The purpose of this study was to analyze three-dimensional changes in soft tissue with those in hard tissue following mandibular setback surgery in skeletal Class III patients.
Materials and methods:
The subjects comprised 11 skeletal Class III patients who had undergone BSSRO for analyzing three-dimensional changes in soft tissue.
Materials consisted of two facial three-dimensional data, dental three-dimensional data and lateral cephalograms. According to the reconstruction system previously reported, we constructed three-dimensional integration data, and set reference frames and measuring lines. The measurement regions were six areas: the upper buccal, lower buccal, subnasal, upper lip, lower lip and chin areas. Then, we calculated changes in soft tissue, hard tissue and soft tissue thickness with orthognathic surgery. To determine the ratio of soft tissue change and thickness of soft tissue change to hard tissue change, linear regression analysis was calculated and the regression parameters, a1: amount of soft tissue change/amount of hard tissue change as soft tissue change ratio, a2: amount of thickness of soft tissue change/amount of hard tissue change as thickness of soft tissue change ratio, were examined.
Results:
The thickness of soft tissue increased in the lower lip, chin and lower buccal areas and decreased in the upper lip and upper buccal regions. The soft tissue change ratio was 0.13∼0.30 in the upper lip and upper buccal regions, and 0.6∼0.78 in the lower three regions. The coefficient of determination (R²) was 0.50∼0.65 in the lower three regions. The thickness of soft tissue change ratio was -0.21 to -0.03 and 0.20∼0.23 in the upper three regions and lower three regions respectively.
Conclusion:
Integration data of facial tissue and dentition are useful for statistical analysis of three-dimensional changes in soft tissue before and after mandibular setback surgery with high accuracy. The soft tissue change ratio in the lower four regions were similar to the results of other studies, although the reconstruction system and measurement methods were different.