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Short lower anterior face height: phenotypic diversity

Introduction: Individuals with short lower anterior facial height (LAFH), reduced mandibular plane angle, and excessive overbite resulting from upward and forward mandibular rotation are traditionally classified as skeletal deep bites. Our purpose was to explore phenotypic variation within short LAFH individuals using geometric morphometric methods. Methods: Cephalograms of 101 individuals (64 female, 37 male; age range: 7-62 years) with LAFH to total anterior facial height (TAFH), ratio (LAFH/TAFH), at or below 52.6% were studied. Principal component analysis, cluster analysis, and canonical variate analysis captured phenotypic variation and identified homogenous groups. Results: Four principal components were identified which accounted for 49% of the variation within the skeletal vertical and sagittal dimensions, flexure of the gonial angle, and incisor angulation. Cluster analysis resulted in 3 discrete short LAFH subpenotypes. Conclusions: Within the selected population of short LAFH individuals, we found: A range of morphologic variation. Convergent and divergent facial patterns with concomitant variation in gonial angle and ramus height. Anteriorly directed condylar morphology correlated with characteristics of extreme forward mandibular rotation; less anteriorly directed condylar morphology correlated with characteristics of backward mandibular rotation. Overbite magnitude is independent of vertical skeletal relationship and/or characteristics of forward mandibular rotation.