewise treatment—superimposition of wait until the other premolars have emerged into the oral cav- cephalometric tracings 4 and 5 (see Fig. 34-86, J). ity before advising extraction of these teeth (see Fig. 34-86, Figure 34-86, K, illustrates the response during the total treat- B). Note that in Figure 34-86, C, the four premolars have ment: interceptive guidance and edgewise appliance. The mandib- been extracted, and the incisor teeth are beginning to become ular incisors gradually move upright, reducing the alveolar dental upright over basal bone. In Figure 34-86, D, the permanent protrusion; the mandibular molars move upward and forward, mandibular canines are beginning to emerge into the oral cav- accounting for an upward and forward rotation of the mandible. ity. Note that the maxillary right primary second molar has Figure 34-87 presents the facial appearance before and after been lost early. The premolar has emerged, and the first molar serial extraction and fixed appliance treatment. Note that this has drifted somewhat mesially. In Figure 34-86, E, all the pri- patient before treatment has a moderate high-angle facial pat- mary second molars have now been lost, and the second pre- tern and alveolodental protrusion. After treatment the facial molars are emerging. Note the further upright positioning of configuration exhibits harmony and balance. The smile has the incisor teeth. With the emergence of the permanent max- improved after serial extraction and again after multibanded illary canines and second molars, this patient is now ready for treatment. Balance and harmony persist 15 years after treatment. CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e43

A B

C D

E F

G H FIGURE 34-87 Facial appearance of patient M.R. Before (A and B) and after (C and D) serial extraction. E and F, After the fixed appliance treatment.G and H, Fifteen years after treatment. Cephalometric analysis of M.R. I, Before serial extraction. J, After serial extraction. K, After fixed appliance treatment. ANB, A point–nasion–B point; FMIA, Frankfort mandibular incisor axis angle; IMPA, incisor mandibular plane angle; OP, occlusal plane; SNA, sella-nasion-subspinale; SNB, sella-nasion-supramentale; Z, Z angle. The angle between the Frankfort Plane and Z Line (a line tangent to the chin and the vermilion border of both lips). 997.e44 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis

FMA 31° IMPA 91° FMIA 58° FMA 27° OP 13° IMPA 88° Z 57° FMIA 65° SNA 78° OP 8° SNB 75° Z 71° ANB 3° SNA 80° SNB 78° ANB 2° IJ

FMA 25° IMPA 86° FMIA 69° OP 7° Z 75° SNA 80° SNB 79° ANB 1°

FIGURE 34-87—CONT’D

Before treatment, the cephalometric analysis of patient reduction in the FMA and the IMPA and a favorable rota- M.R. showed an FMA of 31 degrees. This represents a high- tion of the mandible and correction of the alveolodental pro- angle face. Throughout the course of serial extraction, the trusion. The reduction of the OP angle from 13 to 8 degrees FMA was reduced to 27 degrees and throughout the course during serial extraction indicated a mesial migration of the of fixed appliance treatment to 25 degrees. The 6-degree posterior teeth and an upright positioning of the mandibular reduction indicated a favorable upward and forward rotation incisor teeth, both favorable responses in the treatment of this of the mandible. The patient’s IMPA before treatment was particular facial pattern. The reduction of the OP angle from 91 degrees, suggesting a moderate alveolodental protrusion 8 to 7 degrees during active treatment indicated good con- for a high-angle facial pattern. During serial extraction, the trol. The overall increase in the Z angle of 18 degrees (from 57 mandibular incisors were positioned upright to 88 degrees to 75 degrees) reflected a favorable rotation of the mandible and during active treatment to 86 degrees. This reduction of and correction of the alveolodental protrusion. The maxilla 5 degrees in the IMPA resulted in a slightly more balanced grew slightly during the serial extraction period from 78 to and harmonious soft tissue profile. The overall increase in 80 degrees and remained relatively constant during active the FMIA of 11 degrees (from 58 to 69 degrees) reflected a treatment. Mandibular growth and rotation accounted for CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis 997.e45

3 degrees during the serial extraction period and for 1 more growth area: FMA = 31, ANB = 3, Z angle = 57, OP = 13, degree during the active period of treatment. Throughout SNB = 75, and PFH/AFH = 0.65. total treatment, the ANB was reduced from 3 degrees to 1 After serial extraction (see Fig. 34-88, B), all six measure- degree, indicating a modest improvement in the jaw relation- ments were within the normal range: FMA = 27, ANB = 2, Z ship (see Fig. 34-87, I–K). Important in patient M.R.’s case was that the tooth size– jaw size discrepancy not be corrected by extension of the teeth Retrognathic Prognathic posteriorly, anteriorly, laterally, or vertically. If this had been highO lowO done in such a high-angle facial pattern, the molar extrusion vertical growth horizontal growth would have resulted in an unfavorable downward and backward rotation of the mandible. With extrusion of the molars FMA 28 27 26 25 24 23 22 and the dumping forward of the incisors, the OP would have ANB 5 4 2 1 been tipped unfavorably and the alveolodental protrusion worsened. With the mandibular rotation and the tipped OP, Z 70 71 72 73 74 75 76 77 78 79 80 the maxillary incisor would have been rabbited downward and 12 11 10 9 8 backward, revealing more gingival tissue. Concomitant effects OP include impaction of the posterior molars and expanded den- SNB 78 79 80 81 82 tal arches. Furthermore, the mandibular incisors would have PFH/AFH 67 68 69 70 71 72 been tipped off basal bone, creating an unstable situation that Before serial required prolonged retention. The harmony and balance of extraction 56 the facial profile could have been worsened considerably. age 8.5 yrs The total space analysis indicated an anterior and posterior A space discrepancy. The anterior discrepancy was corrected by serial extraction and extraction of the permanent first premo- Retrognathic Prognathic lars. The posterior discrepancy was corrected by extraction of highO lowO vertical growth horizontal growth the permanent third molars. FMA 28 27 26 25 24 23 22 KEY MEASUREMENTS FOR DIAGNOSIS AND ANB 5 4 2 1 CASE EVALUATION Z 70 71 72 73 74 75 76 77 78 79 80 The Tweed Foundation has conducted several studies on 12 11 10 9 8 the difference between successful and unsuccessful treat- OP ment.57–63 They have indicated six measurements that are SNB 78 79 80 81 82 crucial in the evaluation of this difference: FMA, ANB, Z angle, OP, sella-nasion-supramentale (SNB), and the ratio of PFH/AFH 67 68 69 70 71 72 the posterior face height–to–anterior face height ratio (PFH/ After serial AFH) (Box 34-1). We have designed a “wiggle” to illustrate extraction age 12.5 yrs successful treatment (Fig. 34-88). Patient M.R.’s six mea- B surements before serial extraction (see Fig. 34-88, A) were to the left of the wiggle, in the retrognathic, high-angle vertical Retrognathic Prognathic highO lowO vertical growth horizontal growth BOX 34-1 Six Crucial Measurements for 28 27 26 25 24 23 22 Treatment Success FMA 5 4 2 1 FMA (Frankfurt mandibular plane angle) Indicates mandibular ANB response. In most patients, successful treatment is associated with a Z 70 71 72 73 74 75 76 77 78 79 80 favorable counterclockwise rotation indicated by a reduction of FMA. ANB (A point–nasion–B point) angle Indicates the correction of a skel- OP 12 11 10 9 8 7 etal discrepancy. Successful treatment is associated with a reduction in ANB in most instances. SNB 78 79 80 81 82 Z angle Indicates the alveolar dental and soft tissue profile response. 67 68 69 70 71 72 With successful treatment, improvement in the soft tissue balance and PFH/AFH harmony and reduction in the alveolar dental protrusion occur. This is After active associated with an increase in the Z angle. treatment OP (occlusal plane) Indicates the control of treatment. If the mandibular age 14 yrs molars are prevented from extruding and the mandibular incisors are not C “dumped” forward, the occlusal plane does not tip forward. If anchorage FIGURE 34-88 A, The graphic “wiggle” for patient M.R. before is prepared and the incisors are positioned upright, the OP decreases. Successful treatment is associated with a flattening of the OP. serial extraction. B, The wiggle for patient M.R. after serial SNB (sella-nasion-supramentale) angle Indicates the mandibular extraction. C, The combined graphic wiggle for patient M.R. response. In most patients, if the treatment is successful, the SNB angle Note the improved measurements after both serial extraction will increase. and fixed appliances.ANB, A point–nasion–B point; FMA, PFH/AFH (posterior facial height/anterior facial height) Indicates the Frankfurt mandibular plane angle; OP, occlusal plane; PFH/ANH, mandibular response. In successful treatment the PFH increases rela- posterior face height–to–anterior face height ratio; SNB, sella- tively more than the AFH; therefore, the ratio increases. nasion-supramentale; Z, Z angle. 997.e46 CHAPTER 34 Interceptive Guidance of Occlusion with Emphasis on Diagnosis angle = 71, OP = 8, SNB = 78, and PFH/AFH = 0.69. Clini- 17. Burlington Orthodontic Research Project. University of Toronto: Faculty of cally, this is a highly successful response, especially without Dentistry, report no. 3; 1957. mechanotherapy. 18. Yoshihara T, Matsumoto Y, Suzuki J, et al. Effect of serial extraction alone After edgewise treatment (see Fig. 34-88, C), the measure- on crowding: relationships between tooth width, arch length, and crowding. Am J Orthod Dentofac Orthop. 1999;116:691–696. ments increased slightly but remained within the normal range, 19. Yoshihara T, Matsumoto Y, Suzuki J, et al. Effect of serial extraction alone except for one reading, the OP, which was overcorrected slightly. on crowding: spontaneous changes in dentition after serial extraction. Am When facial deformity has been corrected and mental J Orthod Dentofac Orthop. 2000;118:611–616. 20. Moorrees CF. Changes in dental arch dimension expressed on the basis of anguish eliminated, a dull and unhappy facial expression tooth eruption as a measure of biologic age. J Dent Res. 1965;44:129. becomes bright and happy. What greater reward could any 21. DeKock WJ. Dental arch depth and width the studies longitudinally from orthodontist want or expect? 12 years of age to adulthood. 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The effect of the extraction of lower first Tweed CH. The Frankfort-mandibular plane angle in orthodontic diagnosis premolars on the migration of teeth in the human dental arch. J Dent Res. classification, treatment planning, and prognosis. Am J Orthod Oral Surg. 1979;58:1252–1256. 1946;32:175. Rousset MM, Boualam N, Delfosse C. Occlusion and rhythm of eruption. Bull Tweed CH. The Frankfort-mandibular incisor angle in orthodontic diagnosis, Group Int Rech Sci Stomatol Odontol. 2001;43(2):53–61. treatment planning, and prognosis. Angle Orthod. 1954;24:121. Saatçi P, Yukey F. The effect of premolar extractions on tooth-size discrep- Tweed CH. Pre-orthodontic guidance procedure, classification of facial ancy. Am J Orthod Dentofac Orthop. 1997;111:428–434. growth trends, treatment timing. In: Kraus BS, Riedel RA, eds. Vistas in Sanin C, Savara B, Sekiguchi T. Longitudinal dentofacial changes in untreated Orthodontics. Philadelphia: Lea & Febiger; 1962. persons. Am J Orthod. 1969;55:135. Vaden JL, Kiser HE. Straight talk about extraction and non extraction: a dif- Schirmer UR, Wiltshire WA. Manual and computer-aided space analysis: a ferential diagnostic decision. Am J Orthod Dentofac Orthop. 1996;109:445– comparative study. Am J Orthod Dentofac Orthop. 1997;112:676–680. 452. Schudy FF. The rotation of the mandible resulting from growth: its implica- Wagers LE. Preorthodontic guidance and the corrective mixed-dentition tions in orthodontic treatment. Angle Orthod. 1965;35:36. treatment concept. Am J Orthod. 1976;69(1):1–28. Sharpe W, Reed B, Subtelny JD, et al. Orthodontic relapse, apical root resorp- Wagner M, Berg R. Serial extraction or premolar extraction in the permanent tion, and crestal alveolar bone levels. Am J Orthod. 1987;91:252–258. dentition? Comparison of duration and outcome of orthodontic treat- Shearer DH, Woodside DG. Postretention mandibular incisor stability in serial ment. J Orofac Orthop. 2000;61(3):207–216. premolar extraction cases. Am J Orthod. 1995;107(4):459. Wasserstein A, Shalish M. Adequacy of mandibular premolar position despite Slaj M, Jezina MA, Lauc T, et al. Longitudinal dental arch changes in the mix early loss of its deciduous molar. J Dent Child. 2002;69(3):233–234, dentition. Angle Orthod. 2003;73(5):509–514. 254–258. Staggers JA. A comparison of results of second molar and first premolar Watanabe CT, Watanabe JI, Taguchi T, et al. Eruption disturbances of man- extraction treatment. Am J Orthod Dentofac Orthop. 1990;98(5):430–436. dibular permanent incisors. J Clin Pediatr Dent. 2001;25(3):181–185. Staggers JA. Vertical changes following first premolar extractions. Am J Orthod Weinberg MA, Eskow RN. An overview of delayed passive eruption. Compend Dentofac Orthop. 1994;105(1):19–24. Contin Educ Dent. 2000;21(6):511–514. Stahl F, Grabowski R. Maxillary cine displacement and genetically determined Wilson JR, Little RM, Joondeph DR, Doppel DM. (1999) Comparison of soft predisposition to disturbed development of the dentition. J Orofac Orthop. tissue profile changes in serial extraction and late premolar extraction. 2003;64(3):167–177. Angle Orthod. 1999;69(2):165–172. Steyn CL, Harris AM, du Preez RJ. Anterior arch circumference: how much? Wise GE, Frazier-Bowers S, D’Souza RN. Cellular, molecular, and genetic Angle Orthod. 1996;66:457–461. determinants of tooth eruption. Crit Rev Oral Biol Med. 2002;13(4):323– Surbeck BT, Artun J, Hawkins NR, et al. Association between initial post treat- 334. ment and postretention alignment of maxillary anterior teeth. Am J Orthod Yamaguchi K, Nanda RS. The effects of extraction and nonextraction Dentofac Orthop. 1998;113:186–195. treatment on the mandibular position. Am J Orthod Dentofac Orthop. Taguchi Y, Yano Y, Kobayashi H, et al. Retarded eruption of maxillary second 1991;100(5):443–452. premolars associated with late development of the germs. J Clin Pediatr Yang EY, Kiyak HA. Orthodontic treatment timing: a survey of orthodontists. Dent. 2001;25(3):175–179. Am J Orthod Dentofac Orthop. 1998;113:96–103. Takanobu H, Little RM. Early versus late treatment of crowded first premolar Yoshihara T, Matsumoto Y, Suzukui J, et al. Effect of serial extraction alone on extraction cases: post retention evaluation of stability and relapse. Angle crowding: spontaneous changes in dentition after serial extraction. Am J Orthod. 1998;68:61–68. Orthod Dentofac Orthop. 2000;118(6):611–616. Tanner JM. Growth at Adolescence. 2nd ed. Cambridge, MA: Blackwell Scien- Yoshihara T, Matsumoto Y, Suzukui J, et al. Effect of serial extraction alone tific; 1962. on crowding relationship between closure of residual extraction space and Toshniwal NG. A review of serial extraction. J Indian Dent Assoc. 1990;61(12):291. changes in dentition. J Clin Pediatr Dent. 2002;26(2):147–152. 35

