The purpose of this study was to extract characteristic three-dimensional dentofacial changes during the retention period and to clarify morphological factors affecting the stability of postoperative occlusion in mandibular prognathic patients with open bite and asymmetry.
Seven adult patients having negative A-B difference and overbite in the pretreatment stage and more than 5 mm mandibular setback differences between right and left side were selected for this study. The subjects were divided into the following two groups; 3 subjects who underwent mandibular setback osteotomy with the sagittal split technique (one-jaw group) and 4 subjects who underwent mandibular setback osteotomy with the sagittal split technique and Le Fort I osteotomy (two-jaw group). The lateral and frontal cephalograms taken at three stages; pretreatment, posttreatment, and under retention (more than one year after posttreatment) were used for quantitative evaluation of dentofacial changes.
Changes in denture components, skeletal components, and anterior occlusion during the retention period were analyzed three-dimensionally, respectively. The results were as follows:
1. As for the anteroposterior dimension, there were some relapse in the skeletal components in both groups, and the amount of relapse in the one-jaw group was larger than in the two-jaw group. However, the overjet was stable because of compensatory changes in the denture componentssuch as labial tipping of the upper incisors and lingual tipping of the lower incisors.
2. As for the vertical dimension, the overbite in both groups decreased because of relapse in the skeletal and denture components.
3. As for the transeverse dimension, there was a little relapse in the skeletal components in both groups. However, the midline of anterior teeth was stable because of compensatory changes of the lower incisors. These results suggested that it is important to maintain long-term stability of the anterior occlusion in the vertical dimension in patients with three-dimensional dentofacial deformity.
