Extreme dentoalveolar compensation in the treatment of Class III malocclusion

The satisfactory occlusal and esthetic results obtained were due to significant dentoalveolar compensation and excellent patient compliance with elastics. With such a large initial dental and skeletal A-P discrepancy, one would rarely think of dentoalveolar compensation.4,5 The changes contributing most to the correction were maxillary incisor proclination, and the extrusion and bodily retrusion of the mandibular incisors with concurrent alveolar remodeling. These changes produced a counterclockwise rotation of the occlusal plane as expected (Table).6 Obviously, a surgical approach would have produced even better occlusal and esthetic results.5,7 The patient was reluc-tant to undergo surgery, and she demonstrated a very compliant attitude toward the treatment demands. Although there are many nonsurgically treated adult Class III case reports,8-12 few show such significant dental and skeletal discrepancies.6 It is not expected that the dentoalveolar portions of the maxilla and the mandible will respond with significant remodeling
after incisor movement.13-15 It is speculated that alveolar response to incisor movement resulted from the bracket system and the mechanics. Maxillary and mandibular preadjusted incisor brackets for Class III treatment usually have accentuated labial and lingual crown torque, respectively, to compensate for the A-P basal-bone discrepancy.16-18 However, in the Biofunctional technique, the torque on these teeth is reversed; ie, there is accentuated lingual crown torque on the maxillary incisors and accentuated labial crown torque on the mandibular incisors.19 As the Class III elastics apply forces tending to tip the maxillary incisors labially and the mandibular incisors lingually, the built-in torque counteracts their effect, and the teeth are subjected to bodily movement. Perhaps this bodily movement induces a greater alveolar remodeling response.20,21 Besides counteracting the Class III elastic effects, these torques tend to correct initial incisor inclination, especially in the mandibular arch.22 Our results show that the torques
maintained the mandibular incisor inclination. However, despite the compensating lingual torque in the maxillary brackets, the Class III elastic force still
caused proclination of these teeth (Figs 9 and 10; Table).
Dentoalveolar changes improved the soft tissue profile, with protrusion of the upper lip and slight retrusion of the lower lip (Figs 6 and 9); this is usually
expected in camouflage treatment.6,23 Because the initial transverse discrepancy was only mild,24 the bilateral posterior crossbite was corrected
by widening the maxillary archwires and using intermaxillary  elastics. When such dramatic dentoalveolar changes are observed, a main concern is periodontal support.13 For maxillary incisors, the secondary effects could include resorption of the labial cortical plate with subsequent gingival recession, dehiscence, or fenestration. With mandibular incisors, it could be lengthening of the clinical crown or resorption of the lingual cortical
plate.13 However, none of these problems was detected. Periodontal evaluation showed a healthy condition 2 years posttreatment (Fig 11). This favorable response probably occurred because the patient’s initial periodontal condition was good; attached gingivae and plaque control were adequate.25 Periodontally compromised patients might not have such a satisfactory result.26 Extraction of the mandibular third molars could be considered a controversial treatment decision. This  procedure was undertaken to allow distal movement of the mandibular teeth to correct the A-P relationship. It
could be argued that these teeth should have been maintained. However, as a mandibular superimposition demonstrated (not shown), extraction of the third molars allowed the second molars to tip distally, facilitating A-P correction, even though the tipping was not considerable. However, the maxillary third molars are out of occlusion and could extrude. This problem can be overcome by splinting them to the second molars.27 In addition, extraction of the third molars helped control the vertical dimension in a patient who had a clinically long face.28 An alternative and more common procedure would be to extract the mandibular first premolars.29 Nevertheless, because the first molars were already absent, it was believed that space closure would be more difficult, especially on the right side where the second premolar and second molar roots were divergent.