Genetic influence on the curves of occlusion in children seeking orthodontic treatment

Abstract

To examine the proportion of variability in the Curve of Wilson (COW) and the Curve of Spee (COS) that is explained by genetic factors in siblings seeking orthodontic treatment. Pre-treatment cone-beam computed tomography (CBCT) of 148 sibling patients were selected. The sample consisted of 79 females and 69 males with a mean age of 12 years 7 months. The COS was measured by creating a tangent line from the distobuccal cusp of the mandibular first molars and the highest incisal tip of the mandibular incisors. Measurements were taken from that tangent line to the deepest point on the premolars and canines. The COW was measured using the molar axis line to the perpendicular to WALA (Will Andrews Lawrence Andrews) points' axis line. The results indicate that these occlusal curves are generally moderate to highly heritable. Heritability of COW-maxilla was 78.3%, heritability of COW-mandible was 43.2% and heritability of COS was 100% (P-value<0.05). Most of the developmental variability in the curves of occlusion comes from genetic differences, with very little contribution from environmental factors. Therefore, siblings tend to show similar occlusal curves.