Functional Appliances

Thomas M. Graber*

OUTLINE Origin, 997.e50 Fränkel Appliance, 997.e68 Andresen Activator, 997.e51 Double Plates, 997.e69 Bite-Opening Controversy, 997.e53 Clark Twin Block Appliance, 997.e70 Head Posture during Sleep, 997.e53 Magnetic Appliances, 997.e71 Working Hypotheses, 997.e54 Stöckli-Teuscher Combined Activator-Headgear Sagittal Change, 997.e54 Orthopedics, 997.e75 Vertical Opening Variations, 997.e56 Fixed Functional Appliances, 997.e81 Mechanisms of Class II Correction with Functional Herbst Appliance, 997.e81 Orthopedics, 997.e57 Sagittal Changes, 997.e85 Class II Correction: A Likely Scenario, 997.e59 Vertical Changes, 997.e85 Bionator, 997.e59 Long-Term Posttreatment Changes, 997.e88 Construction Bite, 997.e62 Jasper Jumper, 997.e90 Anterior Mandibular Posturing, 997.e63 Summary, 997.e92 Hamilton Expansion Activator, 997.e64

the raison d’être for this tissue reaction, and the reader should This “Classic Chapter in Orthodontics” is taken from our become familiar with the minutiae to better understand import- fourth edition of Orthodontics: Current Principles and Tech- ant factors such as the way appliances work, the best time to use niques published by Elsevier in 2005. It is presented as then them, and their limitations. An orthodontic practitioner cannot written. The chapter contains perspectives and information help but be excited by the prospect of using the patient’s own that remain valuable to orthodontic residents and clinicians. functional forces to achieve orthopedic and orthodontic correction of dentofacial abnormalities. Indeed, previous overcon- The stomatognathic system consists of the teeth, the periodontal centration on the mechanical aspects of orthodontics has been membranes, alveolar and basal bone, the temporomandibular a barrier to the full realization of the magnitude of influence joints (TMJ), and the motivating and draping neuromuscula- that is possible. Orthodontics is not only the appliance, but it is ture. This is a living, viable, and remarkably adaptive system, about which appliances, why, when, and for how long. particularly during the period of growth and development of the craniofacial complex. Bone may be one of the hardest tis- ORIGIN sues in the human body, but it is also one of the most responsive to environmental stimuli. For example, persons have known for Theories on bone plasticity may be traced to Wolff2 and Roux,3 who many centuries that the membranous bone cranial structures believed that form and function were intimately related. Changes can be deformed by binding an infant’s skull, as was done by the in functional stress produced changes in internal bone architecture Inca Indians.1 Pathologic manifestations can result in bizarre and external shape. Recent research has supported Roux’s concept craniofacial asymmetries and deformities that involve cranial of functional “shaking of the bone,” and the anabolic stimulus and mandibular structures. Practitioners can learn much about applied to achieve the optimal morphogenetic pattern.4–6 the normal condition from pathologic conditions. Early in the twentieth century, Pierre Robin of France intro- Orthopedic surgeons have corrected skeletal endochondral duced the plastic monobloc as a passive positioning device. This deformities for many years, primarily in growing individuals. device was used in neonates with micromandibular develop- However, influencing endochondral bone is known to be a ment to prevent glossoptosis, which is literally a blocking of the greater challenge. The chapters in this book by Thilander, Hatch, airway by the tongue.7 This congenital abnormality of develop- and Sun (Chapter 3) and Roberts and Huja (Chapter 4) describe ment has been called Pierre Robin syndrome and is usually associated with cleft palate. The Robin appliance was modified from bite-jumping vulcanite maxillary anterior guide planes designed *An article in memoriam of author Thomas M. Graber can be found by Norman Kingsley.8 However, the Kingsley guide plane was at the following link: http://www.sciencedirect.com/science/article/pii/ attached to teeth, whereas Robin had to use his monobloc as a S0889540615008835 removable device because newborns have no teeth. 997.e50 CHAPTER 35 Functional Appliances 997.e51

