enigma of class II molar finishing.pdf

American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 6

experience, it is doubtful that patients treated with spaceopening and prosthetic replacements will have better longterm treatment results than those treated with orthodontic space closure. The question to be answered by controlled clinical studies in the future will be: what is preferable in a life-long perspective for the patient, either a natural “living” root or an ankylosed foreign body in the site of the missing maxillary lateral incisor? In this letter, we have focused on the permanence of replacements for missing maxillary lateral incisors. Treatment decisions for young people with missing incisors should be based on a comprehensive assessment that includes many factors.14 For many patients, the best results can be obtained by an interdisciplinary approach including implants or cantilever prosthetics. The challenge is, however, to plan treatment according to the patient’s needs and diagnosis, and not on the assumption that implants are superior to orthodontically positioned and reshaped natural teeth. Bjorn U. Zachrisson, DDS, MSD, PhD Arild Stenvik, DDS, MSD, PhD Oslo, Norway 0889-5406/$30.00 doi:10.1016/j.ajodo.2004.10.006

REFERENCES 1. Turpin DL. Treatment of missing lateral incisors. Am J Orthod Dentofacial Orthop 2004;125:129. 2. Wilson TG Jr, Ding TA. Optimal therapy for missing lateral incisors? Am J Orthod Dentofacial Orthop 2004;126(3):22A23A. 3. Thilander B, Odman J, Lekholm U. Orthodontic aspects of the use of oral implants in adolescents: a 10-year follow-up study. Eur J Orthod 2001;23:715-31. 4. Iseri H, Solow B. Continued eruption of maxillary incisors and first molars in girls from 9 to 25 years studied by the implant method. Eur J Orthod 1996;18:245-56. 5. Oesterle LJ, Cronin RJ Jr. Adult growth, aging, and the singletooth implant. Int J Oral Maxillofac Implants 2000;15:252-60. 6. Chang M, Wennström JL, Odman P, Andersson B. Implant supported single-tooth replacements compared to contralateral natural teeth. Crown and soft tissue dimensions. Clin Oral Impl Res 1999;10:185-94. 7. Tuverson DL. Close space to treat missing lateral incisors. Am J Orthod Dentofacial Orthop 2004;125(5):17A. 8. Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin Orthod 2001;35:221-34. 9. Weichbrodt DJ, Stenvik A, Haanæs HR. An intra-individual evaluation of implant supported single tooth replacements for missing maxillary incisors (abstract). 18th Congress of the Nordic Association of Orthodontists, Loen, Norway, September 4-7, 2003. 10. Thordarson A, Zachrisson BU, Mjör IA. Remodeling of canines to the shape of lateral incisors by grinding: a long-term clinical and radiographic evaluation. Am J Orthod Dentofacial Orthop 1991;100:123-32. 11. Wennström J. Personal communication 2004. 12. Esposito M, Ekestubbe A, Gröndahl K. Radiological evaluation of marginal bone loss at tooth surfaces facing single Brånemark implants. Clin Oral Impl Res 1993;4:151-7. 13. Andersson B, Odman P, Lindvall AM. Single-tooth restorations

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on osseointegrated implants: results and experiences from a prospective study after 2-3 years. Int J Oral Maxillofac Implants 1995;11:311-21. 14. Stenvik A, Zachrisson BU. Orthodontic closure and transplantation in the treatment of missing anterior teeth. An overview. Endod Dent Traumatol 1993;9:45-52.

Enigma of Class II molar finishing The orthodontic literature, from the days of Bolton,1 contains ample articles about correction of the anterior segment, with the molars finished in a Class II relationship. Particularly noteworthy are the patients with Class II malocclusions who are treated with extractions only in the maxillary arch. In a well-written thesis, Kessel2 argued that, in nongrowing patients (above 12 years) with a particular type of Class II malocclusion, single-arch extraction is a justifiable method of treatment. Standard textbooks like those of Bishara3 and Proffit4 also document cases in which the molars were left in a Class II relationship at the end of the treatment. A recent article in the AJO-DO, “Class II treatment success rate in 2- and 4-premolar extraction protocols” (Janson G, Brambilla AC, Henriques JFC, de Freitas MR, Neves LS. Am J Orthod Dentofacial Orthop 2004;125:472-9), compares Class II patients treated with single-arch and both-arch extractions and concluded that the former was better. What intrigues me is that, for a century, we orthodontists have made the correction of Class II molar relationships a top priority. Whether we used a myofunctional approach, comprehensive fixed appliances, or even surgical treatment, finishing with the molars in a Class I relationship was considered almost mandatory. But were we chasing the wrong treatment goal? Was Angle wrong in assigning a malocclusion label to the Class II molar relationship? Is the first part of Andrews’ first key to normal occlusion worth ignoring? As a great admirer of tooth size and morphology in relation to malocclusion and treatment results, I find it very difficult to accept Class II molar finishing. Bolton’s tooth size ratio has shown us that proper maxillary and mandibular tooth size and proportion are essential for a normal occlusal relationship. The importance of the anterior ratio is well understood and applied clinically. In essence, 3 maxillary anterior teeth occlude with 3.5 mandibular anterior teeth in each quadrant for a normal anterior relationship—ie, overjet, overbite, and midline. It can also be interpreted that maxillary anterior teeth in the outer arc have a larger mesiodistal dimension than the mandibular ones. The size of anterior teeth in normal circumstances is designed to give overjet, overbite, midline, and canine occlusion. It is possible to extrapolate a similar posterior ratio from the overall ratio of Bolton. From the 77% anterior ratio, mandibular teeth (first molar to first molar) pick up to become 91% value in the overall ratio. Logically and factually, the mandibular posterior teeth are larger mesiodistally than the maxillary posteriors. Five maxillary posterior teeth (first

