Soft tissue thin-plate spline analysis of pre-pubertal Korean and European-Americans with untreated Angle's Class III malocclusions

The purpose of this study was to assess soft tissue facial matrices in subj ects of diverse ethnic origins with underlying dentoskeletal malocclusions. Pre-treatment lateral cephalographs of 71 Korean and 70 European-American children aged between 5 and 11 years with Angle's Class III malocclusions w ere traced, and 12 homologous, soft tissue landmarks digitized. Comparing, mean Korean and European-American Class III soft tissue profiles, Procruste s analysis established statistical difference (P < 0.001) between the confi gurations, and this difference was also true at all seven age groups tested (P < 0.001). Comparing the overall European-American and Korean transforma tion, thin-plate spline analysis indicated that both affine and non-affine transformations contribute towards the total spline (deformation) of the av eraged Class III soft tissue configurations. For non-affine transformations , partial warp (PW) 8 had the highest magnitude, indicating large-scale def ormations visualized as labio-mental protrusion, predominantly. In addition , PW9, PW4, and PW5 also had high magnitudes, demonstrating labio-mental ve rtical compression and antero-posterior compression of the lower labio-ment al soft tissues. Thus, Korean children with Class III malocclusions demonst rate antero-posterior and vertical deformations of the labio-mental soft ti ssue complex with respect to their European-American counterparts. Morpholo gical heterogeneity of the soft tissue integument in subjects of diverse et hnic origin may obscure the underlying skeletal morphology, but the soft ti ssue integument appears to have minimal ontogenetic association with Class III malocclusions.