ANDRESEN ACTIVATOR Viggo Andresen of Norway also was familiar with the writings of American authors Norman Kingsley8 and Calvin Case.9 Their use of bite-jumping appliances was common among other orthodontists at the end of the nineteenth century. Even Angle Functional Appliances originally resorted to and recommended such appliances for patients with mandibular retrusion.10 Also on Andresen’s book- shelf was a favorite of his, the orthodontic textbook of Benno Thomas M. Graber* Lischer,11 published in 1912. Lischer presented graphic illustrations of the effect of abnormal perioral muscle function on the teeth and investing tissues. One conclusion to be drawn from Lischer’s theory is that if compensatory and adaptive lip and tongue function could exacerbate excessive overjet in types of Class II malocclusions and if abnormal swallowing and prolonged finger-sucking habits could create anterior open bite and narrow maxillary arches, then could not the same muscles be used to correct these and other problems? This theory was particularly true of patients with Class II, Division 1 conditions who had protruding maxillary teeth and retrusive lower dentition, a combination that created excessive overjet and evoked compensatory, adaptive function. Why not use these same deforming muscles to reverse the procedure? Holding the mandible forward long enough could reverse the deleterious effects of a trapped lower lip, lack of normal lip contact, and abnormal res- FIGURE 35-1 Andresen-Häupl activator. This device has no piration, characteristics associated with malocclusion and illus- tooth-moving parts. The appliance was made to treat Class II, trated as early as 1861 by artist George Catlin (cited in Angle12.) Division 1 malocclusions. Instead of palatal coverage, a heavy Actually, Andresen was not thinking of “guiding growth” at Coffin spring has been used to ensure stability and yet allow that time but only of eliminating the adverse effects of abnormal tongue contact with the mucosa. The loops in the canine region function. This working hypothesis was tested on his own daugh- stand away from the teeth, allowing maxillary intercanine devel- ter, who was wearing fixed orthodontic appliances and who was opment. These loops are the forerunners of the Balters Bionator going away to camp over the summer. Andresen removed the screening loops, which extend to the distal aspect of the decidu- fixed appliances and placed a modified Hawley-type retainer on ous second molar, and also of the Fränkel buccal shields, which the maxillary arch. However, he added a lingual horseshoe flange are also meant to hold off cheek pressure. (From Andresen V, that guided the mandible 3 to 4 mm forward when the teeth Häupl K. Funktionskieferorthopädie: die Grundlagen des “Norwe- were brought into maximal closure allowed by the interposed gischen Systems.” 2nd ed. Leipzig, Germany: H Meusser; 1936. acrylic guide plane13–16 (Fig. 35-1), which was done to prevent any relapse over the 3-month vacation period. On his daughter’s the appliance had an added benefit; it was thought to serve as a return, Andresen was surprised to see that nighttime wearing of night guard, preventing the potentially deleterious effects of noc- the appliance not only eliminated the abnormal neuromuscular turnal parafunctional activity, actually stimulating normal muscle compensations, but it also produced a complete sagittal cor- activity and enhancing the metabolic pump activity of the retro- rection and significantly improved the facial profile. The result diskal pad. This repetitive pump activity increased blood flow was stable. When trying this system on numerous other growing into the highly vascular posterior attachment on guided man- patients who were going away for the summer and then on patients dibular protraction and forced out the catabolic by-products on undergoing routine care throughout the year, Andresen observed mandibular retraction.64,65 The obvious benefits of a protracted, significant sagittal basal bone and neuromuscular improvement unloaded condyle were hypothesized to be enhancement of con- that he had not been able to achieve with devices such as conven- dylar growth increments and a more favorable upward and back- tional fixed appliances and intermaxillary elastics.14 ward condylar growth direction.4 Fundamental tissue research The sagittal changes that Andresen observed occurred because by Bierbaek and colleagues,66 Braun and associates,67 Buschang the appliance increased the activity of the protractor and eleva- and Santos-Pinto,24 Chen and others,68 Decrue and Wieslander,69 tor muscles, with concomitant relaxation and stretching of the Droel and Isaacson,70 Du and colleagues,27 El-Bialy and associ- retractors. The elimination of the abnormal perioral muscle ates,71 Garattini and others,72 Graber,65 Ikai and colleagues,32 function by mandibular protraction prevented the deforming Kantomaa and Pirttiniemi,34 McNamara and associates,43 and restrictive action of the trapped lower lip and the hyperactiv- Pancherz,47 Paulsen,49,50,73 Pirttiniemi and others,51 Popowich ity of the mentalis and submandibular muscle groups (Figs. 35-2 and colleagues,74 Rabie and associates,75 Ruf and Pancherz,53 and 35-3). Compensatory mandibular opening caused by con- Vardimon and others,76 Voudouris and colleagues,77–79 Ward comitant mouth breathing also could be eliminated. The change and associates,80 Watted and others,61 Woodside and colleagues,81 in muscle pattern would thus produce not only a new and more and Xiong and associates82 stresses the changing position of the favorable pattern but also a change in bony structures as the mus- glenoid fossa during growth and the potential for influencing it, cles adapted to the new functional stresses (Fig. 35-4).6,17–63 even as the Incas changed growth eons ago. The intermittent forces produced by the loose appliance were As with Robin’s monobloc, Andresen’s first appliances thought to create favorable changes in tooth position, even though were passive, having no intrinsic force systems. Only when the the appliance was worn only at night. Later, it was postulated that patient bit into the appliance would the extrinsic force be in 997.e52 CHAPTER 35 Functional Appliances

FIGURE 35-2 Construction bite. Correcting the buccal segment relationships from Class II to Class I is accomplished through mandibular advancement of approximately 6 mm. Note that the overjet is still excessive because of labially malposed maxillary incisors, which can be corrected after the buccal segment relationship has been normalized. An interocclusal clearance of 3 to 4 mm allows the mandible to come forward sufficiently to correct the buccal segment intercuspation. (Redrawn from Andresen V, Häupl K. Funktionskieferorthopädie: die Grundlagen des “Nor- wegischen Systems.” 2nd ed. Leipzig, Germany: H Meusser; 1936.)

FIGURE 35-3 Lateral view of study models of the patient in Figure 35-2, a severe Class II, Division 1 malocclusion. The lingual inclination of the lower incisors is a favorable condition for functional therapy, as is the deeper-than-normal overbite. (From Andresen V, Häupl K. Funktionskieferortho- pädie: die Grundlagen des “Norwegischen Systems,” 3rd ed. Leipzig, Germany: JA Barth; 1942.)

A B FIGURE 35-4 Profile with jaws in habitual Class II occlusion. A, Note the improvement when the mandible is protracted into a Class I relationship. B, The patient has a tendency to elevate the head when protruding the mandible, a maneuver that frees the airway. effect. The growth increments were hypothesized to be greater teaming up with Karl Häupl and doing further work on the at night, a belief that later was validated by Hotz,83 Igarishi and concepts and technique refinements, was the name changed colleagues,84 Korkhaus,85 and Petrovic and associates.86 to functional jaw orthopedics, which was more descriptive.10,15 The original name Andresen used for this type of treat- The concepts were broadened to include the potential for ment was biomechanical orthodontics. Only later, after altering skeletal relationships, depending on the amount and CHAPTER 35 Functional Appliances 997.e53

direction of jaw growth. The forward posturing of the mandible, as determined by the carefully manipulated construction bite, was reasoned to produce beneficial sagittal skeletal change by harnessing the growth potential. This was a contra- diction of early bite-jumping procedures, which were deemed strictly positional changes of the mandibular condyle in the fossa; hence, the functional orthopedic connotation. The treatment became known as the Norwegian system to much of the orthodontic world, although Andresen was a Dane and AB Häupl was a German (both taught at the dental school in FIGURE 35-5 Various forces act on the upper and lower arches. Oslo, Norway).87 In this case, the influence of gravity is different when the head is erect (A) than during sleep when the head is turned to one BITE-OPENING CONTROVERSY side or another (B). In the latter case, the activator tends to prevent the normal change or adaptation to varying postural and Although the concept of sagittal construction bite advance- gravitational forces that elicits a positive reaction from the orofa- ment was generally accepted by clinicians in Europe (it varied cial muscles, particularly the protracting and retracting muscles. from 3 to 6 mm, depending on the severity of the anteropos- Because the patient swallows only four to eight times an hour terior dysplasia and the resultant abnormal buccal segment during sleep, this positive reaction is more likely responsible for interdigitation), the theory pertaining to the amount of ver- any changes effected by the appliance. (From Herren P. The tical opening and its effect on the muscles produced consid- activator’s mode of action. Am J Orthod 1959;45:512–527. With erable controversy. Selmer-Olsen,8 who became professor of permission from the American Association of Orthodontists.) orthodontics at the University of Oslo after World War II, believed that the muscles could not actually be stimulated during sleep; nature had designed them to rest at night, and Head Posture during Sleep swallowing occurred only four to eight times an hour. He inter- Another variable is the many changes of head posture that preted the activator action as stretching of the muscles, fascial occur during sleep, altering the magnitude and direction of sheets, and ligaments when the mandible was opened beyond force.91 At any particular moment, the mandibular rest position the postural resting position (i.e., viscoelastic response). In depends on the head and body posture; therefore the restriction truth, the activator was a foreign body, and the tooth-moving of muscle movement required to create the desired mandibular force produced did not result from the kinetic energy of mus- position change without the activator in place constantly varies, cle function but from the potential energy of stretched tissues. involving different muscle groups and creating different force Woodside and colleagues81,88 called this the viscoelastic prop- vectors on the activator (see Fig. 35-5). The plane of sleep (light erties of the tissues. Current debate on the precise nature of or deep), the intraoral air pressure, the dream cycle, and the the activator effect still reflects the divergence of opinion.89 state of mind are additional conditioning factors, all uncon- According to Lysle Johnston,90 condylar unloading is a fac- trolled by the clinician. Only the mandibular position (and the tor. Research by Graber4,64 indicates that enhanced metabolic potential effect on the glenoid fossa), as held by the appliance, activity, accomplished through the stretched and enlarged is controllable. However, the splinting or guiding effect on the TMJ retrodiskal pad during protraction, is a too-long-over- mandible is such that it can help influence the net effect of the looked consideration. variable forces. If the activator is properly designed and worn Andresen and Häupl’s interpretation presupposed free- as prescribed, then the result of all the controlled and uncon- dom for the mandible to assume the physiologic rest position. trolled forces is usually designed to enhance adaptation to the Slagsvold,91 later professor of orthodontics at Oslo, reported position created by the appliance (Figs. 35-6 and 35-7).6,56 that his own observations did not completely substantiate this Herren95 has tried to assess the magnitude of the resultant premise. Nevertheless, he concurred that forward posturing forces acting on the mandible and the interaction between them. should not exceed the rest position vertical opening of 2 to 4 The weight of the mandible, tongue, and appliance is constant, mm. Too wide an opening made compliance more difficult averaging approximately 250 g. Muscle tonus and tensions vary, and could produce a depressing force on the posterior teeth— depending on factors such as the degree of stretching, the con- hardly desirable in deep-bite, Class II malocclusions. Grude92 trol from the central nervous system, the relation with the bed or and Fränkel93 strongly support this construction bite limit. pillow, and whether the head is prone or supine. If the patient is Fränkel recommended incremental small advancements of 2 to dorsally recumbent while sleeping and the head is upright, then 3 mm for his appliances rather than “the great leap forward” the muscle forces must balance the weight of the lower jaw, asso- of 5 to 7 mm. Reactivation of optimal tissue response, as well ciated soft tissue structures, and appliance. The multiple forces as enhanced patient compliance, are factors. Petrovic and col- are different in prone, supine, and rotated combinations. The leagues,86 Komposch and Hockenjos,35 and McNamara and forces created are basically intermittent, however, even though associates42 provide laboratory verification of this fact. some of the teeth or groups of teeth may be subject to pressure The philosophy of Harvold94 and Woodside88 has been to for a protracted period. The loose appliance is responsible for exceed the freeway space limits, if for no other reason than to some of the intermittent action. Removal of the appliance during keep the appliance in place at night during sleep so as to main- the day also produces a net intermittent action, calling up a new tain a corrective stimulus. As for the cognitive interpretations muscle engram to establish the neuromuscular engram consis- of Selmer-Olsen, subsequent research by Ahlgren,17 Herren,95 tent with diurnal postural changes and activities.* Komposch and Hockenjos,35 Sander,54 Schmuth,96 and Wat- ted and colleagues61 corroborated the finding that the activator does not activate muscles during sleep (Fig. 35-5). * References 17, 19, 40, 45, 81, 92, 97–99. 997.e54 CHAPTER 35 Functional Appliances

