The relationship of handedness to asymmetry in the occlusal morphology of first permanent molars.

Handedness has been shown to be related to a number of systematic asymmetries in body dimensions, dermatoglyphic patterns and cerebral morphology. The aim here was to compare linear and angular tooth crown asymmetries of the permanent molars in healthy right-handed and left-handed subjects. The material comprised 27 children with recorded concordant left-side dominance of hand, eye and foot. The controls were an age- and sex-matched group with right side dominance. The material is based on the Collaborative Perinatal Project where detailed medical records and the dentitions, including accurate dental impressions, of over two thousand American children were examined in the USA in the sixties. Machine vision technique was used to obtain accurate three-dimensional information from the occlusal surfaces of the first permanent upper and lower molars. The directional asymmetry values of angular measurements of mandibular first molars showed evidence of asymmetry of opposite direction between the two examined groups. The results indicate that occlusal morphology of first permanent molars may be affected by handedness, and this tendency is most evident in the angular measurements of the mandibular molars. Fluctuating asymmetry did not differ significantly between the examined groups.