Maxillary Second Molar Extractions in Orthodontic

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Wilson Lee, BDS, BSc, MOrth, MAXILLARY SECOND MOLAR MOrth RCS (Edin)1

EXTRACTIONS IN ORTHODONTIC Ricky Wing-Kit Wong, BDS, MOrth, PhD, MOrthRCS, TREATMENT FRACDS2

Tomio Ikegami, DDS, Cert This article is a review of the rationales, indications, methods, and Pedo, Cert Orth, MSc, effects of orthodontic treatment with maxillary second molar extrac- Dip ABO3 tions. In addition to the patient’s malocclusion, specific considera- tions about the status and position of the maxillary second and third Urban Hägg, DDS, Odont molars should be taken into account. In recent years, the develop- Dr, FDSRCS (Edin)4 ment of temporary anchorage devices, in addition to extraoral traction and intraoral distalization appliances, has become another arma- mentarium in the distalization of the maxillary posterior teeth, which may affect the selection of teeth to be extracted from second to third molars. In conclusion, extraction of maxillary second molars is a viable option in selected cases at present, but it is important to understand the indications and limitations of this treatment choice. World J Orthod 2008;9:52–61.

1Advanced Diploma student, Disci- pline of Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China; private practice of orthodontics, Hong he maxillary second molars are not a NORMAL DEVELOPMENT OF Kong SAR, China. Tcommon choice for extraction in ortho- MAXILLARY SECOND 2Associate Professor, Discipline of dontic treatment. The first comprehen- MOLARS Orthodontics, Faculty of Dentistry, sive review of the role of maxillary second The University of Hong Kong, Hong Kong SAR, China. molar extractions in orthodontic treat- On average, the calcification of the maxil- 3Honorary Clinical Associate Profes- 1 ment was published in 1939, while the lary permanent molars commences at sor, Discipline of Orthodontics, Fac- most recent was published in 1996.2 2.5 to 3 years of age. The crown is fully ulty of Dentistry, The University of The purpose of this article is to review formed at 7 to 8 years, and the tooth Hong Kong, Hong Kong SAR, China; contemporary views about this treatment private practice of orthodontics, erupts at 12 to 13 years of age, with its Kumamoto, Japan. 9 option. Previously published reports on final root formation at 14 to 16 years. 4Chair and Professor, Discipline of extraction of the second molars were pri- According to a study by Ling,10 the aver- Orthodontics, Faculty of Dentistry, marily based on the authors’ personal age mesiodistal crown diameter of the The University of Hong Kong, Hong clinical experience rather than evidence- maxillary second molar of a 12-year-old Kong SAR, China. 3,4 based research. While most of the Southern Chinese child is 10.3 mm in CORRESPONDENCE reports referred to cases treated with the males and 10.0 mm in females. In Cau- Dr Wilson Lee extraction of all 4 second molars,5–7 only casians of the same age, it is 10.4 mm in Discipline of Orthodontics 1 report was about extraction of only the boys and 9.8 mm in girls.11 Faculty of Dentistry maxillary second molars.2 The last com- The University of Hong Kong 2/F, Prince Philip Dental Hospital prehensive review of the literature on 34 Hospital Road extraction of second molars in orthodon- Sai Ying Pun tic treatment was 20 years ago.8 Hong Kong SAR, China

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Table 1 Indications and contraindications of maxillary second molar extraction in orthodontic treatment Indications Class II molar and canine relationship with good facial profile Deep overbite Posterior crowding and/or mild anterior crowding Grossly carious, periodontally involved, or ectopically erupted maxillary second molars Distally tilted developing maxillary third molars Contraindications Excessively protrusive facial profile Agenesis of permanent teeth Grossly restored, carious, or periodontally involved maxillary first permanent molars