back into position on the maxillary teeth when it dropped away. This hypothesis was supported by the Roux concepts. A prereq- uisite was that the bite opening should not exceed the normal interocclusal clearance or freeway space. This approach also enhanced the metabolic pumplike action of the TMJ retrodiskal pad, stimulating anabolic and catabolic exchange.4,64,72 2. The second hypothesis denies that enhanced functional activity is induced at night by the bite-opening activator and implies that the activator at rest moves the teeth and creates the desired changes. Current long-range case analysis of treated individuals shows some support for this thesis.20,21,100 AB The interocclusal mass of acrylic exceeds the physiologic FIGURE 35-6 Instead of evoking postural change in body posi- resting position. The appliance thus is squeezed between the tion during sleep (A), as in Figure 35-5, the activator splints the jaws most of the time, splinting them in the desired sagit- jaws in a more normal transverse relationship while exerting tal relationship and preventing postural changes that would pressure on specific teeth in the buccal segments (B). (Redrawn normally occur without the activator in place. The resulting from Herren P. The functional mechanism of the activator. SSO intermittent forces vary from time to time in frequency and Schweiz Monatsschr Zahnheilkd 1953;63:829–879.) magnitude, but the net result is the distribution of functional forces to the activator, which transmits them to the teeth and alveolar bone, enhancing the adaptive process. The forces produce a strain in the tissues (i.e., viscoelastic stretch) and essentially act as mechanical phenomena20,22,81,88,100 (Fig. 35-8). Normal respiration is optimized with forward mandibular posturing, particularly in young patients with excessive epipha- ryngeal tissue. This appliance thus prevents the development of open bite problems, overeruption of posterior teeth, steeper mandibular plane inclination, and compensatory tongue posture changes that might be deleterious. This hypothesis has been validated by subsequent studies by Woodside and colleagues.† No Forward Backward displacement displacement displacement Sagittal Change The forward posturing of the mandible, produced by the construction bite, creates the desired sagittal change (Fig. 35-9). This aspect depends on the desired growth guidance and adaptive processes for the skeletal and dental modifications. Occasion- ally, a functional retrusion is eliminated, particularly in deep bite malocclusions, which has long gone unrecognized because only the apparent condylar position in the glenoid fossa was used as a criterion and the more retruded fossa in Class II problems was not.66,70 Controversy still surrounds the interpretations, despite extensive research by Cevidanes and colleagues,106 Graber and associates,10 McDougall and McNamara,39 McNamara and col- 40,42 46–48,107,108 86 Displacement leagues, Pancherz, Petrovic and associates, Ruf Forward Forward 54 78,79 to the left displacement displacement and Pancherz, Voudouris and colleagues, and others.* to the right to the left These studies clearly indicate an enhancement of growth while FIGURE 35-7 The direction of forces acting on the activator at the functional appliance is worn— that is, more condylar growth any particular time depends on the spatial relationship induced increments and a change in the direction of growth to a more by postural changes. The view is from the top of the head, with upward and backward vector. Stutzmann’s research demonstrates an actual change in the internal condylar structure, with the face to the left of the ovoid outline. (Redrawn from Her- 86 ren P. The functional mechanism of the activator. SSO Schweiz a more posterior directional orientation of the trabeculae. Monatsschr Zahnheilkd 1953;63:829–879.) Some evidence also exists of minor retardation of maxillary sagittal growth.10 Vertical growth, of course, can be controlled by the interocclusal acrylic mass, preventing or allowing erup- Working Hypotheses tion of posterior teeth. As previously mentioned (and a factor For conventional nighttime wear of the classic activator, two that has been too long neglected), the change in growth direc- working hypotheses have been proposed for the effect on the tion in the fossa, as well as modification of the fossa, have both teeth themselves: been demonstrated by Decrue and Wieslander,69 Droel and 1. T he original Andresen-Häupl rationale attributed tooth move- Isaacson,70 Ikai and colleagues,32 McNamara and associates, 43 ment to a loose-fitting, functionally generated mobility that provided intermittent forces created by the elevator and protractor muscles and by the elements of the buccinator mechanism. † References 19, 81, 88, 97–99 ,101–105. These forces jolted or shook the teeth, pushing the appliance * References 18, 20, 22, 25, 31, 36, 38, 45, 49 ,50, 58, 72, 83, 109–117. CHAPTER 35 Functional Appliances 997.e55

A B FIGURE 35-8 A, When the patient is upright, muscle tension, muscle tonus, and atmospheric pressure balance the weight of the mandible, the associated tissues, and the activator. B, If the patient reclines during sleep while wearing the activator, then gravity, muscle tension, and tonus act in the same direction. However, during sleep, the lips drop open, mouth breathing ensues, and function is minimal.

FIGURE 35-9 Modifiedcephalometric tracings illustrate the immediate effect of placing a functional appliance that postures the mandible forward (arrows). The condyle is brought forward and downward on the eminence, which removes the usual functional stresses. The retractor muscles are activated, exerting some force against the maxillary arch. Reduced masseter activity is evident. (Redrawn from Fanghänel J, et al. Changing muscle activity with functional appliances. Eur J Orthod 1998;20:468.)

Pancherz,47 Paulsen,49 Ruf and Pancherz,53 Woodside and col- temporomandibular fossa with respect to the anterior cranial base. leagues,81 and others.† This component of sagittal change might be the most significant. Unfortunately, definitive incremental changes are hard Such change must occur during the growth period. Therefore sag- to measure because of the limitations of two-dimensional ittal change is a combination of incremental increases in condylar radiographic superimpositions. However, Buschang and San- growth, a more favorable direction of condylar growth, reposi- tos-Pinto24 have shown significant change in the position of the tioning and adaptation of the fossa and articular eminence, and some degree of withholding of the maxillary dentoalveolar area by the appliance, depending on factors such as the structural design, † References 9, 27, 34, 61, 64, 66, 72, 80, 100, 118. duration of wear, and possible use of an extraoral appliance.119 997.e56 CHAPTER 35 Functional Appliances

Melanson and Van Dyken,117 as well as Johnston,90 believe that mere unloading of the condyle by forward posturing can be a significant factor. This belief is based on the seminal study conducted some years ago by Melanson and Van Dyken at the University of Michigan, in which unloading the condyles in primates actually stimulated condylar growth. The results can vary, as shown by Graber120 in an analysis of 58 patients treated with the Fränkel functional regulator. When the enhanced metabolic action is coupled with neuromuscular and appliance stimulation, significant improvement can be attained during a period of active dentofacial growth that is not possible with conventional fixed mechanotherapy alone.65 The same analysis can be applied to the Herbst fixed functional appliance, as reintroduced and modified by Pancherz* (see also Graber64,121). (For an excellent discussion of this appliance and its modified versions, see Chapter 16 of Dentofacial Orthopedics with Functional Appliances, 2nd ed., by Graber and associates,122 as well as a discussion later in this chapter.) Conversely, in early FIGURE 35-10 A number of activator models (e.g., Wood- clinical reports based on minimal material and experience in the side, Herren, Harvold) require a larger vertical opening, which appliances, Creekmore and Elkund,123 Gianelly and colleagues,112 exceeds the freeway space at postural rest position and elicits and Ricketts124 noted little enhancement of mandibular length. the viscoelastic or stretch properties of the associated tissues. However, long-term studies by Ruf and Pancherz53,54 showed This illustration shows an 8-mm opening between the first an additional 1 to 2 mm of growth over the normal mandibu- molars. The lower incisors are capped to provide more stability lar growth pattern for Herbst cases. If left alone, the mandibular and to offset the tendency of these teeth to procline. length for most Class II, Division 1 malocclusions is deficient. Furthermore, in addition to some enhanced condylar proliferation, the direction of growth changes to a more upward and The current use of skeletal design functional appliances backward vector for the condyle. Finally, significant glenoid fossa mostly follows the original small opening, incremental sagittal adaptation and positional change occurs, as previously noted.† advancement concept, and encourages daytime wear. The fre- Elimination of neuromuscular perversions that accentuate the quency of deglutition is increased, and phasic muscle activity overjet could be a significant factor in the ultimate status. This is enhanced. Thilander and Filipsson59 conducted electromyo- is too often ignored by “one phase, get in–get out” philosophies. graphic studies on daytime wear and found an insignificant The net effect is that these patients attain the achievable optimum increase in muscle forces when no active function occurred. of pattern, assuming that treatment is timed to coincide with the During mandibular activity, however, increased force was period that has the greatest growth and developmental potential exerted, especially by the retracting muscles. Increased deglu- for sagittal correction. Although such appliances can be used in titional activity also was associated with the enhanced sali- a patient who is past the maximal growth period, more dentoal- vary flow. Sander55 and Schmuth96 have also studied the role veolar response and more likelihood of proclination exist in the of functional appliances. Their research indicates that patients lower incisors.22,57,95,126–129 The correct comparisons of treated with large protrusive construction bites tend to disclude the functional cases are made not with a normal sample but with appliances during the day and at night, reducing the desired comparable untreated patients of the same age, pattern, gender, effect and jiggling selective teeth.55 As with normal subjects, category of malocclusion, and degree of mandibular underdevel- however, a broad range of individual activity exists from patient opment at the time of initiation of treatment. to patient. Although openings as large as 12 to 14 mm have been success- Vertical Opening Variations fully treated by clinicians such as Eschler,130 Schwarz,131 Wood- A number of modifications of the original Andresen appliance side and colleagues,81 and Herren95 (Fig. 35-10), two factors favor has been introduced. Many of the modifications are based the reduced opening and incremental sagittal correction. on constructions of different vertical opening requirements Patient acceptance and compliance are significant factors for and different amounts of forward posturing. The question of all removable activators. Daytime use mitigates against bulky whether to posture the mandible in “one great leap forward” or functional appliances that interfere with speech, swallowing, in sequential steps has also given rise to different designs. Petro- eating, and other activities. The wider opening appliances vic and colleagues86 show clear evidence of greater response have a smaller sagittal correction. They have the advantage of with periodic, sequential advancement procedures. Whether depressing the posterior segments if an occlusal cover is used, the appliance is to be worn only at night or full time is another which allows the mandible to move upward and forward if the factor in the design, as is the decision regarding whether the patient has an open bite tendency and reduced interocclusal appliances are to be anchored to the maxilla (as with the Frän- clearance. This result is desirable in open bite problems but not kel functional regulator and the Bionator) or kept loose with in deep bite malocclusions. Histologic evidence also supports minimal wire appurtenances.93 periodic incremental advancement because of the periodically enhanced condylar and fossa response with each adjustment.* * References 46–48, 53, 54, 107, 108. † References 24, 32, 34, 43, 47, 49, 51, 54, 61, 64, 66, 70, 72, 80, 81, 120, 125. * References 32, 35, 42, 43, 84, 118, 132–134. CHAPTER 35 Functional Appliances 997.e57

A B

C D FIGURE 35-11 A, B, Class II, Division 1 malocclusion in an 11-year-old boy with a retained infan- tile swallowing habit. Initial success with the modified Bionator appliance was limited because of the lack of significant growth and patient cooperation. C, D, The patient became motivated after 2 years of intermittent wear, and the results seen were achieved. Pubertal growth acceleration obviously helped. (A and B, Courtesy Erich Fleischer.)

