Comparison of transverse dental axis changes in skeletal class III with asymmetry treated by preorthodontic orthognathic surgery and conventional surgery

Abstract

The aim of this study was to evaluate, using 3D-CT, transverse dental axis changes in skeletal Class III patients with facial asymmetry who received 2-jaw surgery, and compare the changes between two different orthognathic surgery protocols; conventional surgery and preorthodontic orthognathic surgery. Total 29 skeletal Class III patients (15 men, 14 women) with asymmetry (menton deviation > 4 mm) were selected. Sixteen patients (CS group, 10 men, 6 women, mean age 21.8 ± 2.2 yrs) received conventional orthognathic surgery, and thirteen patients (POGS group, 5 men, 8 women, mean age 21.0 ± 1.7 yrs) received preorthodontic orthognathic surgery. Orthognathic surgery was proceeded with maxillary Le Fort I osteotomy and mandibular bilateral intraoral vertical ramus osteotomy (B-IVRO). Facial 3D-CT was taken before treatment (T0), 1 month before surgery (T1), 3 days after surgery (T2) and 1 year after surgery (T3). Skeletal and dental variables were measured and compared the dental axis changes between CS and POGS groups. The results are as followings,

1. By pre-surgical orthodontic treatment in CS group, upper 1st molar and canine had shown tendency of uprighting, but there was no significant difference between CS and POGS group at 1 month before surgery (T1).

2. In POGS group, lower canine of non-deviated side and upper 1st molar of both side inclined lingually by post-surgical orthodontic treatment (T2-T3).

3. One year after the surgery (T3), skeletal and dental measurements were similar between CS and POGS groups. However, there was significant difference of buccolingual inclination of maxillary and mandibular molars between deviated and non-deviated side in POGS group.

4.Although in CS group the pre-surgical orthodontic treatment (T0-T1) was done for about 12 months, total changes of buccolingual inclination of canine and molar showed no significant difference between CS and POGS groups (T0-T3).

Preorthodontic orthognathic surgery can be an efficient method for skeletal Class III patients with facial asymmetry in the aspect of shorter treatment time and immediate improvement of facial esthetics, and lead to almost the same treatment outcome comparing to conventional surgery. However, if there is severe difference of buccolingual inclination between deviated and non-deviated posterior teeth, conventional surgery with dental decompensation prior to orthognathic surgery would be a better surgical option for a relatively stable treatment outcome.