How do environmental and genetic factors determine the anatomy of the palate. The relationship between the palate and upper airway

AIM: The aim of this study was to assess the relative contributions of genetic and environmental factors to variation in palatal parameters in twins with completed maxillary growth and to investigate a relationship between pharyngeal airway space and palatal measurements. MATERIALS AND METHODS: The study sample consisted of dental casts of 85 twin pairs of the same sex. Mean age 17.95±2.83 years. All study subjects had a DNA test to determine zygosity of the twins. All linear landmark-based dimensions were calculated using an open source universal 3D processing and animation software Blender. Genetic analysis and heritability estimation were performed using maximum likelihood genetic structural equation modelling (GSEM). The cephalometric analysis was used to measure airway and skeletal dimensions. RESULTS: The AIC values for each model were calculated The most parsimonious model and the lowest values were chosen. The AE and DE models were found to be the most parsimonious for variables. Variables with the best-fi tting model of the contribution of factors (a2, c2, d2, e2) were counted. A model with specifi c environmental factors (e ) and common environmental factors (c ) was rejected. Heritability estimates were high for all widths, maxillary depths, palatal surface areas and palatal volumes, ranging from 0.48 to 0.8. The palate area and volume were directly proportional to PCV – AH (r=0.28; p=0.002) and SPT (r=0.2; p=0.047). Intercanine distance at gum line and intercanine hight were correlated with ANS-AH angle (r=0.19; p=0.046); (r=0.26; p=0.007) respectively. CONCLUSIONS: Palatal parameters have high heritability and were found to be under strong additive genetic control. Variable PCV- AH is determined by the common environmental factors and it has direct relationship with palate surface. Intercanine distance is correlated with ANS – AH. Both parameters are determined by genes. These results can help plan orthodontic treatment in patients with breathing disorders.