With a single 6- to 7-mm advancement, the condylar and fossa MECHANISMS OF CLASS II CORRECTION WITH growth stimulus is shorter in duration, daytime wear becomes FUNCTIONAL ORTHOPEDICS more difficult, and adverse labial proclination of mandibular incisors may be greater.10,29,93 Again, for a fuller discussion The efficacy of functional appliances no longer needs to of these differences and for design prescriptions for specific be proved, unless one is ignoring many thousands of case malocclusion characteristics, see Dentofacial Orthopedics with reports. Dramatic facial and skeletal changes seldom seen Functional Appliances, 2nd ed., by Graber and associates10 or with conventional fixed appliances are not only possi- Removable Orthodontic Appliances by Graber and Neumann.135 ble but fairly routine (Figs. 35-11 to 35-14). However, the 997.e58 CHAPTER 35 Functional Appliances

10 yr 3 mo 12 yr 9 mo

S-N-A 84° 83°

S-N-B 76° 78°

A-N-B 8° 5°

A to N (perpendicular) 1 mm –1 mm

1 to A +5 mm +2 mm

1 to pogonion +5 mm +6 mm

Pogonion to N (perp) –10 mm –8 mm

Maxillary length 90 mm 91 mm

Mandibular length 107 mm 114 mm

A Skeletal differential 17 mm 23 mm

Saddle angle 125° 127°

Ar to Ptm 31 mm 31 mm

Mandibular plane angle 19° 20°

Anterior face height 68 mm 69 mm

Posterior face height 51 mm 56 mm

Anterior cranial base length 70 mm 71 mm

1 to S-N 110° 102°

1 to Mandibular plane 104° 108°

B FIGURE 35-12 Lateral cephalograms of the patient in Figure 35-11 before treatment (A) and 2½ years later (B). C, Cephalometric measurements. precise reasons that these changes occur are more obscure displacement and remodeling, type of appliance, and patient and vary from patient to patient, as orthopedic surgeons compliance are the most important variables but not the only have observed with their growth guidance procedures in ones.136 Factors such as tissue response and rate of fibroblast long bones. Unfortunately, the overly simplistic attribution turnover are discussed in the superb chapters by Thilander, of the change to condylar growth has clouded the picture Hatch, and Sun (see Chapter 3) and Roberts and Huja (see and is similar to looking at the road as a horse with blind- Chapter 4), all recognized as outstanding authorities. No lon- ers does. Orthodontic practitioners are dealing with a cyber- ger can orthodontists simply estimate the amount of condy- netic process.10 The morphogenetic pattern, growth timing lar change needed to provide the correction. The change is and direction of component parts, neuromuscular patterns, a multifactorial reaction that is too diverse to determine by functional displacement, dentoalveolar compensation, fossa measuring only one component. CHAPTER 35 Functional Appliances 997.e59

Obviously, no reliable method exists for predicting the contribution of each component for the individual patient. Not all functional assessments and physiologic phenomena are reduc- ible to two-dimensional cephalometric tracings with angles and figures or to articulators. Orthodontic practitioners are as precise in their efforts as the best orthopedic surgeons, who would not think of using a cephalometric analysis and an articulator for any joint they treat. The seven components previously listed provide a potential for the needed sagittal change. However, skeletal malocclusions are three dimensional. Weinstein once said, “We are a generation of profiles!” This statement was based on the orthodontic preoccupation with only the lateral cephalogram and an unwillingness to use anteroposterior views to determine equally important transverse characteristics.26,140 FIGURE 35-13 Initial study model depicts a boy, 9 years and 7 Today’s three-dimensional diagnostic procedures provide more months old, who has a severe Class II, Division 1 malocclusion. accurate information. Early functional appliances incorporated (Courtesy Erich Fleischer.) expansion screws or jackscrews to cope with the narrow maxillary arch of most Class II, Division 1 malocclusions (the third As research continues, the fact that nighttime wearing dimension), particularly when the narrowed maxillary arch of appliances largely serves as a transient posturing splint is is caused by abnormal perioral muscle function. Whether by becoming increasingly clear. Telemetric studies, notably those slow or rapid palatal expansion or by fixed or removable appli- of Sander,55 show that function is not enhanced by wearing ances, modern orthodontics recognizes the need to produce a appliances only during sleep. Nevertheless, the forward postur- three-dimensional correction. In no way is this an excuse to ing of the condyle does enhance metabolic action in the TMJ, expand teeth off basal bone, however. Axel Lundström’s epic as shown by Ward and colleagues.80 Increased anabolic and cat- paper116 on the apical base in 1923 is still valid. Some recogni- abolic exchange, not merely forward positioning, may account tion of the need for a three-dimensional therapeutic attack on for enhanced growth of the condyle and posterior fossa wall the problem must be incorporated in the functional appliance, proliferation.4,32,65 or transverse correction can be done before the placement of functional appliances. Nature provides the answer to questions Class II Correction: A Likely Scenario about the amount of expansion that can be achieved when per- The amount of sagittal correction is 6 to 7 mm. The following verted perioral muscle activity is eliminated. In many cases, anticipated growth and adaptational increments (assuming a wearing a functional appliance is likely to eliminate abnormal favorable direction) are typical: and deforming neuromuscular activity without active expan- 1. Condylar growth amount during treatment: 1 to 3 mm— sion adjustments. Too much rapid palatal expansion is being The mandible outgrows the maxilla by 1 to 5 mm, with done without checking the inclination of the buccal segment higher increments predominantly occurring in males. teeth in their relation to basal structures before and after treat- 2. Fossa displacement, growth, and adaptation—Recent re ment. Herein lies a major precipitator of posttreatment relapse. search shows this growth to be 3 to 5 mm, with a dominant vertical vector24 and a positive correlation with the pubertal Bionator growth spurt.* The bulkiness of the activator and its limitation to nighttime 3. Functional retrusion (see Fig. 35-52): This retrusion does wear have deterred clinicians interested in achieving a mixed not always occur in Class II malocclusions and can vary from dentition correction of sagittal discrepancies and eliminating 0.5 to 1.5 mm. Isberg and Isaacson,139 as well as Kantomaa their attendant neuromuscular perversions. The Bionator, as and Pirttiniemi,34 show strikingly reduced TMJ metabolism developed by Balters,141 is the prototype of a less bulky appli- in primates with functionally retruded condyles. Research ance (Fig. 35-15). Its lower portion is narrow, and its upper conducted by Graber,65 as well as that of McNamara41 and portion has only the labial wire and the buccal screening wire Boman and Blume (see Graber118), confirms these observa- extension, plus a stabilizing cross-palatal bar that actually can tions. The controversy results from not knowing the tech- be adjusted for bilateral expansion, if needed. The palate is free nique for a correct determination (see Fig. 35-52).118 for proprioceptive contact by the tongue. The appliance may be 4. More favorable growth direction shown by trabecular orien- worn all the time except for meals, which is critical for maxi- tation: Trabecular orientation changes and can account for mum response. between 0.5 and 1.5 mm. According to Balters,141 the equilibrium between the tongue 5. Withholding of downward and forward maxillary growth117: and the circumoral buccinator mechanism is responsible for Maxillary growth accounts for between 1 and 1.5 mm of the the shape of the arches and intercuspation. This hypothesis sup- change. ports the early form and function concepts of van der Klaauw as 6. Differential upward and forward eruption of lower buccal cited by Graber118 and the later functional matrix hypothesis of segments: Accounts for between 1.5 and 2.5 mm of Class II Moss.142 The purpose of the Bionator is to establish good mus- correction, depending on the depth of overbite. cle coordination and to eliminate potentially deforming growth 7. Headgear effect61,137: Is between 0.0 and 0.5 mm restrictions, while unloading the condyle through a protrusive mandibular position. The upper and lower incisors are usually in contact during wear. Balters attributed a major role to nor- * References 24, 53, 54, 81, 88, 137, 138. mal or abnormal tongue function and posture in deglutitional 997.e60 CHAPTER 35 Functional Appliances

A B

C FIGURE 35-14 Lateral cephalograms and measurements of patient in Figure 35-13. A, Severe overjet is exacerbated by a lower lip trap habit. B, At the end of treatment (patient’s age 13 years and 7 months). C, Patient at age 16 years and 2 months. D, Cephalometric analysis summary. (A–C, Courtesy Erich Fleischer.) CHAPTER 35 Functional Appliances 997.e61

9 yr 7 mo 13 yr 7 mo 16 yr 2 mo

S-N-A 82° 83° 80°

S-N-B 75° 78° 79°

A-N-B 7° 5° 1°

A to N (perpendicular) +3 mm +4 mm +1 mm

1 to A +7 mm +2 mm +6 mm

1 to pogonion 0 mm +5 mm +1 mm

Pogonion to N (perp) –3 mm –1 mm +4 mm

Maxillary length 89 mm 95 mm 92 mm

Mandibular length 107 mm 102 mm 126 mm

Skeletal differential 18 mm 25 mm 34 mm

Saddle angle 130° 128°

Ar to Ptm 34 mm 35 mm 35 mm

Mandibular plane angle 17° 20° 15°

1 to S-N 115° 95° 98°

1 to mandibular plane 99° 103° 98°

Anterior facial height 55 mm 67 mm 70 mm

Posterior facial height 43 mm 49 mm 55 mm

Anterior cranial base length 66 mm 69 mm 72 mm D FIGURE 35-14, cont’d

maturation; Ballard19 later elaborated on this. Research has The function and posture of the cheeks and lips are guided shown that the tongue exerts three to four times as much force by two wire configurations: the palatal bar and the labial bow on the dentition as the circumoral muscles. If the morphoge- with buccal extensions (Fig. 35-17). The palatal bar, which is netic pattern, resting force and viscoelastic properties, tissue made of 1.2-mm hard stainless steel, lies 1 mm away from the rigidity, atmospheric pressure, and intercuspation are included, palatal mucosa and runs distally to a line drawn between the then obviously the dentition and its surrounding structures are distal surfaces of the maxillary first molars. The palatal bar has in a multisystem balance.64,88 a Coffin spring–like configuration. The bar stabilizes and also The standard Bionator (Fig. 35-16) consists of a lower anteriorly orients the tongue to contact the palate. The labial horseshoe-shaped acrylic lingual flange that extends from the and buccal bow is comprised of 0.9-mm stainless steel (Fig. distal of the last erupted molar around to the corresponding 35-18) and does not actually contact the incisors or gingival point on the other side. For the upper arch, the appliance has tissue. The position of the wire produces a negative pressure, only posterior acrylic lingual extensions that cover the molar with the wire supporting lip closure. If necessary, the wire can and premolar regions. The upper and lower parts are inter- be adjusted during the course of treatment, after the arch has occlusally joined in the correct construction bite (protrusive) been widened, to close the spaces and to retract the maxillary relationship. The anterior portion is kept free so as not to incisors. Selective eruption can be achieved during treatment interfere with tongue posture and function. No acrylic cap- by trimming the acrylic. ping of the lower incisors is done, although some clinicians Of all the functional appliances, the Bionator and the Clark choose this variance to attempt to control proclination of the twin block (see Chapter 16) are the most popular. They are lower incisors. less subject to distortion than the efficient Bimler appliance,21 997.e62 CHAPTER 35 Functional Appliances

FIGURE 35-17 Palatal Coffin wire of 1.2-mm hard stainless steel is placed slightly away from the palatal tissue but did not interfere with proprioceptive tongue contact.