RATIONALE FOR MAXILLARY upper lip and prognathic maxilla are also SECOND MOLAR EXTRACTION present, extraction of the maxillary first premolars will reduce lip protrusion; how- The main indication for extraction of ever, this option increases the danger of teeth in orthodontic treatment is to cre- root resorption during space closure, due ate space. Various rationales for the to the large amount of root torque selection of maxillary second molar required to move the roots of the maxil- extraction are reviewed in the following lary incisors into a more palatal posi- sections and summarized in Table 1. tion.16 By extracting the maxillary second molars, this problem can be avoided because the orthodontic tooth movement Orthodontic camouflage of Class is slow with simultaneous distalization of II malocclusion all maxillary teeth, allowing bone remod- eling along the maxillary incisor roots to Extraction of maxillary second molars take place. It also allows more efficient was once suggested to be indicated for torque control of the maxillary incisors.17 the correction of Class II division 1 malocclusion, provided there was excessive labial inclination of the maxillary incisors Facial profile with no spacing and minimal overbite and the unerupted maxillary third molars Extraction of the maxillary second molars were in good position and of proper has become a popular treatment option shape.12 The diagnostic space-manage- when there is concern about the poten- ment guidelines of the Tweed-Merrifield tial adverse effect upon the facial profile philosophy indicated this option in cases with extraction of the maxillary first pre- of mild skeletal Class II pattern with an molars. Maxillary second molars are ANB angle between 5 and 8 degrees.13 located in the posterior part of the arch; This extraction option is also suitable for therefore, the extraction of these teeth patients with a skeletal Class II malocclu- will have less effect on the positioning of sion, as dentoalveolar compensation, in the maxillary incisors during orthodontic those cases for whom bite-jumping is not treatments than would extraction of the recommended because of a prognathic maxillary premolars.18 Thus, extraction of maxilla and near-correct anterior-poste- the maxillary second molars is indicated rior positioning of the mandible.2,14,15 when a so-called “dished-in” appearance Patients with Angle Class II division 2 of the face at the end of facial growth malocclusions have retroclined maxillary should be avoided.15 incisors and deep overbite. If a protrusive

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a b c

d ef

Fig 1 Treatment sequence of a female, 12 years 9 months of age, with an Angle Class II division 1 malocclusion. (a) Pretreat- ment. (b) After 6 months of cervical headgear. (c) After 2 years of headgear treatment. Note that the axial inclination of the maxillary incisors was corrected as the posterior teeth were distalized. (d) Fixed appliance, worn for 3 months. (e) Finishing stage with the multiloop edgewise archwire technique. (f) Posttreatment.

Distalization of the buccal segment If the developing maxillary third molars encounter a lack of space for Extractions of the maxillary second eruption, the space created after extrac- molars and distalization of maxillary pos- tion of the maxillary second molars can terior teeth may be indicated in patients provide space not only for the distaliza- with a good facial profile and skeletal tion of the posterior teeth, but also for Class I pattern but who have Class II the eruption of the maxillary third molars. molar and canine relationships, moder- Research has shown that, in general, the ate maxillary arch crowding, and mild maxillary third molars will erupt favorably mandibular arch crowding.19 This is par- in such cases.20 Simple extraction of the ticularly true in patients with retroclined maxillary second molars may prevent maxillary and mandibular incisors. The possible trauma arising from the surgical extraction of the maxillary second molars removal of eventually impacted maxillary provides the space required for align- third molars. ment of the teeth and for attaining cor- A sample case is presented in Figs 1 rect occlusal relationships, as well as to 3 to demonstrate the successful man- facilitating the distal movement of the agement of severe Angle Class II division maxillary posterior teeth. 1 malocclusion, with extraction of maxil- In cases of severe posterior crowding lary second molars combined with head- in the maxillary arch, extraction of the gear treatment and fixed appliances. maxillary second molars may also be indicated. In some complex cases, it may become necessary to extract the maxillary first premolars, as well.

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abc

d e f

g hi

Fig 2 Lateral profiles, frontal profiles, and overjet: (a to c) Pretreatment. (d to f) Posttreatment. (g to i) Ten years posttreatment.

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c d

e f

Fig 3 Panoramic radiographs. (a) Pretreatment. (b) Nine months after headgear treatment. (c) Sixteen months after headgear treatment. (d) Three years after the start of headgear treatment. (e) Posttreatment. Note the positioning of the maxillary third molars. (f) Retention (3 years 9 months posttreatment).

