National Orthodontics Programme Module 15- Treatment Planning British Orthodontic Society 1
National Orthodontics Programme British Orthodontic Society
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About the National Orthodontics Programme
The National Orthodontics Programme was launched in December 2004 following a successful British Orthodontic Society Foundation Award application. A primary aim of the project was to develop a modular learning resource housed in a Virtual Learning Environment for postgraduates in orthodontics (www.ole.bris.ac.uk). This consists of 40 online modules and a series of online assessments. The resource aims to maximize the use of academic staff time and significantly reduce the amount of traveling to teaching bases by Specialist Registrars. The resource has been developed by all UK dental schools as authors or coauthors. It is at the discretion of each dental school as to how the resource is best used in their courses. We hope you enjoy using this unique and pioneering resource.
National Orthodontics Programme Module 15- Treatment Planning British Orthodontic Society 2
Personal Welcome
This Module is intended to outline the structured way in which assessing the data collected should be interpreted to produce an appropriate treatment plan for the individual patient. We shall look at the social and patient factors which might affect the treatment planning process. We will look into those factors identified from the diagnostic data which are important in producing an appropriate treatment plan for the individual patient having identified the aetiology of the malocclusion, the aims and objectives to be produced in treatment including the occlusal and aesthetic outcomes
Learning Outcomes
Candidates should be able to
1. Carefully collect patient information and diagnostic data, and construct a problem list.
2. Thoroughly understand the need for and use of diagnostic investigations and their analysis.
3. Differentiate between problems requiring brief examination of review and problems requiring thorough investigation and planning.
4. List aims of treatment including both features of the malocclusion that could be accepted.
5. Formulate an appropriate treatment plan, including strategy for treatment and retention, therapeutic measures, timing, sequence of their application, prognosis and estimated treatment and retention times.
6. Suggest alternative treatment plans including comprehensive and compromised plans appropriate to the circumstances and be able to discuss the risks and benefits of each.
Objectives
At the end of this module candidates should be able to: • Identify what aspects of the appearance and function of the teeth and face are the source of concern to the patient. • Explain where we would like to place this occlusion both horizontally, vertically and transversely within the face. • Identify those diagnostic features, which we need to identify, to decide how we can determine the best way of satisfying these requirements. • How to plan a structured and systematic method of analysing the collected data and interpreting it to produce a clearly identified stepwise plan for treatment and to identify the risks and benefits of such treatment and the stability of the result. • A list of diagnostic features relating to these aspects is clearly required and also all decisions about how best to assess them. We will also focus on the decision process relating to the need for extractions.
Note that this Module links closely with Modules: 4 (Effect of respiration on facial develop m ent) 14 (Diagnosis) 11 (Cephalometric Analysis) 21 – 25 (Treatment Techniques) 13 (Aetiology)
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Introduction
The treatment planning process is described in the following and you should read the full texts in: • Mitchell M. An introduction to treatment planning, Chapter 1, An introduction to Orthodontics, 2nd edition. Oxford University Press, ISBN 0 19 263184 5. • Sandy J, Harry D, Orthodontics Parts 1-12, Br Dent J 2003. • Proffit WR Contemporary Orthodontics Chapters 6 – 8 3rd Edition. Mosby. • Birnie DJ, Harradine NWT. Excellence in Orthodontics Course. • McDonald F, Ireland A. Diagnosis of the Orthodontic Patient (Chaps 9-10) The principles of treatment planning may be learned in the early part of training. However, to apply these principles for appropriate planning, especially for the more difficult cases, one must have an understanding of treatment techniques and mechanics and the effectiveness and limitations of these various approaches. A knowledge of stability and retention procedures also plays a part in the decision making process. Thus, in many ways, the understanding of treatment planning comes after an understanding of all the other modules rather than first. Your understanding and correct application of your knowledge will therefore evolve over the training. Practical application of the principles over the three-year training period is encouraged, by practice case presentation, with both trainers and your peers. It does begin to make sense towards the end! This module provides notes as an adjunct to aid the understanding of the process but there is no substitute for practical exercises and discussion. The notes within this module should be read in conjunction with the above texts.
Content
1) Treatment planning considerations 2) Effects of treatment on facial and smile aesthetics 3) Notes on Space Analysis and Tooth Size Discrepancy 4) Guidelines for extraction 5) Treatment planning in borderline cases Dentoalveolar - extraction v. non extraction Skeletal - A/P - Vertical - Transverse 6) Treatment of patients with Skeletal disproportion 7) Risk Benefit analysis and informed consent 8) Summary 9) Bibliography
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Section 1 – Basic principles to Treatment Planning Remember that it is not necessary to treat every malocclusion and the benefits to the patient should be carefully assessed prior to undertaking any orthodontic treatment.
Sandy J, Harry D, Orthodontics Parts 1-12, Br Dent J 2003.
Once the aetiology of the malocclusion is understood and the problem list and the aims of treatment established, the treatment plan should consider:
• Oral health. Removal of pathogy, eg caries, must be the primary concern in any treatment plan. • Lower arch • Upper arch • Incisor position and buccal occlusion to be produced • Appliance prescription and mechanics • Retention
Oral health
Lower arch
Plan the lower arch first. The size and form of the lower arch should generally be accepted but consider the aetiology of the malocclusion to determine if any changes in arch form are acceptable. Consider space requirements in 3 planes of space.
Upper arch and the buccal occlusion.
Plan the upper arch around the lower and the incisor and molar relationship to be achieved. As the degree of crowding and overjet increase, then the space and anchorage requirements will also increase and it is more likely that extractions, as opposed to distal movement, will be indicated. The key to achieving a Class 1 incisor relationship is to obtain a Class 1 canine relationship and it is this objective which can help direct you to assessing the space requirements in the upper arch and also give an insight into the difficulties and limitations of treatment. The final molar relationship can then be determined.
Appliance prescription and mechanics
Planning the space requirements and the occlusal movements will lead to the decisions relating to the anchorage requirements and anchorage balance for these movements, appliance design and mechanics required. This plan should then be laid out in a step by step logical progression through treatment to retention. Appliance choices are covered in the modules 21-25.
Retention
See Retention – Module 25
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Section 2 - Facial and smile aesthetics
Ackerman JL, Ackerman MB, Bresinger CM, and Landis JR A Morphometric analysis of the posed smile Clinical Orthodontics and Research :2-11
• Exactly what aspects of the appearance and function of the teeth and face are of concern to the patient. • The relationship between aesthetics and incisor position • Aesthetics of smile – incisor show and smile width / the smile mesh • Aesthetics versus stability • Extractions and facial aesthetics and variability of soft tissue response.
See Module 14 - Diagnostic procedures
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Section 3 – Notes on Space Analysis and Tooth Size Discrepancy
Study Model Analysis in Orthodontic Diagnosis
Kirschen RH, O'Higgins EA, Lee RT. The Royal London Space Planning: An integration of space analysis and treatment planning Parts 1 and 2. Am J Orthod Dentofac Orthop 118: 456-61 • Identify asymmetry within the dental arch (Centre line discrepancy and asymmetric molar relation). • Requires comparison between amount of space available and amount of space required to align teeth properly. • Analysis can be carried out directly on the dental casts or by computer and reflex metrograph.