CONSTRUCTION BITE Probably the most important aspect of fabrication is the assess- B ment of optimal horizontal and vertical displacement before construction of the appliance. As previously noted, no cookbook FIGURE 35-15 Bionator modified from Balters’ original design. exists for determining the relationships. Much depends on the A, Note the use of a heavy transpalatal Coffin spring instead specific appliance being used, the case selection, the dentofacial of acrylic construction. The large gauge labial and buccal wire morphologic form and structure, the probable growth pattern and is not a tooth-moving appurtenance but a screening wire. To projected increments and direction, and the need for other ther- enhance eruption, the acrylic can be removed in the interdental apeutic assists (e.g., fixed appliances, extraoral force, extractions). area. B, The construction bite is usually taken in an end-to-end The Bionator, originally developed by Balters,10,141 is one incisal relationship, allowing enough room for passage of inter- of the most commonly used removable functional appliances occlusal wires. The appliance is an effective adjunct in many today because of its simplicity, sturdiness, ease of construc- temporomandibular dysfunction problems. tion, ability to be modified, patient acceptance, and use in temporomandibular disorders (TMDs); therefore this section is devoted to a discussion of the construction bite for that type of appliance† (Fig. 35-19). The technique can be adapted to other designs. A complete diagnostic discipline is essential before selecting a functional appliance for a patient.134 As Rakosi and colleagues52,148 emphasize, completing a three-dimensional cephalometric radiographic study and functional analysis for the mixed dentition, use of a functional appliance is no less important than it is for a full, fixed mechanotherapy problem. Facial pattern is important; growth amounts and growth direction are equally important (i.e., growth forecasting, such as developed by the late Dr. Ricketts,124 and computerized digital projection to ensure that the patient is aware of the problem and the projected result [see Chapters 8,9 and 11]). Only if the patient satisfies the demanding functional appliance criteria and only if patient compliance is likely to be good should such an appli- FIGURE 35-16 Basic Bionator appliance. Open palate enhances ance be used. The operator should always keep in mind that tongue proprioception and discourages abnormal growth. Heavy a functional appliance is primarily an interceptive device, sel- buccal and labial wires serve to screen off muscle forces. dom capable of achieving full correction and complete dental detailing. The appliance is a first-phase attack on the total problem. The argument of one-phase versus two-phase treatment which has more wire framework that can be distorted. The suc- will not be settled here. Distinguished proponents ascribe to cessful use of the Bionator in TMJ disturbances has been well both approaches. However, with proper case selection, proper documented10 (see Figs. 35-11 to 35-14). For a fuller discussion wear, and proper patient compliance, the author’s firm convic- of the Bionator philosophy and appliance variations for Class tion, based on thousands of treated cases, good and bad, is that II, Class III, and open bite malocclusions, see Chapter 11 in Dentofacial Orthopedics with Functional Appliances, 2nd ed., by Graber and associates.10 † References 26, 38, 57, 141, 143–147. CHAPTER 35 Functional Appliances 997.e63

FIGURE 35-18 End-to-end construction bite and configuration of 0.9-mm stainless steel labial and buccal screening wire extends to the distal of the second deciduous molars. The wire has no contact with teeth. Fränkel added acrylic to the posterior aspect of the screening wire to make more effective buccal shields.

FIGURE 35-19 Fleischer Bio-Bionator is placed on working models in construction bite relationship. A lower screening wire has been added to prevent a lower lip trap and to allow the tongue to procline lingually malposed lower incisors. This arrangement is similar to the lip shields of the Fränkel function regulator. skeletal and neuromuscular changes can be attained with func- Fig. 35-19). However, the patient’s adjustment to the mandib- tional appliances in first-phase therapy that cannot be dupli- ular protrusion is easier if the advancement is made in 3-mm cated with single-phase treatment. No patents or commercial increments. Evidence exists that this method is more success- ties exist to influence this observation. ful, despite the added work. Usually adjustment can be done In this short survey chapter, the concern is for Class II mal- with a 12- to 16-week interval in the sequential advancement. occlusion, the most frequent challenge and the one with the Procumbency of the lower incisors is less likely with sequen- greatest potential for therapeutic success. For a fuller discussion tial advancement, and patient compliance is better. As Petro- of techniques and appliances and for Class III and open bite vic and colleagues10,86,133 have shown, tissue reaction is also problems, see Chapter 13 in Dentofacial Orthopedics with Func- more favorable, and Rabie and colleagues75,149,150 conclusively tional Appliances, 2nd ed., by Graber and associates.10 demonstrated this on treated cases. Case selection will help determine the decision. Lingually inclined lower incisors, as Anterior Mandibular Posturing with a lower lip trap problem, may respond better with a 5- to In the past, if the sagittal discrepancy was not too great, the for- 6-mm advancement. As a general rule, the anterior advance- ward posturing of the mandible was such that the upper and ment should be 3 mm or more from the most posterior condy- lower incisors contacted in an end-to-end relationship (see lar position in the fossa. Paulsen concurs.73 997.e64 CHAPTER 35 Functional Appliances

A B FIGURE 35-20 Cryogenic primate specimens. A, Control shows normal morphologic and positional relationships of the condyle, disk, eminence, and retrodiskal attachment. B, Significant change is visible in only 6 weeks of wear of a retrusive splint. Dramatic diminution of disk and retrodiskal tissue has occurred. Clearly, forced retrusion has the potential to damage retrodiskal tissue and reduce metabolism, that is, growth and development. (A, Courtesy Isberg; from Gra- ber TM. The unique nature of the temporomandibular joint metabolism; the clinical implications. In: Rabie AM, Urist MR, eds. Bone Formation and Repair. Amsterdam: Elsevier; 1997:143–157.)

A good technique is to have the patient move the mandible Isberg and Isaacson,139 Kantomaa and Pirttiniemi,34 and Pirtti- forward as far as possible and then drop back 3 to 4 mm. If niemi and colleagues,51 as well as the author of this text,65 shows a functional shift to one side or the other occurs because of that retrusive forces on the condyle in the TMJ can impinge on a narrow maxillary arch and convenience swing to one side, the retrodiskal pad, reducing the metabolic exchange and the then lining up the maxillary and mandibular midlines with potential nutrient elements for TMJ and condylar growth (Fig. the construction bite can eliminate this shift. Rakosi, with his 35-20). Definite reduction in the collagen and proteoglycan tremendous experience with functional and fixed appliances content of the condyle shows the effect of reduced anabolic and through the years, has carefully described the construction greater catabolic activity.51 Condylar advancement enhances bite technique, with detailed illustrations and descriptions, to metabolic activity.65 As previously noted, the vertical opening ensure the best possible results, in his chapter in Dentofacial is within the limits of the freeway space. Elevator and protrac- Orthopedics with Functional Appliances, 2nd ed., by Graber tor muscles are activated, and a greater hyoid group compen- and associates.10 sation or retracting force occurs, which is distributed against Because the maxillary incisors are initially and frequently the maxillary arch. This action only slightly inhibits maxillary tipped labially and are often spaced, using an active plate for downward and forward relocation, as studies by McNamara a short period or limited fixed appliances to retract and rotate and colleagues demonstrate39–42,134,151 (see also Chapter 16). maxillary incisors before placing the functional appliance may Biting into the appliance and swallowing enhance the neuro- be preferable to reduce the magnitude of initial mandibular muscular and osseous adaptation (both fossa and condyle) to protraction and to enhance patient compliance. What should the new posture. be made clear is that modern orthodontics is not an either/or therapy. Mixing fixed and functional appliances is easy and Hamilton Expansion Activator often desirable with modern bonding techniques, and func- The Hamilton expansion activator is a variant of the traditional tional appliances are not the “easy and cheap” alternative to monobloc. David Hamilton was often called “the thinking classic full-mouth fixed hardware. Bonding anterior brackets man’s orthodontist.” The first generation of such appliances and placing molar bands on the maxillary arch is a ½-hour time was removable and yet achieved stable correction. Current investment with major returns in better functional appliance bonded appliances reduce the need for patient compliance retention and control of maxillary incisors, rather than resort- and have a high level of success (Figs. 35-21 to 35-24). The ing merely to tipping them lingually with the labial bow of the simultaneous use of two palatal jackscrews permits differential removable appliance. expansion control, which is highly desirable. Too often, a single Despite the controversy that still exists over the idea of the palatal expansion screw does not provide the varying need of existence of posterior condylar displacement in some Class II expansion in anterior and posterior maxillary buccal segments. deep bite malocclusions, seminal research by Dayton Blume The Hamilton philosophy and appliances are described in detail and Vernon Boman demonstrates this phenomenon in selected in Dentofacial Orthopedics with Functional Appliances, 2nd ed., cases. Some patients with TMJ sequelae are relieved only by Graber and associates.10 Hamilton113 points out, as do Gra- by forward posturing of the mandible (see Fig. 35-52, which ber,122 Gianelly and associates,112 and others, that most patients shows research findings of Blume and Boman). This possibil- with these functional appliances need concurrent partial fixed ity should be checked with the diagnostic functional analysis. appliances, transverse correction, or a second period of therapy Tomographic radiographs and scintigraphy, such as that used to complete the required detailing. This fact is vital to ortho- by Paulsen,108 Ruf and Pancherz,53,54 and Pancherz,47 show this dontists’ understanding of the multiple challenges of correcting positional status, taking a postural resting position and maxi- a large variety of malocclusions, depending on a multiplicity of mal occlusion lateral views. However, the astute clinician can causative factors, sexual dimorphism, and when the orthodon- see the same by observation and palpation. Recent research by tist first sees the patient. A B

C FIGURE 35-21 Early version of Hamilton bonded activator (from mandibular aspect). A, The palatal jackscrew is partly open. (Later versions have two palatal expansion screws for more effective localized expansion.) The dark lingual flanges extend toward the viewer. Impressions of the lower posterior teeth are embedded in the occlusal acrylic in the forward postural relationship. B, The Hamilton appliance is bonded to the maxillary arch; again, the lingual flanges vertically extend toward the viewer. C, Lateral view shows the lingual flanges of the bonded appliance. These lingual flanges guide the mandible into its correct anterior construction bite via proprioception.

