Cheek configuration during smile in Class III patients

Objectives:

The purpose of this study was to investigate the difference of the changes in cheek surface configuration between normal and skeletal class III subjects.

Methods:

Two groups consisted of Japanese female subjects were selected for the study. A group of eight skeletal Class III patients (Mean age, 20y0m; Class III Group) who were diagnosed as requiring orthognathic surgery and a group of fifteen healthy subjects with normal jaw relationships (Mean age, 20y1m; Control Group) were considered. The subjects performed two types of facial expressions, i.e. Rest and Portrait smile. Three-dimensional facial images were recorded for each subject by means of a 3D-digitizer (Danae100SP, NEC Engineering Ltd., Tokyo). We measured surface configuration of the cheeks in the upper and lower portions, i.e. the Ear-Lip contour and the Eye-Lip contour. The standardized amount of changes in length (Cheek-base Length) and thickness of the cheek (Cheek Prominence) for the Ear-Lip and the Eye-Lip contours between the Rest and the Portrait smile were calculated using 3D shape analyzing software (3D-Rugle ver4, Medic Engineering, Kyoto). Mann-Whitney tests were employed to compare the changes in Cheek-base Length and the Cheek Prominence between the two groups with the pooled data set of the left and right sides. P values > 0.05 were assigned not significant.

Results:

The standardized amount of changes of the Cheek-base Length and the Cheek Prominence for the Eye-Lip contour in the Class III Group were smaller than those in the Control Group (p=0.011 and P=0.037, respectively).

Conclusion:

The present study showed significantly smaller amount of changes for the Eye-Lip contour in the Class III Group, suggests the changes in cheek surface configuration were different between the skeletal jaw relationships.