Calculation of space available:
Measure arch perimeter from one first molar to the other over the contact points of posterior teeth and incisal edge of anteriors.
Segmental approach: divide the dental arch into segments that can be measured as straight line approximations of the arch eg 6-3/ 3 -1/ \1-3 \3-6 or more for greater accuracy. Use dividers and ruler.
Brass wire: contour a piece to line of occlusion then straighten it out for measurement.
Calculation of space required: Measure mesiodistal width of each tooth from contact point to contact point and summate. Sum of widths -- amount of space available = arch perimeter space deficiency (and vice versa)
Combination of Radiograph and Prediction Table Methods
Main problem with using radiographs is distortion of canine, therefore could use size of incisors from Study models and size of unerupted premolars using films to predict size of unerupted canines. A graph developed by Staley and Kerber from Iowa growth study data allows canine width to be read directly from the sum of the incisor and premolar widths. This method can only be used for the lower arch and requires periapical radiographs. For white children, it is quite accurate. For white, Northern European children the Staley - Kerber method will give the best prediction, followed by the Tanaka - Johnston and Moyers approaches. These methods are superior to measurement from radiographs. The Tanaka - Johnston method is the most practical and simple. For Black / Oriental patients direct measurement from radiographs is best approach. If obvious anomalies in tooth size or form are seen in the radiographs, the correlation methods (which assume normal tooth size relationships) should not be used.
Tooth Size Analysis
For good occlusion, the teeth must be proportional in size. Approximately 5% of the population have some degree of disproportion among the sizes of individual teeth, known as tooth size discrepancy. An anomaly in the size of the lateral incisor is most common. Tooth size analysis / Bolton analysis is carried out by measuring the mesiodistal width of each permanent tooth. A standard table (eg Proffit p. 170) is then used to compare the summed widths of the maxillary and mandibular anterior teeth and the total width of all upper to lower teeth (excluding 7's and 8's)
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A quick check for anterior tooth size discrepancy can be done by comparing the size of the upper and lower incisors (upper 2's should be larger than the lowers). A quick check for posterior tooth size discrepancy is to compare the size of upper and lower 5's which should be about equal size. A tooth size discrepancy of < 1.5mm is rarely significant. Assumptions:
1. AP position of incisors is correct (retrusion accentuates crowding & protrusion alleviates crowding) 2. Space available will not change because of growth (class II, class III, long face, short face)
See Module 14 - Diagnostic procedures for Mixed dentition space analysis.
Estimation of the size of unerupted teeth Measurement from radiograph requires an undistorted image, more likely with individual periapicals than an OPG. There is a need to compensate for magnification by measuring an object that can be seen both in the radiograph and on the SMs eg 1 ° molar: True width of 1 ° molar = True width of U/E premolar Apparent width 1 ° molar Apparent width WE premolar The technique can be used in both arches for all ethnic groups
Estimation from Proportionality Tables A reasonably good correlation between size of erupted permanent incisors and size of unerupted canines and premolars has been tabulated for white American children by Moyers (Proffit p.168). Mesiodistal width of lower incisors measured and is used to predict size of both upper and lower canines and premolars. Size of lower incisors correlates better than size of upper incisors as the upper lateral incisor is a very variable tooth. However, there is a Tendency to over-estimate size of unerupted tooth with this method, but it is fairly accurate and no radiographs are required.
Tanaka and Johnston prediction values:
Tanaka MM and Johnston LE J. Am. Dent. Assoc. (1974) 88:798
One half of the mesiodistal width of the four lower incisors + 10.5mm = estimated width of lower 3, 4 and 5 in one quadrant
One half of the mesiodistal width of the four lower incisors + 11.0mm = estimated width of upper 3, 4 and 5 in one quadrant This method has good accuracy but a small bias towards overestimation of tooth size. No radiographs or tables required are required.
The clinical application of a tooth-size analysis It is stressed, once again, that the analysis should be regarded as a useful guide and not as some utopian vision that anchorage, growth, mechanics and patient compliance can be controlled with total accuracy.
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Bolton WA. The clinical application of a tooth size analysis. Am J Orthod 1962; 48: 504-29.
If the overall ratio > 91.3% the mandibular teeth are too wide compared to the maxillary teeth. The main cause of tooth width discrepancy is a right-left asymmetry of mesiodistal tooth size. If the anterior ratio is greater than 77.2% the total width of the lower six anterior teeth is relatively too large. If it is reduced the discrepancy is due to an excess in maxillary tooth material. Bolton also produced some tables. Once the Bolton ratio is calculated and the arch with the relatively smaller tooth material determined, you can locate the actual figure corresponding to the arch tooth size on the table. The ideal value for the size of the opposing teeth is read off the accompanying column. The difference between the actual value and the ideal represents, in mm, the amount of excess tooth size in this arch.
Johal AS, Battage JM. Dental Arch crowding: A comparison of three methods of assessment. Eur J Orthod 1997; 19: 543-551.
All methods are prone to error (landmark identification, individual interpretation, validity, proper archform hence perimeter length. The Reflex microscope is not intended for clinical use (expensive, time consuming, difficult also to assess tilted teeth as casts are clamped). The visual technique is easy but due to space being assessed in a straight line (ruler), this may explain why crowding is overestimated. Brasswire method tends to underestimate crowding as it could be that a ruler (sensitivity of 0.5mm) may underestimate tooth width.
Irregularity index (Little) Calculates the sum of the distances between the tooth contact points measured in parallel with the occlusal plane (reflects linguo/labioversion, displacement, and rotation). In proper occlusion the anatomic contact points of adjacent teeth should abut one another. Can range from zero (perfect alignment) to large upper limits. It is however insensitive to reciprocal rotations of adjacent teeth.
Conclusions There is a modest correlation between these two methods because they provide complimentary information. The Space Analysis is more attuned to tooth displacements while the Irregularity index is susceptible to axiversions. The irregularity index is a measure of irregularity alone. It is not affected by divergent axial inclinations or where teeth are displaced but do not overlap.
Selwyn-Barnett BJ. Rational of treatment for Class 11 Division 2 malocclusion. Br J Orthod 1991; 18: 173-181.
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Non-extraction may enable easier and more successful treatment of Class II/2 cases. This method may not push the teeth out of the position of soft tissue balance. Extractions do not guarantee stability (Little) so some lower incisor crowding following this non extraction approach is acceptable. Mild crowding does not justify premolar. However prolonged/ permanent retention should be considered. It's OK when appropriate!
Braun et. al. The Curve of Spee revisited. Am J Orthod Dentofac Orthop 1996; 110: 206-210. The result of this investigation suggests that the difference in arch circumference before and after leveling is less that was found by others (eg. Germane, Garcia) As an example, a curve of Spee depth of 9mm would only increase the circumference by 2.04mm after leveling. This would be associated with an incisor proclination of 3.2° (if canine width is kept constant).