A B

C D FIGURE 35-22 A, B, Initial facial and profile views show a female patient with a Class II, Divi- sion 1 malocclusion with anterior open bite, no interocclusal clearance, excessive overjet, a con- stricted maxilla, and narrow and retruded mandibular arch. C, D, All of these characteristics cause compensatory and deforming perioral neuromuscular activity. 997.e66 CHAPTER 35 Functional Appliances

E F

Clear acrylic occlusal Plastic expansion screws

.030 Rd. tubes for arch wires

G H I

J K M FIGURE 35-22, cont’d E–H, Posttreatment frontal and lateral facial and intraoral views show significant facial sagittal jaw improvement.I, A twin-screw palatal expansion appliance provides selective buccal segment expansion. This appliance was worn for 8 weeks and was followed by a Hamilton bonded activator (see Figs. 35-21 and 35-23). J–M, Intraoral views of the patient at age 11 years and 6 months indicate that minimum fixed appliance treatment will be required to finish tooth minor alignment and to establish a normal overbite. This is a classic example of a proper two-stage orthopedic appliance management for the twenty-first century. A B

C D FIGURE 35-23 A, B, Molars and incisors are usually bonded, and light arch wire force quickly aligns malposed teeth and corrects any vertical discrepancies. C, D, Buccal tubes have been added on first molars to align the incisors with the bonded brackets.

Dark Corridors

LIP LIP Expansion screw(s) smiling smiling Inter- .030 tube(s) canine for archwires

Inter- Flange length must molar Must fill undercuts exceed the patient's on model but there freeway space and be should be NO relief as long as possible without discomfort C Arch form ??? A Differential expansion: the key to orthopedic alteration of arch form

Taper of Optional hook(s) flanges for elastics Requires Inter- significant Expansion screw(s) canine expansion Double tubes .030 for archwires .045 for facebow Inter- Requires little molar or no expansion B Flange(s) D

FIGURE 35-24 Hamilton dual arch expansion appliance; it can be removable or bonded to the maxillary arch. A, Note the length of the lingual mandibular flanges. One or two expansion screws can be used. Buccal tubes may be added for headgear or arch wire use. B, Drawing shows palatal view with lingual flanges extending toward the viewer. Note the double buccal tubes and twin expansion screws. Lingual extensions guide the mandible forward by proprioceptive contact with mandibular lingual mucosa. A maxillary labial arch may be added, as well as an acrylic cap for the lower incisors. This expansion/functional appliance is similar to the Balters’ Bionator. The maxillary expansion screw void can be filled with acrylic after the desired expansion is achieved.C, Original maxillary narrow arch form is demonstrated with the canine dark corridors highlighted. D, Final arch form is natural. 997.e68 CHAPTER 35 Functional Appliances

Fränkel Appliance deciduous molar embrasure emphasizes the need for this or a Rolf Fränkel93 probably did more to interest American ortho- similar design to maximize withholding the horizontal growth dontists in functional appliances than any single clinician. His of the maxillary arch. The use of buccal shields to screen off outstanding long-term three-dimensional results, the spectac- potentially narrowing muscle forces and of lip pads in the lower ular improvements that have stood the test of time and were labial vestibule to prevent abnormal perioral muscle function done with the highest integrity, showed what can be done with and lingualizing forces makes eminently good sense (see Fig. 138 152 30,121,153 carefully selected patients, properly designed appliances, an 35-25). Enlow and colleagues, Moffett, Graber, 88,134,141 exercise routine (oral gymnastics), and maximal patient com- and others validate the fact that periosteal pull (i.e., vis- pliance. His impeccably researched clinical results are still the coelastic stretch), as created by the Fränkel buccal shields, has gold standard for all functional appliances, fixed and remov- the potential to stimulate bone growth (i.e., expansion of the able106 (Figs. 35-25 and 35-26). Fränkel’s insistence on full-time transverse dimension) and is so well illustrated in cases treated wear and on making the appliance (the functional regulator) with the functional regulator (see Fig. 35-30). Fränkel’s step-by- an exercise device with oral gymnastics during the day demon- step advancement, so easily achieved by the unique appliance strates the significant role of function, per se. His requirement design, has proved to provide the best and most stable results, for anchoring the appliance at the maxillary first molar–second and these results are applicable to other functional appliances.

a b

c d

a B FIGURE 35-25 Fränkel function regulator makes maximum use of the vestibule as an area of operation, screening away abnormal lip and cheek pressures. A, Labial and buccal views. The wire assembly anchors the appliance on the maxillary arch at the mesial first molar embrasure. (a) Labial bow; (b) canine loop; (c) buccal shields; (d) lip pads (pelots). B, No interocclusal acrylic is used, and no interference with eruption of mandibular teeth occurs. A lingual acrylic pad or plate is the only contact with the lower arch, maintaining it in a protrusive relationship in the trough provided by the lingual acrylic pad and the lip pads. Sagittal advancement is usually accomplished in two steps of 3 mm each, with a simple advancement of the posturing trough. Less than full- time wear (except at mealtimes) diminishes the effectiveness of the appliance. (a) Cross-palatal stabilizing wire on the maxillary arch; (b) maxillary looped lingual arch or protrusion bow; (c) lower lingual wires; (d) buccal shield; (e) lip pads; (f) lower lingual pad or plate. CHAPTER 35 Functional Appliances 997.e69

A B C FIGURE 35-26 Fränkel therapy is responsible for this treatment result. A, Beginning study models. B, Autonomous expansion achieved by screening off restrictive muscle activity. C, After 3½ years of treatment, with no retainer control. Note the autonomous arch expansion. (Courtesy Rolf Fränkel.)

Unlike the activator, however, which can be modified in features have been incorporated into modifications of fixed many ways and still produce an acceptable result, the Fränkel functional appliances and activators with beneficial results. appliance demands a rigid discipline of design, fit, and use, However, the popularity of the pure functional regulator as well as proper treatment timing and case selection. Patient has waned, not because of questions about the validity of the daytime wear is a motivational challenge for the orthodontist philosophy, but because of pragmatic use, more demanding and has been an Achilles’ heel in that too many clinicians have laboratory procedures, and compliance demands. (For a full not been able to replicate Fränkel’s spectacular results.154,155 discussion of this approach, see Dentofacial Orthopedics with This failure is partly because of deficiencies in appliance Functional Appliances, 2nd ed., by Graber and associates.10) construction and a lack of experience on the part of the clinician; primarily, however, failure is the result of the lack of Double Plates sufficient compliance on the part of too many patients (i.e., Martin Schwarz131,156 recognized early that a monobloc was bulky full-time wear). Of all the appliances, the functional regulator and difficult to wear. Therefore he introduced the double plate is the one that mostly depends on function, proper fabrica- functional approach. Upper and lower removable appliances tion, sufficient length of wear, and cooperation. Some of its were held in place by wire appurtenances. Opposing occlusal 997.e70 CHAPTER 35 Functional Appliances guiding ramps postured the mandible forward as the jaws were The magnets stimulate repetitive functional activity and TMJ closed. Daytime wear and patient compliance were significantly metabolism and optimize response, similar to the Vardimon improved. The Schwarz plate was the historical precursor of Wil- magnetic appliance discussed later in this chapter.60,158,159 liam Clark’s twin block appliance, which has now become the The orthopedic phase with the twin blocks recognizes the 126 most widely used functional appliance in the world. need for eruption of lower molars to eliminate excessive overbite and deficient vertical dimension. Because the mandibular Clark Twin Block Appliance molars are not covered, they are free to erupt in an upward and The Clark twin block appliance is a modern, highly successful forward vector, aiding in the Class II sagittal correction (see Fig. functional appliance approach modeled after the Schwarz dou- 35-29). Of course, in open bite cases, the molars are covered to 37,44,126,157 ble plate. William Clark has developed this combina- prevent eruption and to close down the bite. tion of upper and lower appliances to a high degree of efficiency. Functional appliances resort to reciprocal Class II dental His book describes all the technical features in detail and shows correction in a noninvasive manner, avoiding the potential iat- 126 many examples of successfully treated cases of all categories. rogenic sequelae of periodontal involvement, gingival inflam- Occlusal guide planes, selective grinding, guided eruption, and mation, crestal bone loss, and root resorption or dilaceration. a midpalatal jackscrew allow for three-dimensional control. This reciprocal upper and lower dental adjustment must be Using wire appurtenances and a jackscrew with the upper and lower inclined planes, the clinician has three-dimensional control (Figs. 35-27 to 35-35). Ease of full-time wear and selective guidance of eruption are attractive features. Similar to Hamilton, McNamara, and others, Clark recognizes the need to restore normal maxillary width and accomplishes this in his active arch development stage of treatment. Some clinicians modify the Clark maxillary component with two expansion screws for differential expansion, similar to Hamilton (see Chapter 16). As with other functional appliances, this modification may also be made ahead of time for transverse deficiencies. The twin block appliances can also be bonded, as with the Hamilton expansion activator. If desired, rare earth magnets in an attraction mode can be incorporated into the guide planes, as Moss142 has done with his functional appliance design.

FIGURE 35-28 Twin block occlusal relief used to expedite eruption of lower molars and reduce overbite.

FIGURE 35-27 Clark twin blocks are modified double plates with occlusal inclined planes. They were introduced by Martin Schwarz to reduce the bulkiness of the traditional monobloc. FIGURE 35-29 In patients with open bites, occlusal cover is The twin blocks meet at approximately 70 degrees, with the maintained over posterior teeth to achieve all possible depres- lower inclined plane mesial in a Class II correction. sion of the upper and lower molars. CHAPTER 35 Functional Appliances 997.e71

FIGURE 35-30 Standard Clark twin blocks. Hash marks denote the occlusal inclined guiding planes. (Courtesy of W. Brudon and J.A. McNamara Jr, University of Michigan. IN Clark WJ: Twin block functional therapy, ed. 2, London, 2002, Elsevier, Ltd)

controlled, of course. Too often, conventional functional appli- are reached. The acrylic is trimmed away from the contiguous ances do not control mandibular incisors, which become exces- maxillary occlusal surfaces to allow for unimpeded molar and sively proclined during treatment. To obtain dental correction premolar eruption. As Buschang and Santos-Pinto24 note, nine with biocompatible measures is not maltreatment, however. times as much vertical growth as sagittal growth occurs in the For example, lower incisors that are initially lingually inclined human face. The lower appliance is usually discontinued unless as the result of a perverted lip trap can be greatly improved. arch length has been gained, and an inclined plane is added to Acrylic capping of lower incisors also reduces the tendency to the maxillary appliance, which serves as an active or short-term procumbency. In any event, Hansen and Pancherz31 note con- retainer for phase II during the continued eruption of poste- siderable recovery from lower incisor proclination after treat- rior teeth as they lock into correct interdigitation. Many studies ment in their long-term studies. emphasize the importance of a locked occlusion to prevent sag- If rare earth magnets are used for phase I of twin block ittal relapse.* therapy, then they are embedded in attraction mode on the 70-degree inclined planes of upper and lower appliances. Func- Magnetic Appliances tional activity and interarch contact are thus enhanced. If the Blechman,163,164 Bondemark and Kurol,165 and Vardimon and appliance is not bonded, then the patient is instructed to wear it colleagues,60,159 as well as Darendelilier and associates166 and all the time, removing it only for cleaning. Moss160 has reported Joho and Darendelilier,167 have been aware of the potential using repelling rare earth magnets in a different configuration, for using rare earth magnets in orthodontics and dentofacial again to assist in forward posturing of the mandible. A thin layer orthopedics for some time. Blechman,168 the true pioneer, has of acrylic covers opposing magnetic surfaces to prevent break- been intimately involved in the medical and dental use of rare ing the parylene seal and thus fostering corrosion. After the earth magnets. Recent medical research corroborates his obser- rapid and desired sagittal correction has been achieved, the twin vations that static magnet fields may have an electric field effect blocks are worn for an additional 2 to 3 months to stabilize the that potentiates tissue response.65,168,169 Despite widespread occlusion and to allow for needed dental compensation (e.g., and increasing use of magnetic adjuncts in general orthopedic posterior eruption, which occurs more slowly). Compensation problems, in vitro orthodontic research has produced mixed is a common problem for all functional appliances because sagittal correction is achieved before vertical treatment objectives * References 20, 31, 37, 44, 47, 53, 54, 57, 60, 159, 161, 162. 997.e72 CHAPTER 35 Functional Appliances