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premolar to third molar) occlude with 4.5 mandibular posterior teeth when third molars are present. If the third molars are not considered, 4 maxillary posterior teeth (first premolar to second molar) occlude with 3.5 mandibular posteriors. Because the shape of the posterior arch is not an arc, maxillary teeth might not require extra arch length. Nature’s design of posterior tooth size agrees with normal (Class I) intercuspation for balanced functioning as the best form-and-function interrelationship. In Class II malocclusion, a distal step at the posterior end of the occlusion is the least desirable goal of orthodontics, and also Class III with a mesial step at the distal end. With this background in mind, if we analyze Class II molar relationships, it will be seen that the distal half of the mandibular third molars (if present) or the distal half of the mandibular second molars will have no functioning occlusal contact. This can be verified clinically if we see the distal end of occlusion carefully and verify study models for the same. Thus, it can be conclusively shown that a Class II molar relationship is not tenable morphologically. Kessel’s argument2 stops at the mesial cusp of the maxillary first molar without looking beyond it. But out of sight can’t be out of mind. At the start of his thesis, Kessel also elaborates on the difficulty of correcting Class II molar relationships, subscribing to the “if you can’t beat ‘em, join ‘em” policy. Kessel’s arguments, at best, are compromises. Correcting only the visible components of malocclusion—ie, overjet and proclination, and leaving behind proper intercuspation of the posterior teeth—is not becoming of a professional orthodontist. As guardians of occlusion, orthodontists cannot leave the large distal half of a mandibular molar without occlusal contact in centric occlusion. Let the experts in functional occlusion and gnathology comment on the implications of only the mesial half of the mandibular second molar having an occluding antagonist while the distal half is left nonfunctional. It might not supraerupt, but equilibrium and stability are the questions. Far-reaching implications of an imbalanced posterior occlusion on TMJ function must be explored. It may be one thing to accept Class II molar finishing in compromised, mutilated, or adult orthodontic patients. But eliminating molar Class II correction from the treatment objectives altogether goes against century-old orthodontic teaching and preaching. The current implication of “better occlusal success rate” (with a 2-premolar extraction “protocol” than with 4 premolar extractions) Class II molar finish stretches the limit a step further. Left unquestioned, in the next decade, we might see “attainment of Class II molar relationship” as a desirable treatment objective! Class II molar relationships are not tenable morphologically or physiologically. Our illustrious predecessors couldn’t have been wrong in spending maximum energy and strategy in trying to resolve them. Jayaram Mailankody, MDS Calicut, Kerala, India 0889-5406/$30.00 doi:10.1016/j.ajodo.2004.10.007

American Journal of Orthodontics and Dentofacial Orthopedics December 2004

REFERENCES 1. Bolton WA. Clinical applications of a tooth size analysis. Am J Orthod 1962;48:504-29. 2. Kessel SP. The rationale of maxillary premolar extraction only in Class II therapy. Am J Orthod 1963;49:276-93. 3. Bishara SE. Textbook of orthodontics. Philadelphia: W. B. Saunders/Harcourt; 2001. p.359. 4. Proffit WR. Contemporary orthodontics. 3rd ed. Saint Louis: Mosby/Harcourt; 2000. p. 274.

Author’s response Thank you for your comments and for sharing your perspectives on our article, “Class II treatment success rate in 2- and 4-premolar extraction protocols.” Because a debate is suggested, I would like to answer some of your concerns. Were we chasing the wrong treatment goal? No, we were chasing the right treatment goal for that time in Class II malocclusion cases. Initially, it was thought and taught that molars should always finish in a Class I relationship.1-5 Later, many orthodontists realized and researchers proved that, in some Class II malocclusions, the molars could be finished in a Class II relationship without unfavorable collateral effects.6-11 Enough clinical and scientific evidence has been provided to support finishing treatment of certain Class II malocclusions with molars in a Class II relationship. Was Angle12 wrong in assigning a “malocclusion” label to the Class II molar relationship? No, Angle was not wrong—if a full complement of teeth is present in an untreated natural denture or the corresponding dental units have been extracted in both dental arches. Is the first part of Andrews’ first key to normal occlusion worth ignoring? No, not when the treatment plan involves finishing with the molars in a Class I relationship. This is the treatment goal when treating nonextraction13 or when treating by extracting corresponding dental units in both arches.14,15 However, if the treatment plan consists of only 2 maxillary premolar extractions, the molars will finish in a Class II relationship.16 This is nowadays so widely accepted that Andrews has designed a first maxillary molar tube with specific rotation to perfectly fit into a Class II molar relationship at the end of treatment.16,17 Additionally, there is no evidence in the literature that finishing with a Class II molar relationship has any implications for treatment stability18-20 and TMJ problems.21-27 Our findings showed that a 2-premolar extraction protocol in complete Class II malocclusions provided a better occlusal success rate than a 4-premolar extraction protocol, but this by no means suggests eliminating Class II molar correction in every situation. Rather, the findings demonstrate that the 2 maxillary-premolar extraction protocol in complete Class II malocclusions, in general, provides a better occlusal success rate because it depends less on patient compliance, as previously suggested.6,17 Therefore, it alerts the orthodontist to the great difficulty of the 4-premolar extraction approach in