This is less than that found clinically using continuous archwires and suggests that some proclination is due to the mechanics, such as inserting a reverse curve into the wire.
The authors suggest using segmental archwires (such as Burstone's intrusion arch) to selectively intrude the incisors or to extrude the premolars and molars. This may prevent unwanted excessive incisor proclination.
Germane N et al. Arch Length Considerations due to the Curve of Spee: A Mathematical Model. Am J Orthod Dentofac Orthop 1992; 102: 251-255.
It was long assumed that I mm of arch circumference is needed to level each millimetre of Curve of Spee. Previous workers such as Baldridge and Garcia found however that less than l mm of arch circumference was required to level the curve. This study was to produce a mathematical model to quantify this. A Catenary curve is narrower in the canine and second molar regions than a Bonwill-Hawley archform. Therefore, for a given curve of Spee, the arch circumferences measured at either the first or second molars are longer for the Catenary curve than the Bonwill-Hawley archform. This implies the type of archform has a clinical impact on the amount of arch circumference.
Previously Baldridge and, separately, Garcia found a linear relationship ( less than 1 to 1 ) between arch circumference/perimeter and curve of Spee but re-examination of the statistics used showed flawed analysis and so a linear relationship could not be assumed. This nonlinear relationship is confirmed by this present mathematical analysis. For the catenary curve the amount of arch circumference required for levelling is consistently less than one to one for curves 10mm or less for the Bonwill-Hawley archform. The amount of arch circumference was less than 1:1 for all curves of 10mm or less when the arch circumference was measured at the first molars. The amount was also less than 1:1 for curves less than 9mm when arch circumference was measured at the second molars. Yet the arch circumference required was more than 1:1 for curves of Spee or 10mm when the arch circumference was measured at the second molars using the Bonwill-Hawley archform. Therefore, in Bonwill-Hawley archforms the amount of arch circumference required for levelling the curve of Spee varies depending upon depth of curve and from where the arch circumference is measured. Most preformed archwires at present are based on a catenary curve.
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Section 4 - Summary guidelines for the extraction of teeth
Assessing the lower arch crowding
Category mms of crowding Extraction pattern Consider: Mild 1 to 4mm Non extraction or second premolars
Moderate 5 to 8 mm First premolars or second premolars
Severe 9+ mm First premolars
The choice of teeth for extraction for orthodontic purposes is dependant on the following factors:
General Factors
• Gross pathology, eg. caries, periodontal conditions, hypoplasia • Gross Displacement • Abnormal morphology.
Factors specific to the malocclusion
• Patients dental and facial aesthetics and profile. • The A-P skeletal pattern • The vertical skeletal pattern. • The transverse relationship of the arches. • Soft tissue factors, eg. Large flaccid tongue and lips etc. • The degree of crowding.
• Site of crowding • Whether it is an orthodontic or surgical treatment plan. • The need for antero posterior movement of the teeth relative to the skeletal base for orthodontic camouflage e.g. the reduction of an increased overjet. • Space for flattening the curve of Spee and reduction of the overbite. • Space for centreline correction. • Space needed for correction of the molar relationship. • The anchorage requirements of the proposed tooth movements. o i) Tip and torque adjustments planned for the incisors o ii)The inclination of the canines.
• Anchorage requirements and anchorage balance • Age of patient - more difficult to close space in older pts.
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Section 5 - Treatment of Borderline Extraction / non extraction Cases Extraction pattern in mild / moderate crowding problems
• Contemporary guidelines for orthodontic extraction in Class I crowding and / or protrusion (Proffit). • Less than 4mm arch length discrepancy: extraction rarely indicated. • Arch length discrepancy 5 to 9mm: non-extraction or extraction treatment possible. The extraction/non-extraction decision depends on both the hard- and soft-tissue characteristics of the patient and on how the final position of the incisors will be controlled. Non-extraction treatment usually requires transverse expansion by uprighting across the molars and premolars. • Arch length discrepancy 10 mm or more: extractions always required.
First premolars If the crowding is mild, extraction of first premolars may result in residual spacing. The loss of first premolars is recommended for moderate to severe crowding, especially to allow buccally placed and crowded canines to erupt. If fixed appliances are the used to close the remaining space, there is a danger of overretracting the labial segment, which may have deleterious effects upon the profile. Consider extracting teeth further distal in the arch.
Second premolars
• Congenital absence of second premolars and crowding of the arch • Hypoplasia of the second premolars and crowding of the arch • Severe displacement of the second premolar • Mild to moderate crowding (2-4mm per quadrant) • Where space closure by forward movement of the molars rather than retraction of the labial • segments is indicated whilst taking into account the molar relationship.
Second permanent molars Indications: • Facilitation of distal movement of the upper buccal segments. • Correction of moderate Class II malocclusion in mature adolescents with limited growth potential. • Do not expect more than 4mm distal movement. • Ideal patient with less than full cusp Class II molar relationship. • Relief of mild lower premolar crowding (1-2mm of space in premolar region). • Provision of additional space for the third molars and thus reduction of the likelihood of their impaction. • Prevention of lower labial segment crowding.
Expansion
Before deciding whether arch expansion is appropriate, the aetiology of the individual arch form needs to be identified. The method of expansion can then be determined. However, of expansion in the intermolar region may not provide more than one half to one third within the arch.
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Distal movement of molars Indications in the upper arch:
• Class I with mild upper arch crowding, or mild II division 1 with a well aligned lower arch and molar relationship less than half a unit Class II. • When extraction of both upper first premolars does not give a sufficient space to complete alignment and/or overjet reduction in the upper arch. • Where early unilateral loss of a deciduous molar had resulted in mesial drift of the first permanent molar. • Where upper arch is crowded but a median diastema is present.
Enamel interproximal reduction Interproximal enamel reduction (stripping) can be effectively used to gain space in the upper and lower arches and also to coordinate tooth sizes between the two arches. Each tooth has 0.75 to 1.25 mm of interproximal enamel surface
It is safe to remove 0.25mm of enamel from the contact areas of these teeth
In theory, 22 tooth surfaces available from mesial of the first molar on one side to the other, a total of 5.5mm of space can be gained. However, in practice, interproximal reduction is usually performed on upper and lower incisors only.
Section 6 - Treatment of Patients with Skeletal disproportion There are three possible approaches: 1. Functional Appliance therapy (Growth modification).
2. Camouflage of the skeletal jaw discrepancy by orthodontic tooth movement. Extractions are usually necessary to allow movement of the teeth relative to the skeletal base in an effort to camouflage the skeletal discrepancy. The dental occlusion is corrected but the skeletal discrepancy remains.
3. Combined orthodontic and orthognathic surgical treatment. This involves surgical correction of the jaw discrepancy in combination with orthodontic treatment to position the dentition to produce optimal facial aesthetics and occlusion.
