True vertical changes in patients with skeletal class III malocclusion after nonsurgical orthodontic treatment-a retrospective study comparing different vertical facial patterns.

BACKGROUND/PURPOSE: Rotating mandible backward downward is one of the treatment options in non-surgical skeletal class III malocclusion. The purpose of this study was to compare the true vertical changes after camouflage orthodontic treatment of adult patients with skeletal class III malocclusion categorized by vertical facial type.

MATERIALS AND METHODS

This retrospective study included 27 adult patients (age >18 years) with skeletal class III malocclusion (ANB<1°) who underwent nonsurgical orthodontic treatment at Taipei Veterans General Hospital. The patients were divided into the low-angle (SN-MP<28°), high-angle (SN-MP>36°), and normal-angle (28°≤ SN-MP ≤ 36°) groups according to the original vertical facial pattern. Pretreatment (T1) and post-treatment (T2) lateral cephalograms were superimposed and treatment changes were evaluated.

RESULTS

In all cases, proper overjet and occlusion were achieved after treatment, and the lower anterior facial height increased with the backward rotation of the mandibular plane. Increase in vertical dimension was the most obvious in the high-angle group, while it was the least obvious in the low-angle group. Extrusion of both the maxillary and mandibular incisors was observed in the high-angle group; however, intrusion of the maxillary and mandibular incisors and decreased overbite were observed in the low-angle group.

CONCLUSION

Camouflage orthodontic treatment of skeletal class III malocclusion improves the facial profile by increasing the vertical dimension and clockwise rotation of the mandible. According to our results, patients with a high mandibular plane angle showed better response to vertical dimension increment treatment mechanics than those with low and normal mandibular plane angles.