Condition of the maxillary second CONTRAINDICATIONS molars Agenesis, or severe mesioangulation, of When the maxillary second molars are the maxillary third molars is a contraindi- grossly carious, periodontally compro- cation of orthodontic treatment with mised, or ectopically erupted,21 their extraction of the maxillary second molars extraction can also be considered as a (see Table 1). The general pattern of max- treatment option. illary third molar eruption is downward

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and forward21; an ideal maxillary third DISADVANTAGES molar will have a slight distoangular position that will allow it to rotate mesially as The following are disadvantages of the it descends into the occlusion. maxillary molar extraction treatment Orthodontic treatment with maxillary option: (1) too much tooth substance second molar extraction requires distal- removed in Class I malocclusions with ization of the maxillary first molars, which mild crowding15,24; (2) extraction sites may result in some bite opening; there- are far from the area of concern in mod- fore, it may be contraindicated in patients erate-to-severe anterior crowding15; (3) with open bite. Patients with a maxillary extraction sites are of no help in the cor- protrusive facial profile would likely bene- rection of anteroposterior discrepancies fit more from extraction of the maxillary without patient cooperation in wearing first premolars, since conventional distal- extraoral appliances capable of moving ization would eventually result in posterior the dentition “en masse” distally; (4) rotation of the mandible, thus increasing potentially insufficient size and form of the lower facial height and worsening the these molars24; and (5) unpredictable facial appearance. The use of the new path of eruption of maxillary third temporary anchorage devices (TADs) molar.26 seems to have the potential to reduce these adverse effects by providing vertical control. OPTIMAL TIMING FOR EXTRACTIONS

ADVANTAGES Ideally, maxillary second molars should be extracted when the maxillary third From the literature, the following reasons molars reach the vertical midline of the are proposed as the major advantages of maxillary second molar root in a Class I maxillary second molar removal: (1) no malocclusion.27 In a Class II malocclu- excessive retrusion of the maxillary ante- sion, because treatment often needs dis- rior teeth and normalization of maxillary talization of the maxillary first molars, the incisor inclination during retraction, com- maxillary third molars should be approxi- pared to maxillary first premolar extrac- mately at the level of the cementoenamel tion, and hence less adverse change of junction of the maxillary second molars profile in cases of mild Class II malocclu- at the time of extraction.27 The maxillary sion with mild crowding22; (2) better sta- third molars should be developed to their bility of treatment results23,24; (3) avoid- bifurcation before extraction of the maxil- ance of maxillary molar staggering and lary second molars.9 impaction22; (4) facilitation of maxillary first molar distal movement15; (5) distal movement of the maxillary dentition only, CHANGES IN MAXILLARY as needed to correct the overjet and max- THIRD MOLAR POSITION illary crowding; (6) no trauma of maxillary third molar extraction22; and (7) preser- With proper diagnosis and careful treat- vation of more the patient’s complete ment planning, most maxillary third dentition, from right molars to left molars would erupt successfully into molars, compared with extraction of all good position.25,27 After extraction of the first premolars. maxillary second molars, the maxillary It has been demonstrated that the third molars rotate and tip mesially with extraction of maxillary second permanent descent; the greater the original distal molars can be effective in many cases angulation, the greater the amount of where removal of maxillary first or sec- rotation.20 ond premolars would otherwise be Recent research has shown that max- recommended.25 illary third molars uprighted and accept- ably replaced maxillary second molars after extraction for orthodontic purposes