Considerations for each of the possible approaches
Functional Appliance (Growth Modification)
See Module 22
The ideal patient for functional appliance treatment
i) Class II division I malocclusion in patients with excellent remaining growth potential. ii) Non-extraction due to well aligned arches. iii) Skeletal mandibular retrusion. iv) MM angle average or reduced with an increased overbite. v) Maxillary incisors proclined.
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vi) Mandibular incisors retroclined. vii) Class 111 malocclusion eg Frankel 111, face mask or reverse twin blocks although with limited success.
Camouflage Orthodontic Treatment
• Consider the camouflage of the A-P, Vertical and Transverse skeletal discrepancies.
• With extraction of teeth it is possible to obtain correct molar and incisor relationships despite an under-lying Class 2 or Class 3 skeletal relationship.
• Considerable retraction of the upper incisors can be accomplished for most patients before problems are encountered with the following: • A relatively prominent appearance of the nose. • An unaesthetically obtuse nasolabial angle. • A lack of palatal bone into which to retract the upper incisors. This can be judged on the pre- treatment ceph by judging the degree of retraction necessary to achieve the correct lower incisor edge to upper incisor root centroid relationship. • The functional orthodontists would claim that over-retraction of the upper incisor teeth in camouflage cases limits the functional movement of the lower jaw and causes temporomandibular joint dysfunction. There is however a lack of convincing evidence in the literature to support this idea.
• Proclination of the lower incisors may result in the loss of labial bony support and labial gingival recession. In the more severe Class 2 patients it may be possible to obtain a good dental occlusion only at considerable expense of facial aesthetics. The upper incisors must be displaced a long way distally to compensate for a retrognathic mandible. The aesthetic result in these cases is increased prominence of the nose and an overall appearance of lower facial deficiency with an obtuse nasolabial angle.
• Ironically improvements in orthodontic mechanics that allow for greater displacement of the teeth have made it possible to obtain occlusal correction in Class 2 patients that go beyond the limits of successful camouflage from an aesthetic point of view.
Camouflage for the Class 2 patient:
In this line of treatment the extraction spaces are used to produce dental compensation, and extractions are planned accordingly. For example a Class 2 patient with a mild to moderate mandibular deficiency: i) Both upper first premolars are removed to allow retraction of the maxillary anterior teeth and non extraction in the lower arch to produce a class 11 molar relationship. ii) Extraction of the teeth in the lower arch is planned to create space for levelling and alignment. iii) If extractions are necessary generally lower second premolars are chosen in an effort to avoid retroclining the lower labial segment and working against the orthodontic camouflage and changing the anchorage balance during space closure. iv) Class II elastics are helpful.
Camouflage for Class 3 Patients Camouflage with Class 3 patients is generally less successful than in Class 2 patients. Excessive retraction of the lower incisors makes the chin more prominent, and even minimal retraction often magnifies the facial aesthetic problems associated with Class 3 skeletal malocclusions. Camouflage is therefore only suitable for mild Class 3 skeletal problems and certainly is much more successful in Class 2 patients.
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It is important to note that extraction of teeth provides space for the displacement of teeth only in the AP plane of space. Therefore in the patient who also has a vertical or transverse skeletal problem the extraction of teeth for camouflage will not address the problems in these planes of space. However, i) In the lower arch lower first premolars are often extracted to allow retroclination of the lower incisors. ii) In the upper arch the patient would be treated either non-extraction or with the extraction of upper second premolars to avoid retroclination of the upper incisors which would work against the Class 3 camouflage. iii) Class III elastics are useful. However, space requirements in both arches, incisor position and planned movements together with anchorage balance considerations must be taken into account rather than the simple application of a predetermined formula for the extractions required.
Considerations of Age, Growth and Treatment Limitations
Class I skeletal base
In the A-P assessment of class 1 skeletal base, there is obviously no concern with the skeletal base assessment as the jaws are in a `normal' relationship. The following points are of importance in the case of a borderline extraction/ nonextraction case, in assessment of the A-P position of the soft tissues and incisor teeth.
Soft tissue profile
The lips should be assessed clinically for protrusion (e.g. fleshy everted lips as in cases of bimaxillary protrusion) or retrusion, with thin lips together with mentalis activity. Lip competence should also be evaluated.
Dentoalveolar assessment
The degree of crowding and incisor protrusion must be considered together with the soft tissue assessment above. As well as clinical assessment, the study models and lateral ceph can be referred to. The APog line can be used as an aesthetic guide for the lower incisor position. Raleigh Williams (1969) claimed that the lower incisor edges should be at or near the APog line for optimum aesthetics and stability. Houston and Edler (1990) however, found that the APog line was not a position of stability. If there is a borderline amount of crowding, e.g. 4 - 5mm, the decision may be made to extract if it was felt that the profile would become too protrusive with a non extraction treatment plan, or conversely not to extract if it would become too retrusive. It may even be the case that if no crowding exists, but the lips were incompetent and the profile unacceptably protrusive, that the decision to extract is made. It must be kept in mind however, that the the A-P position of the lower labial segment should not generally be altered (Mills 1968) with some exceptions to the rule. However, one might compromise aesthetics for stability and vice versa.
Class 2 skeletal base
The borderline treatment decisions for class 2 cases fall into those between: Functional / camouflage and Camouflage / surgery. The following considerations should be taken into account in the A-P assessment.
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Skeletal base
The patients' skeletal base should be assessed with the patient in the natural head posture. It must be established where in the facial skeleton the problem lies (i.e. prominent maxilla, or retrognathic mandible) and the severity of the relationship ( mild, moderate or severe) The lateral ceph can be referred to for confirmation of the clinical findings, by looking at the ANB angle and the Wits analysis
Soft Tissues
The soft tissue profile must be examined as for the class I cases, examining the lips for competence and prominence etc. The extent to which the soft tissues camouflage the underlying skeletal pattern should also be evaluated. The prominence of the nose and chin are important to assess, as is the naso-labial angle and chin-throat length. Dentoalveolar
• The degree of crowding and dental protrusion should be evaluated. • The angulation of the incisors i.e. proclined or upright should be determined. • The amount of bone available palatal to the incisor teeth should be assessed on the ceph, as this may identify a limiting factor for camouflage treatment. • The A-P relationship of the molars and canines should be identified as these will help in determining anchorage requirements.
Functional appliance therapy (Growth Modification) Obviously age plays a significant consideration in this decision, in that once past the pubertal growth spurt, growth modification would not be the treatment of choice. If however the child still has good growth potential, the decision may not be so easy. The following, are points to consider when planning treatment;
1. If the profile is retrognathic, the patient may have more benefit from a functional appliance rather than camouflage, even with the use of headgear (a type of growth modification itself). Research by Tulloch has shown that although both headgear and functional appliances restrain maxillary growth and encourage mandibular growth, those that had headgear had approx. 1mm more maxillary restraint and those that had a functional appliance had approx. 2mm more mandibular growth. 2. Soft tissue profile- if the patient has a prominent nose and chin, obtuse naso-labial angle or thin lips, it may be beneficial to err on the side of caution when deciding whether or not to extract (as discussed above). Treatment with a functional appliance initially, may eliminate the need for subsequent extractions, as anchorage is gained during this phase of treatment. Research by Paquette Beattie and Johnston (1992) demonstrated that in borderline II/1 cases, the non extraction cases where 2mm `fuller' than the extraction cases.
