Characteristics of posed smiles for class III female patients before and after osteotomy using principal component analysis

The purpose of this study was to clarify characteristics of posed smiles for Class III female patients before and after orthognathic surgery. Just before retrusion surgery and the removal of fixation plates, 2 sets of posed smiles were recorded for 7 Class III female patients. As normal controls, 7 healthy female volunteers were also recorded. Using our video-based motion analyzing system, range images and 5×5 virtual grids projected onto the lips were recorded for all patients while making a posed smile. The gravity for each area in the lips was calculated from the intersections of the virtual grids. Principal component analysis was applied to the normalized virtual grids, that is, a homologous model of lip shape, for all frames of the posed smiles. While the sample size was too small to generalize from these results, we found that the upper vermilion shifted posteriorly and laterally in posed smiles for Class III female patients after retrusion surgery as compared with the preoperative posed smiles. In addition, the characteristic lip movements during postoperative posed smiles for Class III female patients did not resemble those of the normal controls.