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in 95% of such-treated cases.27 Unsuc- who had extraction of maxillary second cessful eruption of the maxillary third molars. Primarily angular measurements molars has been shown to be due to were used in the cephalometric analysis; prior excessive mesial tilting or lack of however, the linear measurements proximal contact.27 showed that both upper lips and maxil- The eruption prognosis of the maxillary incisors were significantly retracted. lary third molars improves when they This study did not include any control have a favorable inclination, with a 15- to group. 30-degree angle distal to the long axis of Staggers6 examined treatment results the maxillary first molars.21,23 The mesial of maxillary and mandibular second surface of the unerupted maxillary third molar extraction cases and compared molars should be “fairly in line horizontally them with treatment results of maxillary with the distal surface of the mandibular and mandibular first premolar extraction second molars.”21 cases. The results showed that the 2 With proper selection of cases, the groups had fewer differences than often form and size of the erupted maxillary indicated by advocates of second molar third molars after orthodontic treatment extraction. However, the maxillary and with extraction of the maxillary second mandibular incisors and the lower lip in molars was acceptable nearly 90% of the the premolar extraction group were time; all maxillary third molars erupted retracted significantly more than those in with mesial contact, and in 90% of the the maxillary second molar group. The cases, the maxillary third molars had resulting facial profile after extraction of acceptable axial inclination and position second molars appears to have no signifi- without the need for further alignment.2 cant difference from that obtained after Bennett and McLaughlin28 concluded extraction of first premolars. However, that the pantomographic evaluation of this comparison would only be valid if the the changes in third-molar angulation amount and site of crowding were similar before and after orthodontic treatment in both groups, factors that were not with extraction of all second molars were mentioned in the study.28 The average not statistically different. In both groups, treatment time did not differ statistically the maxillary third molars showed an between the groups. improvement in angulation, while the Waters and Harris29 conducted a retro- mandibular third molars showed an spective cephalometric study to compare undesirable increase in angulation. A the nature of the skeletodental correction recent study by De-la-Rosa-Gay et al27 of maxillary second molar extraction and reported similar results. nonextraction treatments in correcting Class II malocclusions. The sample com- prised Class II, deep-bite, low-angle ado- EFFECTS OF ORTHODONTIC lescents; half were treated with maxillary TREATMENT WITH second molar extraction and half were EXTRACTION treated without extraction. Pitchfork analysis30,31 was used to evaluate sagit- Few studies have investigated the effects tal changes (in mm) of the teeth and sup- of extraction of maxillary second molars porting bones, relative to the functional in orthodontic treatment. These studies occlusal plane. There was no significant had different treatment objectives and difference in the dentofacial morphology the characteristics of the samples were between the 2 groups at the start of different.2,6,29 treatment. Several skeletodental treat- One of the objectives of extracting ment changes differed significantly maxillary second molars is to minimize between the 2 groups. The maxillary sec- the change in patient profile after ortho- ond molar extraction group exhibited dis- dontic treatment. Basdra et al2 did a pre- tal movement of the maxillary first and posttreatment cephalometric analy- molars (1.2 mm vs 0.0 mm), and there sis of 32 young patients (mean age of was greater flaring of the mandibular 14.6 years) with Class II malocclusion incisors in the nonextraction group (9.1

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degrees vs 3.5 degrees). The maxillary They mentioned that distalization of max- incisor roots were torqued lingually in illary posterior teeth with the extraction both groups, but there was more anterior of maxillary second molars will reduce crown movement in the nonextraction the treatment duration compared to group (2.0 mm vs 0.0 mm). Sagittal nonextraction treatment. Various types of molar correction in the maxillary second distalization appliances were discussed, molar group was a result of distalizing of including headgears, acrylic cervical the maxillary first molars to correct the occipital, transpalatal arch, Wilson bimet- malocclusion in the nonextraction group. ric distalizer, Herbst, Jasper jumper, and On average, the extraction group finished pendulum. It was concluded that if active treatment 7 months earlier than patient compliance was good and the nonextraction group. It was con- anchorage demand was maximum, the cluded that in properly selected Class II use of extraoral traction for distalization malocclusions, extraction of maxillary of the maxillary first molars was the best second molars is a viable alternative treatment option. However, the use of treatment choice. TADs for maxillary distalization of molars was not mentioned. At present, there are no scientifically EXTRACTION IN CONJUNCTION viable data available to compare the WITH FIXED APPLIANCE long-term results of similar malocclusions THERAPY corrected with maxillary premolar vs maxillary second molar extractions. Rix32,33 showed that sometimes the extractions of 4 premolars provided more space than was actually needed in Class EXTRACTION IN CONJUNCTION II division 1 malocclusions with borderline WITH TADS crowding of the mandibular incisors. As a result, he recommended the extraction of Temporary anchorage devices have 4 second molars in conjunction with become increasingly popular in orthodon- monobloc therapy as a better alternative. tic treatment. There have been recent In a study on extraction of maxillary studies discussing the effects of TADs in and mandibular second molars in 78 distalization of maxillary posterior teeth patients with Class II malocclusions, 21 with or without the extraction of maxillary patients had no orthodontic treatment, 9 second or third molars.36–40 A study by patients were treated with activators with Sugawara et al38 reported that the aver- springs to move the first molars distally, age amount of distalization of the maxil- and 48 had fixed appliances.34 It was lary first molars was 3.8 mm at the crown stated that the advantages of this level and 3.2 mm at the root level. Kyung method of treatment included ease in et al39 reported the use of a midpalatal distally moving mandibular first molars if microscrew together with a transpalatal they were mesially tipped, the rapid and arch to distalize the maxillary first complete eruption of the third molars, molars, illustrated with 2 case reports. In and complete space closure of the these 2 young patients, the maxillary extraction sites. The limitation of this molars moved distally 5 mm from the approach is the assumption of the pres- crowns and 3.5 mm from the apices ence and proper eruption of the third within 3 to 5 months, without the extrac- molars. Moreover, moving mandibular tion of second molars. first molars distally can be mechanically Gelgor et al41 investigated the efficiency difficult and, in Class II cases, there is of intraosseous screws for anchorage in the need to move all the anterior and maxillary molar distalization and the sagit- posterior permanent teeth distally for the tal and vertical skeletal, dental, and soft correction of overjet. tissue changes after maxillary molar distal- Sfondrini et al35 did a comprehensive ization using intraosseous screw-sup- analysis of the effect of maxillary molar ported anchorage. An anchorage unit was distalization with various appliances. prepared for molar distalization by placing