3. In a case with upright upper incisors, or already fairly proclined lower incisors, functional appliances may need to be avoided, as the functional appliance would encourage further tipping of the incisors in an unfavourable direction. 4. In cases where the anchorage requirement is high e.g. the molar relationship is a full unit II, functional appliances can be beneficial.
5. If the patient will obviously need extractions to resolve other problems, it may be prudent not to go for a two phase treatment as this may prolong the treatment plan.
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Camouflage/ surgery The patients in this category will be older adolescents or adults, where there is little or no growth potential. Obviously the more severe skeletal patterns will make successful camouflage more difficult as either the tooth movements are not possible (due to lack of alveolar bone to move the teeth into) or a compromise of facial aesthetics. It may be possible to get the teeth into a good occlusion, but at the expense of the facial profile. In these cases a combined approach to treatment should be considered A thorough assessment of the effects of any planned tooth movements on the soft tissues should be made.
In these borderline cases it may not be possible to achieve both occlusal and aesthetic goals and a compromise may have to be reached.
Refer to the following for very useful information on considerations in the treatment of borderline cases:
Proffit WR Contemporary Orthodontics 3rd Edition Chapter 8. Pub. Mosby. Page 282 Fig 8-46.
This contains guidelines proposed by Proffit to identify the limits of Skeletal relationships in Class 2 beyond which camouflage would not be successful.
Class 3 Skeletal base
The borderline treatment decisions for patients with a class 3 skeletal base are between those of Camouflage (+/- functional appliance therapy) and orthognathic surgery with orthodontic treatment.
Skeletal assessment
The severity of the skeletal base discrepancy should be determined, as well as identifying where in the facial skeleton the problem lies, i.e. is it the mandible that is too prognathic or the maxilla that is too retrusive? See Arnett and Bergman (1994).
The cephalometric assessment can help to indicate the severity of the skeletal base discrepancy. Soft tissue assessment
As before.
Dentoalveolar assessment
The degree of crowding, and incisor protrusion are again important, in particular the extent to which dentoalveolar compensation has occurred. The patient should be examined clinically for any anterior displacement, which may be present if teeth are in x-bite, as this can give an exaggerated appearance to the malocclusion. The patient should be examined to see if they can achieve an edge to edge relationship.
Camouflage/ Surgery
This borderline is reached sooner in Class 3 cases than class 2 cases.
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The facial profile is often exaggerated by camouflaging the malocclusion, as the lower incisors are retracted the chin becomes more prominent. Approximate values for the amount of proclination and retroclination of the upper and lower incisors respectively that can be achieved in order to camouflage a class III malocclusion are 1200 and 800
The ANB difference should be used as a guide. Kerr suggests that an ANB difference of greater than – 40 would indicate the need for surgery. (others suggest that – 20 is more realistic). (Kerr, 1994).
Clinically, if the patient can achieve an edge to edge relationship, this would indicate that camouflage maybe possible. As with class 2 cases, the effect of camouflage of the facial profile must be assessed. If this is likely to cause aesthetic problems, a combined approach should be considered. When Skeletal Discrepancy outside the limits of Orthodontic camouflage treatment alone. The characteristics of a surgical case are 1. Severe Skeletal discrepancy .or dental alveolar problem. 2. Adult patient 3. Younger (post pubertal) with severe or progressive deformity. 4.Good medical and dental health.
Some degree of dental compensation accompanies most skeletal jaw discrepancy. If they are to reposition surgically this dental compensation must be removed. The borderline case orthodontic /surgical is common for adolescent Skeletal 2 cases. No RCTs exist and probably never will! Some data does give some guidance: Post growth with >10mm OJ, short mandible, proclined lower incisors and or long face, would indicate a problem too great for camouflage.
Augmentation genioplasty may be considered as an adjunct to Class 3 camouflage but the risk of severe resorption of upper incisors increases 20 fold when the lingual plate is contacted when torquing upper incisors back during Class 3 camouflage and tipping them labially in Class 3.
Failed camouflage with resorbed roots may undermine retreatment with surgery. Lower labial segment moved 2mm forward is unstable unless severely retroclined initially. Likely to occur in Class 3 camouflage when Class 111 elastics used unless lower premolars ext.
Borderline Vertical Discrepancies
Borderline vertical discrepancies often present diagnostic dilemmas. Treatment planning is complicated by the fact that vertical mandibular growth continues well into adulthood and perhaps indefinitely. Determining whether future growth will follow an anterior or posterior pattern of rotation can also be difficult and unpredictable. Vertical growth is generally beneficial in deep bite malocclusions but in high angle cases worsens the prognosis. To treat or not to treat?
Patients do not generally complain about an increase in overbite, or a reduced overbite, but it is obviously an aim of comprehensive orthodontic treatment to correct a vertical discrepancy. If the malocclusion is mild and aesthetically acceptable to the patient, it may be wise not to embark on treatment. An increased overbite treated with the preadjusted edgewise appliance will require a long course of treatment and the benefit to the patient may be small. If the overbite is reduced, an AOB can develop or worsen significantly due to the extrusive nature of orthodontic forces and, again, is probably best untreated particularly with the unpredictable nature of late mandibular growth.
Camouflage / Functional Appliance therapy Whether a particular malocclusion is tackled by orthodontic camouflage or functional appliance therapy (growth modification) is usually a question of the patient's age and AP discrepancy.
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Deep bite malocclusions are particularly amenable to growth modification and treatment can be initiated early in the pre-pubertal phase with functional appliances and anterior bite planes. High angle cases must be handled more carefully with modifications such as high pull headgear, buccal bite blocks, chin caps, microscrew implants etc. Since orthodontic mechanotherapy is extrusive in nature, camouflage treatment is more suited to correction of deep bite malocclusion than open bite tendencies. Also, because vertical growth continues into late adolescence, correction of increased overbite can be attempted beyond the pubertal growth spurt when there is a degree of useful vertical growth remaining. Relative intrusion of the lower incisors (molar extrusion) is therefore accompanied by growth in posterior face height, which prevents excessive steepening of the mandibular plane. In "non-growing" adults however, an overbite must be corrected by true intrusion of the lower incisors, which is limited in amount, as molar extrusion is probably unstable.
Camouflage in high angle cases is more challenging as intrusion of the buccal segments is practically unattainable and extrusion of the labial segments is unaesthetic and unstable. Often, the treatment is best delayed until late adolescence when the effect of remaining growth on the occlusion can be discerned. If camouflage is attempted, extrusive orthodontic forces must be carefully controlled to avoid exacerbating the downward and backward rotation of the mandible, which worsens both AP and vertical relationships. Borderline extraction decision In a low angle patient with increased overbite, premolar extractions should be avoided since retraction of the lower labial segment will worsen the overbite and also because excess space is difficult to close due to the patient's strong musculature. Instead, arch lengthening, a small amount of arch expansion or extraction of second molars should be considered in preference. In high angle cases, anchorage can be lost rapidly and space can be closed with relative ease, therefore where space requirements are borderline, it is better to extract.
