Accelerated decompensation of mandibular incisors in surgical skeletal class III patients by using augmented corticotomy: a preliminary study.

INTRODUCTION: Our objectives were to evaluate the amount of decompensation of the mandibular incisors and the change of periodontal support around them after corticotomy with bone augmentation before orthognathic surgery.

METHODS: Before orthognathic surgery for 15 skeletal Class III patients, orthodontic treatment was combined with corticotomy and bone augmentation labially to the anterior mandibular roots. Lateral cephalograms were taken before orthodontic treatment and before surgery (completion of preoperative orthodontic treatment). The amounts of mandibular incisor proclination, alveolar bone thickness, and periodontal support (gingival margin levels and augmentation pattern) were evaluated.

RESULTS: Significant proclination of the mandibular incisors was shown after decompensation (P <0.001; incisor mandibular plane angle, 10.45°; incisor symphyseal plane angle, 10.74°). The incisor edge moved labially by 3.47 mm. The alveolar bone thickness increased by 1.56 mm at the root apex and 1.98 mm at the level of B-point (P <0.001). There was no gingival recession irrespective of the degree of proclination of the mandibular incisiors. Two types of bone augmentation pattern were evident. One was characterized by alveolar bone proclination proportional to the labial tipping of the mandibular incisors. Buccal alveolar bone at the cervical area was well maintained (60%, 9 subjects). The other showed greater increases in alveolar thickness at B-point than at the cervical area (40%, 6 subjects).

CONCLUSIONS: The augmented corticotomy provided effective decompensation of the mandibular incisors in skeletal Class III patients while maintaining labial bone thickness and with no periodontal side effects. This technique reduces or eliminates the risk of moving the roots through the labial plate during decompensation with the associated risk of gingival recession.