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Table 2 Summary of effects expected after maxillary second molar extraction in orthodontic treatment Effect Extraoral Increase in upper lip–to–E-line; more palatal root torque but less anterior crown movement than in nonextraction group Vertical No reported change in vertical relationship Dental Ninety-six percent of maxillary third molars will erupt into good position Transverse No change

an intraosseous screw behind the incisive posterior part of the arch and facilitates canal at a safe distance from the mid- eruption of maxillary third molars (Table 2). palatal suture, following the palatal It is important to consider the biologi- anatomy. The screws were placed and cal and mechanical requirements and immediately loaded to distalize the maxil- consequences of a particular treatment lary first molars; the maxillary second plan for both short- and long-term results, molars were present. The average distal- as well as the effects of these decisions ization time to achieve an overcorrected on the duration of treatment, facial pro- Class I molar relationship was 4.6 file, periodontal tissues, and functional months. The skeletal and dental changes occlusion. To determine the possible were measured on cephalograms and advantages of maxillary second molar dental casts obtained before and after extraction versus other extraction and the distalization. Analysis of the lateral nonextraction concepts, there is a need cephalograms showed that, on average, for randomized clinical trials that evalu- the maxillary first molars were tipped 8.8 ate and compare both short- and long- degrees and moved 3.9 mm distally. Mea- term treatment outcomes. surements of the dental casts showed a mean distalization of 5.0 mm. The maxillary first molars were rotated disto- REFERENCES palatally. On average, mild protrusion (mean 0.5 mm) of the maxillary central 1. Chapin WC. The extraction of maxillary second incisors was also recorded. However, molars to reduce growth stimulation. Am Orthod Oral Surg 1939;11:1072–1078. there was no change in overjet, overbite, 2. Basdra EK, Stellzig A, Komposch G. Extraction or mandibular plane angle measure- of maxillary second molars in the treatment of ments. It was concluded that the immedi- Class II malocclusion. Angle Orthod 1996;66: ately loaded intraosseous screw-sup- 287–292. ported anchorage unit was successful in 3. Harnick DJ. Case report: Class II correction using a modified Wilson bimetric distalizing achieving sufficient maxillary molar distal- arch and maxillary second molar extraction. ization without major anchorage loss. Angle Orthod 1998;68:275–280. 4. Dickson JA, Jones AG. Extraction of four second permanent molars in the presence of severe CONCLUSIONS premolar crowding: A case report. Dent Update 1996;23:339–340, 342-333. 5. Smith R. The effects of extracting upper sec- This review discussed a number of issues ond permanent molars on lower second perma- related to maxillary second molar extrac- nent molar position. Br J Orthod 1996;23: tions, including the indications, con- 109–114. traindications, advantages, disadvan- 6. Staggers JA. A comparison of results of second molar and first premolar extraction treatment. tages, optimal timing for extraction, as Am J Orthod Dentofacial Orthop 1990;98: well as how it affects the eruption of max- 430–436. illary third molars. The reviewed literature 7. Wilson HE. Angle’s Class II, Division 2. Dent strongly suggests that in carefully Pract 1964;14:245–255. selected cases, the extraction of maxillary 8. Bishara SE, Ortho D, Burkey PS. Second molar extractions: A review. Am J Orthod 1986;89: second molars relieves crowding in the 415–424.

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