Borderline Orthognathic Cases At best our assessment of what can be achieved orthodontically is semi-quantitative; there are guidelines, but no strict cut off points to determine whether correction is feasible by orthodontic means alone or whether an orthognathic approach is indicated. Proffit describes an "envelope of discrepancy" to judge whether the severity of the malocclusion is within the limits of orthodontic correction or growth modification alone. The decision is based on the patient's concerns as much as the operator's boundary for orthodontic correction. Even if is possible to correct the occlusion by orthodontic camouflage; the facial profile and aesthetics may override the decision. This is more likely to apply to long face malocclusions and VME, as patients are less likely to seek treatment for a short face discrepancy. Obviously, the age of the patient is all important and a deep overbite that may be correctable with orthodontics in an adolescent will require surgery in an adult. Other patient related factors must also be taken into consideration such as a wish to avoid surgery at all costs, or a medical history that contraindicates or complicates orthognathic surgery. The vertical relationship cannot be assessed in isolation and if superimposed on a skeletal discrepancy in another dimension the complexity of the case is obviously increased and possibilities for camouflage reduced.
Borderline transverse skeletal discrepancies Transverse discrepancy is defined as a discrepancy in the buccolingual relationship of upper and lower teeth or maxilla to mandible.
Transverse discrepancy of the teeth is commonly known as posterior crossbite and can affect primary and secondary dentition. The prevalence of posterior crossbite in all dentitions seem to vary between 8 - 19% with predominance for unilateral crossbite (Foster and Hamilton 1969; Day and Foster 1971). Leighton claimed that crossbite should not be routinely treated in primary dentition because of the high rate of spontaneous correction (1966).
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Treatment planning
Depending on the severity and age of the patient at presentation
Options include: • Primary dentition - removal of premature contact especially C's in children • Extraction / Non extraction to include asymmetric extractions to correct dental asymmetry • URA with midline screw and posterior capping • Quad helix • Rapid Maxillary Expansion (RME) for children before fusion of mid-palatal suture • Surgically assisted RME for adults • Functional appliances • Head gear • Fixed appliances to include asymmetric torque • Joint orthodontic / orthognathic surgery • Orthognathic surgery • Distraction osteogenesis • Joint orthodontic / restorative dentistry • For soft tissue discrepancy bone grafts and implants may be considered • Consider bracket prescription and placement
Summary: Characteristics of the Patient for Camouflage Treatment i) Too old for successful growth modification. ii) Mild to moderate Class 2 skeletal relationship or mild Class 3 skeletal jaw relationship. iii) Reasonably good alignment of the teeth so there is space available for AP correction, as not all of the space created by the extraction is used for the alignment of crowded teeth. iv) Acceptable vertical proportions, neither extremely low angle (deep bite) or extremely high angle (anterior open-bite tendency).
Camouflage should be avoided in the following situations i) Severe Class 2 or Class 3 skeletal discrepancy and patients with a significant vertical skeletal discrepancy. ii) Patients with severe crowding and protrusion of the incisors in which all the extraction space will be required to achieve alignment of the incisors and none will be available for AP displacement of the incisors. iii) Patients with excellent remaining growth potential who, perhaps, would be most appropriately managed with growth modification. iv) Non-growing adults with more than a mild or moderate skeletal discrepancy, who perhaps would best be managed with orthognathic surgery.
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Borderline Patients - Possibilities and Limitations
One of the most difficult decisions facing the clinician is whether the patient with a borderline skeletal discrepancy can be successfully treated by orthodontics alone. The decision must be made from the very beginning as the orthodontic preparation for surgery differs significantly from the orthodontic treatment for camouflage. Ill advised attempts to camouflage problems that are too severe extend treatment time and compromise the final result, on the other hand, unnecessary surgery should be avoided. The problem facing clinicians therefore, is how to decided which patients have the potential to be successfully camouflaged, and which are better surgical candidates. Factors that are helpful in making this decision are as follows: General Factors
i) The patient's health status - are they a good risk for surgery and a general anaesthetic from a health point of view?
ii) The specific nature of the patient's complaint - is it related to the appearance of the dentition or the appearance of the face?
iii) The patient's view of the acceptability of the surgical treatment plan.
Factors Specific to the Malocclusion
Facial Aesthetics - when considering the prominence of the nose and the obtuseness of the nasolabial angle, the clinician needs to ask the question; will retraction of the upper incisors achieve a good dental occlusion at the expense of facial aesthetics? Similarly, does retaction of the lower incisors in relationship to the chin in Class 111 cases detract from overall facial aesthetics? The Vertical Skeletal Pattern - in a borderline case one would be more likely to attempt camouflage in a low MM angle case rather than a high angle case as any molar extrusion as a result of mechanotherapy would be helpful in a low angle case. In high angle cases at the limits of orthodontic treatment any molar extrusion would rotate the mandible downwards and backwards and exacerbate both the vertical and anterioposterior discrepancy. It is worth noting that a lot of these patients have got an increased vertical dimension as they have already experienced vertical growth with a posterior rotation of the mandible and this is likely to continue during treatment in most high angle cases. The AP Discrepancy - will it be possible to displace the teeth sufficiently on the apical bases to disguise the skeletal discrepancy? Will it be possible to retract the upper incisors into a secure lower incisor edge to upper root centroid relationship? Would it be appropriate to consider advancement of the lower incisor edges to help this correction? The Transverse Discrepancy - if surgical treatment is needed for a co-existing transverse discrepancy or skeletal asymmetry it would probably be easier to tackle the AP discrepancy during the surgery as well.
Space Requirements - will crowding of the teeth take up all the extraction spaces, including the space needed to reduce the overjet? If so then camouflage would be difficult and surgery may be more appropriate.
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Summary of Orthodontic Camouflage for Skeletal Malocclusion in Borderline Cases
Acceptable result likely when following factors are present:
i) Average or low FMPA with average or reduced face height.
ii) Mild AP jaw discrepancy.
iii) Crowding of less than 4-6mm per arch.
iv) Normal soft tissue features nose, lips and chin.
v) No transverse skeletal problem.
Poor result likely if patient has the following factors:
i) Long vertical facial pattern with high FMPA and increased lower face height.
ii) Moderate or severe AP discrepancy.
iii) Crowding greater than 4-6mm per arch.
iv) Exaggerated facial features with prominent nose or chin or obtuse nasolabial angle.
v) If there is a transverse skeletal component to the overall malocclusion.
Indications for a Combined Orthodontic and Surgical Approach to Treatment
General factors:
i) Good general health suitable for surgery and general anaesthetic.
ii) Informed consent with the patient understanding the risks and benefits of surgery.
Factors relating to the malocclusion:
i) Severe Class II or Class III malocclusion.
ii) Deep overbite in non-growing patient.
iii) Skeletal anterior open bite.
iv) Extremes of vertical excess or deficiency in the maxilla or mandible.
v) Skeletal asymmetry.
