Heritability of facial proportions and soft-tissue profile characteristics in Turkish Anatolian siblings

Introduction: The purpose of this study was to determine the possible effects of genetic factors on facial proportions and soft-tissue profile characteristics in Turkish Anatolian siblings. Methods: The material consisted of lateral and posteroanterior cephalometric head radiographs of 138 siblings (70 women, 68 men) living 15 years or more in the province of Erzurum in eastern Turkey. The subjects were required to have completed their pubertal growth spurts and to have received no previous orthodontic or prosthodontic treatment. The heritability assessments of craniofacial and soft-tissue measurements were undertaken according to narrow-sense heritability. For the calculation and evaluation of heritability estimate values, the mixed-model least-squared and maximum likelihood computer program model type II was used for statistical analysis. Results: According to the narrow-sense heritability estimate values, the measurements of total depth index, soft-tissue chin thickness, soft-tissue facial angle, Merrifield angle, and Holdaway angle showed the highest heritability coefficients (P <.001). Total height index, anterior height index, facial width index, upper to lower facial height index, and lower lip-E line measurements demonstrated moderate heritability values (P <.01). The upper depth index had a low but statistically significant heritability value (P <.05). However, no statistically significant heritability coefficient in upper lip-E line measurement was found. Conclusions: Turkish Anatolian siblings have similar facial features regarding facial proportions and soft-tissue measurements.