| Purpose. To measure the change in the proximal segment of the mandible after BSSO for mandibular advancement. A second purpose is to determine if the amount of movement of the proximal segment can be correlated to the relapse potential in patients.;Results. A difference was found for MPA, SNB, facial angle, gonial angle, mid-ramus point and advancement between the time periods. The mean change in mid-ramus point was 3.7 +/- 1.5 mm (TI-T2) and -1.5 +/- 0.9 mm (T2-T3). The mean change in advancement was 6.0 +/- 2.1 mm (T1-T2) and -2.1 +/- 1.1 mm (T2-T3). The correlation of the mid-ramus point and amount of advancement was r=0.42 (T1-T2) and r=0.57 (T2-T3).;Conclusions. Statistically significant changes occurred in the sagittal position of the proximal segment at mid-ramus point as the mandible was advanced (T1-T2) and relapsed (T2-T3). There was also a statistically significant correlation in the movement of the proximal segment as the mandible was advanced and relapsed. Thus, movement of the proximal segment does occur when the mandible is advanced and there is a positive correlation of this movement with the amount of advancement and relapse.;Methods. A Retrospective study of 35 patients (12 males, 23 females) who under went bilateral sagittal split ramus osteotomy (BSSRO) advancement with rigid internal fixation (RIF). Lateral cephalograms obtained preoperatively (T1), early postoperatively (T2), and after orthodontic treatment (T3) were used to assess: 7 angular (MPA, SNA, SNB, IMPA, facial angle, gonial angle, and articular angle) and 2 linear measurements (change in the proximal segment at mid-ramus point and amount of advancement at pogonion). A repeated measures ANOVA was used and then a least squared means comparison was used to determine the significant differences in parameters between the three different time periods and subgroups. Correlations between variables were obtained using the Spearman correlation procedure. |
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