Patients with the above problems may have the following complaints.
i) Concern regarding their facial or dental appearance. ii) Difficulty with eating or drinking.
iii) Gingival hyperplasia due to mouth breathing
iv) Trauma to the gingival tissues.
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The aims of treatment in combined orthodontic and surgical management are:
i) Good facial aesthetics. ii) Good dental aesthetics. iii) Functional occlusion. iv) Future health of the oral facial tissues. v) Stable result. vi) Minimum morbidity.
Extractions Patterns in Patients Being Prepared for Surgery. The importance of deciding on surgery or camouflage from the outset is further illustrated by the difference in extraction patterns needed in the two approaches.
The Surgical Management of Class 2 Patients The extraction pattern for the same patient would be quite different if mandibular advancement were being planned. i) The extraction of the lower first premolars to align the lower arch and decompensate for proclination of the lower incisors is often necessary. ii) The upper arch is often treated non-extraction, or by extraction of upper second premolars to avoid the retraction of the upper labial segment. iv) Class III elastics are often useful in decompensation.
The Surgical Management of Class 3 Patients The extraction pattern is typically as follows: i) The extraction of upper first premolars in crowded cases, allowing alignment of the arch and decompensation of the upper incisors. ii) The lower arch is typically treated non-extraction or in exceptional circumstances lower second premolars may be considered. iii) Class II elastics are helpful to aid decompensation.
In borderline cases if satisfactory aesthetics and functional occlusion can be achieved by either orthodontic camouflage or combined orthodontic and surgical treatment then each approach must be carefully explained so that an informed decision may be reached by the patient. Returning to a discussion of the patients concerns (in the form of a prioritised problem list) often helps to clarify the treatment expectations and suggest the appropriate treatment choice.
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Section 7 – Risks and Benefit Considerations in Orthodontics
See Modules 17 and 18.
Presentation of the Treatment Plan to the patient and parent to include Risks and Benefits of treatment before informed consent for the agreed treatment plan can be confirmed.
The last step of treatment planning is to present the proposed treatment to the patient and, if appropriate, their parent or guardian. Often there is more than one possible option and each should be presented to the patient with an explanation of the relative merits. The appliances to be used should be shown. The nature of the patient's role and responsibilities during treatment should be explained and in particular the compliance and effort required. Decalcification and periodontal damage if tooth brushing and dietary advice is not followed should be explained and if the treatment involves headgear or elastic traction, this should also be discussed. It is wise to overestimate treatment times. The potential risks of orthodontic treatment should be explained to the patient so that their informed consent to the treatment is obtained. However, it is important that any risks should be put in context. It may be helpful if some written material is provided to back up the information that is given at the consultation, and the patient is allowed some time to reflect upon the proposed treatment at home before reaching a decision on whether or not to go ahead.
Benefits 1. Improved facial aesthetics and improved psychosocial well being. Good evidence that this is an important benefit in patients with severe malocclusions.
2. Avoidance of trauma to prominent incisors
3. Decreased susceptibility to pathological migration of incisors
4. Avoidance of impaction of third molars
5. Avoidance of TMJ dysfunction - little evidence for this
6. Periodontal disease - little evidence that orthodontic treatment will help prevent periodontal disease in the future.
7. Caries - little evidence that orthodontic treatment will make the teeth less susceptible to decay.
Risks 1. Decalcification.
2. Periodontal disease
3. Loss of alveolar crest height.
4. Gingival recession. And root resporption
5. TMJ dysfunction? - little evidence for this
6. Risk of partial or complete treatment failure
7. Risk of relapse
8. Risks associated with extractions or surgery. eg Risk of GA
9. Risk of bacterial endocarditis in at risk patients.
The risks and benefits are to be considered fully so that an informed decision can be made.
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Section 8 – Summary of features important in Diagnosis and Treatment Planning
Refer to Module 14 – Diagnostic procedures for further reading.
• Patient complaints • Pathology • The A-P and vertical skeletal pattern and incisal inclinations • The transverse skeletal and dental relationships • Facial and Soft tissue profile • The Lips • The occlusion and arch form • TMD • Age and sex and Growth potential • Patient Compliance • Mixed dentition assessment
Having identified these features and understood the aetiology of the malocclusion develop the problem list
1. The Problem List The development of a prioritized problem list
• Patient’s concerns and motivation • Pathology • Skeletal Pattern in 3 planes • Soft Tissue relationships • Dentoalveolar including Tooth size discrepancies • Age and growth potential of the patient • Social Factors • Other
2. The Treatment Aims
3. The Treatment Plan
• Understand the principles of treatment planning • Understand the limitations of Orthodontic treatment • Determine the post treatment lower incisor position and stable arch form • Determinethe of space requirements • Extractions vs. non- extraction treatment and facial profile • Distal movement of molars • Enamel stripping • Expansion • Factors which influence the extraction choice within each category of crowding • The curve of Spee and crowding • The effect on available space by antero-posterior expansion/retraction • Treatment decisions for the “borderline” patient o Surgery / orthodontic o Extraction / non extraction • Appliances to be used. • Anchorage control and anchorage balance. • The prevention of lower labial segment crowding. • Retention
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By interpreting all the diagnostic data and taking into account the patient’s concerns, the aims of treatment and then a treatment plan can be identified. The key to treatment planning is to understand the aetiology of the malocclusion, which in turn helps to develop a problem list. The solutions to these problems can be listed in a structured manner, commencing with pathology. This list then helps to develop the aims of treatment and a chronological treatment plan, with the aims and plan being re-evaluated throughout treatment to ensure proper progress. Remember that it is not necessary to treat every malocclusion and the benefits to the patient should be carefully assessed prior to undertaking any orthodontic treatment.
Timing
The total time required for the Module and assessment is 20 hours.
Treatment Planning Slideshow
Essay Title:
Discuss the relative merits of the various techniques advocated for the reduction of increased overbite.
In addition - 60 minute essays: to be updated at intervals by individual schools: 1. Discuss the orthodontic decisions that have to be made when a 13 year old girl presents with an unerupted maxillary canine. 2. What factors may affect your choice of method of reducing a deep overbite in the treatment of a class 11 malocclusion. 3. Describe the differential diagnosis of Anterior Open Bite and indicate how your findings may affect treatment planning. 4. Discuss the process of treatment planning of a patient with a severe Class 111 malocclusion that will require a combined orthodontic and surgical approach.
It would be useful to look at the cases available in the BOS Members’ section - login required.
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Section 9 - Bibliography Ackerman JL, Proffit WR. Soft tissue limitations in orthodontics: Treatment planning guidelines Angle Orthodontist 1997; 67: 327-336.
Ackerman JL, Ackerman MB, Bresinger CM, Landis JR. A Morphometric analysis of the posed smile. Clin Orthod Res 1998; 1: 2-11.
Beattie JR, Paquette DE, Johnston LE. The functional impact of extraction and nonextraction treatments: A long-term comparison in patients with "borderline", equally susceptible Class II malocclusions. Am J Orthod Dentofac Orthop 1994; 105: 444-9.