A B

C D

E FIGURE 35-31 Deforming perioral muscle function is noted in an 8-year-old boy before twin block treatment.

results thus far. Is it a question of not knowing what to look Dentofacial Orthopedics the previous year. With the magnetic for? Heightened blood flow is clearly evident, and the align- deimpaction, the tissue attachments and alveolar bone height ment of blood cells is influenced by rare earth magnets, but the are normal rather than the compromised gingival margins magnitude or character of force, its duration, and whether con- observed in conventional expose and pull techniques. No evi- tinuous or intermittent force is applied are questions currently dence of root resorption was seen. being addressed, particularly in medical orthopedics, in which Despite the increased exercise effect of magnets incorporated considerable improvement has been noted in specific types of into functional appliances, which enhances the TMJ–condylar problems, such as back and joint disorders, fracture nonunion, growth metabolism, no compelling evidence currently exists of and pain threshold management. The clinical use of magnets in a significantly enhanced localized tissue effect. This lack of evi- such cases is widespread. dence may be because the magnets are not contiguous to the In orthodontics, Vardimon and colleagues170 have demon- tissues but are separated from them by acrylic barriers. At this strated the clinical use of magnets for the deimpaction of time, magnetic functional appliances do not appear to be much maxillary canines, which can achieve the desired result in as more effective than nonmagnetic designs in a nongrowing child. little as one third of the time required by conventional traction Improper case selection, improper design, and injudicious use technique. The article received the B.F. Dewel Award in 1992 can cause unwanted lower incisor proclination, as with any as the best article in the American Journal of Orthodontics and other functional appliance. Incorporating Fränkel-type buccal CHAPTER 35 Functional Appliances 997.e73

A B

C FIGURE 35-32 The patient in Fig. 35-31 is seen after 14 months of twin block treatment. Note the use of a biteplate during this support phase to stimulate posterior eruption because vertical dimension improvement often takes longer than sagittal correction.

A B

C D FIGURE 35-33 Facial and intraoral views depicts the patient in Figs. 35-31 and 35-32. 997.e74 CHAPTER 35 Functional Appliances

A B

C D FIGURE 35-34 Facial (A, B) and intraoral (C, D) views of the patient in Figs. 35-31 to 35-33 are depicted after a short period of fixed mechanotherapy for detailing.

FIGURE 35-35 Cephalometric tracings of the patient from Figs. 35-31 and 35-32 were created after a 14-month interval. (Courtesy WJ Clark.) CHAPTER 35 Functional Appliances 997.e75

this book, can definitely distalize the maxillary molars and may also have some effect on the maxillary downward and forward growth pattern with possible enhancement of horizontal mandibular growth. Traditionally, despite the mandibular underdevelopment in most Class II malocclusions, American orthodontists have attacked the maxilla with extraoral force, producing a compromise result to fit the maxilla to the deficient mandible. Calling it camouflage treatment does not make it any more legitimate. Because the classic activator is primarily directed against the mandible, what is needed in the best of all worlds is a device that affects a correction using significant changes in both the maxillary and the mandibular basal structures (i.e., growth patterns), plus dentoalveolar compensatory changes. Thus the mechanotherapy must adapt treatment to dentofacial growth in an optimal manner, eliminating three-dimensional malocclusion problems. Normally, the sagittal and vertical growth of the condyles and change in the TMJ glenoid fossa position and morphologic structure are balanced by the downward and forward growth of the maxilla. The great anatomist Harry Sicher attributed the bulk of maxillary basal change to sutural growth.10 As Coben172 emphasizes, however, growth of the sphenooccipital synchondrosis is a significant factor in both a lengthening of the cranial base and the sagittal midface development, as well as influencing the position of the glenoid fossa (Figs. 35-40 to 35-43). This critical area has FIGURE 35-36 Functional magnetic appliance. 1, Lateral view been largely ignored in orthodontic research and diagnosis. with magnets together in a protrusive relationship. 2, Maxillary If the magnitude and nature of the growth processes are appliance with jackscrews for expansion and incisor segment such that the vertical component is dominant, then the man- protraction. 3, Maxillary appliance with expansion jackscrew dibular symphysis will move more vertically. If the horizontal only. Note the guidance prongs in the maxillary appliance. 4, vector is greater, then the chin point will move more sagittally. Mandibular appliance with expansion jackscrew. 5, Mandibu- Functional appliances, alone, actually attack only part of the lar appliance with magnet only (A) embedded in lingual acrylic problem. Korkhaus noted, referring to functional orthopedics, (see Fig. 35-38). A, Miniaturized rare earth magnets coated with “We effect the correction of distoclusion exclusively through 173 parylene to prevent corrosion; B, maxillary forward guidance the mesial development of the entire lower jaw.” However, prong; C, retention clasps; D, labial wire; E, jackscrew. (Cour- is this enough, particularly when definite limitations exist on tesy Andy Vardimon.) the therapeutic change of the mandibular position and morphologic structure? Stöckli and Teuscher persuasively argue in the second and shields or the buccal loops of the Bionator appliance in patients third editions of this text that a combined assault against the with narrow maxillary arches or perverted perioral muscle func- maxilla using a functional appliance and extraoral force produces tion may be beneficial in magnetic and other types of functional a more dramatic and stable correction skeletally, cosmetically, appliances, replacing the jackscrew. The functional appliance, and functionally. Figures 35-41 to 35-44 illustrate the challenges. as with any other mechanism, should be the thinking orthodon- Figure 35-41 shows average natural growth and displacement of tist’s approach and not a procrustean bed or mechanical strait- the maxilla and mandible. The result is harmonious downward jacket for all patients. and forward growth. If mandibular growth is deficient, then a Vardimon and associates have had significant success with more horizontal lower jaw vector must be stimulated to compen- magnetic functional appliances (Figs. 35-36 and 35-37). A sate for the sagittal discrepancy, essentially producing the entire report in the American Journal of Orthodontics and Dentofacial correction with mandibular basal change and stable dental com- Orthopedics highlights the uniform success achieved.76 Two case pensation (see Fig. 35-42). Research shows that solely skeletal reports are shown in Figures 35-38 and 35-39 to demonstrate correction is not possible in many cases with functional or con- Vardimon’s success with magnetic appliances. ventional fixed appliances.174 The orthognathic surgeon recognizes the problem and can effect such a skeletal change through Stöckli-Teuscher Combined Activator-Headgear surgical repositioning or distraction osteogenesis. However, this Orthopedics procedure is beyond the domain of conventional orthodontics Long-term research with even the most efficient removable and this chapter. Figure 35-43 shows the potential of combined functional appliances demonstrates a minimal distalizing effect assault on the maxillary and mandibular sagittal discrepancy. A on the maxillary complex.23,42,100,158,171 A withholding of the more realistic orthopedic possibility is combined maxillary with- anterior component of maxillary change is probably the most holding, plus mandibular and fossa forward displacement, plus that can be expected. Fixed functional appliances such as the vertical control of dental and skeletal spatial relationships. Nei- Pancherz modification of the Herbst appliance, the Jasper ther functional appliances nor extraoral force alone can routinely Jumper, and the De Vincenzo Eureka Spring, all described in 997.e76 CHAPTER 35 Functional Appliances

FIGURE 35-37 Vardimon functional magnetic appliance. Upper and lower modified Schwarz plates, similar to the Clark twin block appliances, are used. Instead of bilateral-angled magnetic inclines, lingual rare earth magnets are buried in the acrylic at the midline. A maxillary guiding prong that slides on the lingual acrylic of the lower appliance during closure brings the mandible forward into the desired protrusive relationship as the attractive magnets contact. This unloads the condyle in much the same way as other functional appliances, except that the functional stimulus occurs more often with the make-and-break magnetic contact. Temporomandibular joint metabolism is enhanced in this manner. Patient compliance is apparently improved. Transverse control can be achieved by incorporating palatal jackscrews if needed. The upper and lower magnets have not been incorporated into the acrylic; rather, they are positioned to show the glide path as they approach each other. Magnetic attraction exists as far as 2 cm (top views). Small elastics hooked above bonded canine brackets to enhance retention of the maxillary functional magnetic appliance (middle view). A, Magnets; B, guidance prong; C, metal tags for incorporation of upper and lower appliances into the acrylic; D, retention clasps; E, elastics hooked over bonded brackets. CHAPTER 35 Functional Appliances 997.e77

A B C

D E

F G

H I FIGURE 35-38 Patient FN was 11 years, 3 months old when functional magnetic system (FMS) treatment was initiated. His Class II malocclusion was due to prognathic maxilla and mild retro gnathic mandible (McNamara analysis: Point A to Nasion Perpendicular line = 4mm, Pogonion to Nasion Perpendicular line = −8mm. Retrognathic mandible according to Steiner analysis: SNA angle = 80 degrees, SNB angle = 72 degrees.) Pretreatment records: A, Profile. B, 3/4 Profile,. C, Overjet. D, Frontal view with excessive overjet; E, Left occlusion. First FMS treatment stage lasted 9 months. A full Class I molar relationship was established, with the canine in almost a Class I relationship, which resulted in overjet remnant. F, Upper FMS appliance. G, Lower FMS appliance. H, I, Increased bite clearance with the FMS. J, End of FMS treatment. K, L, Second edgewise treatment stage: during treatment. M, N, Posttreatment profile and smile.O, Sche- matic illustration provides the percentage correction of each component. Without taking growth into account, major treatment changes occurred in the mandible (75%) and the upper molar (75%). However, after subtracting growth, the mandibular skeletal contribution dropped to 12.3% and the maxillary dental contribution (molar distalization) increased to 92%. OLp, Occlusal line perpendicular. (A–J, Courtesy Abraham Kyriakides. K–N, Courtesy Eleni Dre.)