Structural Associations Between Palatal Morphology and Upper Airway Dimensions: Genetic and Environmental Contributions From A Twin Study

OBJECTIVE: This study aimed to investigate the structural associations between palatal morphology and upper airway dimensions in twins with completed craniofacial growth, while evaluating genetic and environmental contributions. METHODS: The sample comprised 53 twin pairs (27 monozygotic, 26 dizygotic; mean age 17.8 years). Palatal parameters were obtained from digital 3D casts, and upper airway dimensions were assessed using lateral cephalograms. Pearson correlation analysis was performed, and multiple comparisons were controlled using the Benjamini-Hochberg false discovery rate procedure. Heritability estimates were derived using structural equation modelling within the classical twin design (ACE model). RESULTS: Interpremolar and intermolar widths were positively correlated with the PCV-AH distance (posterior cervical vertebra to anterior hyoid) (r = 0.27-0.43, p ≤ 0.005), representing the sagittal distance between the posterior pharyngeal wall and the anterior hyoid bone. Palatal surface area (r = 0.30, p ≤ 0.003) and palatal volume (r = 0.29, p ≤ 0.003) were also associated with PCV-AH. Palatal height showed moderate correlations with PCV-AH (r = 0.29-0.30). CONCLUSION: Several palatal parameters were significantly associated with the PCV-AH distance, a measure showing substantial shared environmental influence. The environmental predominance of this airway parameter suggests functional plasticity within the maxilla-hypopharyngeal relationship. These findings indicate that structural maxillary characteristics may interact with environmental or functional factors and may be responsive to environmental or functional influences.