GEOMETRIC MORPHOMETRICS CLUSTERS CRANIOFACIAL MORPHOLOGY DIFFERENTLY THAN TRADITIONAL CEPHALOMETRIC MEASUREMENTS

Abstract

Objectives: The purpose of the study was to compare a geometric morphometric approach for grouping different skeletal malocclusions to a traditional cephalometric approach for a subject population undergoing orthognathic surgery for treatment of malocclusion. Methods: Traditional cephalometric measurements were used to diagnose the skeletal malocclusion each subject in both the sagittal (SNA, SNB, ANB, Facial Angle) and vertical dimensions (SN-MP, FMA, Downs Y-Axis, Facial Axis, P-A Face Height). These were compared to skeletal diagnoses given by the treating surgeon. Lastly, geometric morphometrics was used to identify shape variance within the population, cluster homogeneous subsets, and identify variance between the clusters. Results: Traditional cephalometric analysis identified 21 Class II open, 18 Class II normal, 5 Class II deep, 3 Class I open, 4 Class I normal, 2 Class I deep, 2 Class III open, 4 Class III normal, 3 Class III deep. The surgeon identified 17 Class II open, 20 Class II normal, 13 Class II deep, 1 Class I open, 0 Class I normal, 0 Class I deep, 4 Class III open, 3 Class III normal, 4 Class III deep. Geometric morphometrics identified 6 clusters showing greatest variance through 1) vertical divergence, 2) sagittal positioning of the jaws, and 3) ramus height. Conclusion: Cephalometric analysis and a geometric morphometrics approaches to classification of malocclusion grouped subjects into distinct populations. However, the groupings did not agree between the two approaches.