Bernstein L. Edward H. Angle versus Calvin S. Case: Extraction versus nonextraction. Part I. Historical revisionism. Am J Orthod Dentofac Orthop 1992; 102: 464-470.
Bishara SE, Burkey PS. Second molar extractions: a review. Am J Orthod 1986; 89: 415-24.
Bishara SE, Jakobsen JR. Profile changes in patients treated with and without extractions: Assessments by lay people. Am J Orthod Dentofac Orthop 1997; 112: 639-44.
British Orthodontic Society. Young practitioner's guide to Orthodontics. 1996; BOS Office, 291 Grays Inn Road, London.
Canut JA, Arias S. A long-term evaluation of treated Class II division 2 malocclusions: a retrospective study model analysis. Eur J Orthod 1999; 21: 377-386.
Germane N and Staggers JA. Arch length considerations due to the curve of Spee: a mathematical model. Am J Orthod Dentofac Orthop 1992; 102: 251-5.
Gianelly AA, Cozzani M, Boffa J. Condylar position and maxillary first premolar extraction. Am J Orthod Dentofac Orthop 1991a; 99: 473-476.
Gianelly AA, Anderson CK, Boffa J. Longitudinal evaluation of condylar position in extraction and non- extraction treatment. Am J Orthod Dentofac Orthop 1991b; 100: 416-420. Gianelly AA. Arch width after extraction and non-extraction. Am J Orthod Dentofac Orthop 2003; 123: 25-8.
Gianelly AA. Extraction vs. non-extraction: Arch width and smile esthetics. Angle Orthod 2003; 73: 354-358.
Holdaway RA. Soft tissue cephalometric analysis and its use in orthodontic treatment planning. Part 1. Am J Orthod Dentofac Orthop 1983; 84: 1-28.
Holdaway RA. Soft tissue cephalometric analysis and its use in orthodontic treatment planning. Part 2. Am J Orthod Dentofac Orthop 1984; 85: 279-293.
Houston WJB, Edler R. Long term stability of the lower labial segment relative to the A-Pog line. Eur J Orthod 1990; 12: 302-310.
James RD. A comparative study of facial profiles in extraction and non-extraction treatment. Am J Orthod Dentofac Orthop 1998; 114: 265-76.
Johnson DK, Smith RJ. Smile aesthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofac Orthop 1995; 108: 162-7.
Johnston LE. The value of information and the cost of uncertainty: who pays the bill? Angle Orthod 1998; 68: 99-102.
Kerr WJ, Miller S, Dawber JE. Class III malocclusion: surgery or orthodontics? Br J Orthod 1992; 19: 21-24.
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Kirschen RH, O'Higgins EA, Lee RT. The Royal London Space Planning: An integration of space analysis and treatment planning Part 1. Am J Orthod Dentofac Orthop 2000; 118: 448-55.
Kirschen RH, O'Higgins EA, Lee RT. The Royal London Space Planning: An integration of space analysis and treatment planning Part 2. Am J Orthod Dentofac Orthop 2000; 18: 456-61.
Kokadereli I. The effect of first premolar extraction on vertical dimension. Am J Orthod Dentofac Orthop 1999; 116: 41-45.
Lai J, Ghosh J, Nanda RM. Effects of orthodontic therapy on the facial profile in long and short vertical facial patterns. Am J Orthod Dentofac Orthoped 2000; 118: 505-13.
Lee, R. T. (1999). Arch width and form: A review. Am J Orthod Dentofac Orthop 1991; 115: 305-13.
Livieratos FA, Johnston LE Jr. A comparison of one-stage and two-stage nonextraction alternatives in matched Class II samples. Am J Orthod Dentofac Orthop 1995; 108: 118-31.
Luecke PE, Johnston LE. The effect of maxillary first premolar extraction and incisor retraction on mandibular position: testing the central dogma of "functional orthodontics". Am J Orthod Dentofac Orthop 1992; 101: 4- 12.
Luppanapornlarp S, Johnston LE. The effects of premolar extraction: a long term comparison of outcomes in "clear-cut" extraction and non-extraction Class II patients. Angle Orthod 1993; 63: 257-272.
Mills JRE. Long-term results of the proclination of lower incisors. Br Dent J 1966; 120: 355-363.
Mills JRE. The stability of the lower labial segment. Dent Pract Dent Rec 1968; 18: 293-306.
NHS Centre for Reviews and Dissemination, York. Prophylactic removal of impacted third molars: is it justified? Br J Orthod 1998; 26: 149-51.
Noroozi H, Djavid GE, Moeinzad H and Teimouri AP. Prediction of arch perimeter changes due to orthodontic treatment. Am J Orthod Dentofac Orthop 2002; 122: 601-607.
Ong HB, Woods MG. An occlusal and cephalometric analysis of maxillary first and second premolar extraction effects. Angle Orthod 2001; 71: 90-102.
Paquette DE, Beattie JR, Johnston LE Jr. A long-term comparison of nonextraction and premolar extraction edgewise therapy in "borderline" Class II patients. Am J Orthod Dentofac Orthop 1992; 102: 1-14.
Park YC, Burstone CJ. Soft - tissue profile - fallacies of hard tissue standards in treatment planning. Am J Orthod 1986; 90: 52-56.
Saelens NA, De Smit AA. Therapeutic changes in extraction versus non-extraction orthodontic treatment. Eur J Orthod 1998; 20: 225-230.
Selwyn-Barnett BJ. Class II division 2 malocclusion: A method of planning and treatment. Br J Orthod 1996; 23: 29-36.
Shearn BN, Woods MG. An occlusal and cephalometric analysis of lower first and second premolar extraction effects. Am J Orthod Dentofac Orthop 2000; 117: 351-61.
Spyropoulos MN, Halazonetis DJ. Significance of the soft tissue profile on facial aesthetics. Am J Orthod Dentofac Orthop 2001; 119: 464-71.
Staggers JA. A comparison of second molar and first premolar extraction treatment. Am J Orthod Dentofac Orthop 1990; 98: 430-6.
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Steyn CL, Harris AMP, du Preez RJ. Anterior arch circumference adjustment - how much? Angle Orthod 1996; 66: 457-462.
Tanaka MM, Johnston LE. The prediction of the size of unerupted canines and premolars in a contemporary orthodontic population. J Am Dent. Assoc 1974; 88: 798.
Waters D. A cephalometric comparison of maxillary second molar extraction and non-extraction treatment Am J Orthod Dentofac Orthop Abstract 2001; p 457.
Young TM, Smith RJ. Effects of orthodontics on the facial profile: a comparison of changes during non- extraction and premolar extraction treatment. Am J Orthod Dentofac Orthop 1993; 103: 452-8.
Zierhut EC, Joondeph DR, Artun J, Little RM. Long-term profile changes associated with successfully treated extraction and non-extraction Class II div I malocclusions. Angle Orthod 2000; 70: 208-19.
Assessment
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