Finite-element morphometry of soft tissues in prepubertal Korean and European–Americans with Class III malocclusions

The purpose was to test the hypothesis that soft-tissue morphology differs consistently in people of diverse ethnic origin exhibiting Class III malocclusions. Lateral cephalographs of 70 Korean and 71 European–American children aged between 5 and 11 years were traced and 12 homologous, soft-tissue landmarks digitized. The total sample was subdivided into seven age- and sex-matched groups, and Procrustes superimposition was used to generate average geometries scaled to an equivalent size. Statistical differences were tested by ANOVA. Graphical analysis using a colour-coded finite-element (FEM) program was used to localize differences in morphology. Procrustes’ results indicated that the overall mean Korean and European–American soft-tissue configurations differed statistically (p<0.001), and this difference was also true in all seven age groups tested (p<0.001). On comparing mean Korean and European–American Class III soft-tissue configurations for local size change, FEM analysis revealed that whereas the Korean mental regions generally were smaller (approx. 43% on average), local increases in size were apparent for the lower lip (approx. 29% on average). For shape change, the mean Korean and European–American soft-tissue configurations were fairly isotropic except in the region of the columella, lower lip and the anterior part of the mental region. Features of the soft-tissue integument in individuals of diverse ethnic origins appear to be associated with the underlying skeletal Class III morphology.