Long lower anterior face height: phenotypic diversity

Introduction: The hyperdivergent facial form is typically characterized by a long lower anterior facial height (LAFH), steep mandibular plane angle, and skeletal open bite. The purpose of our study was to further explore morphologic variation within long LAFH subjects using geometric morphometric methods. Methods: Cephalograms of 147 individuals (n= 147; 87 female, 60 male; age range: 16-68 years) with LAFH to total anterior facial height (TAFH), ratio (LAFH/TAFH), at or above 57.4% were studied. Cluster analysis and canonical variate analysis captured phenotypic variation and identified homogenous groups. Results: Cluster analysis resulted in three discrete long LAFH phenotypes that varied along vertical and anteroposterior dimensions. Conclusions: We found significant morphologic variation within the sample population of long LAFH individuals. Three phenotypes with varied vertical and anteroposterior discrepancies were revealed through the cluster analysis. Within our sample, we found both convergent and divergent facial patterns with concomitant cranial base rotation and posterior ramal border displacement. Vertical variation was largely independent of anteroposterior discrepancies.