The relationship between mandibular morphology and apical root curvature in man.

Two samples of individuals, a low-angle group and a high-angle group, were selected on the basis of the inclination of the lower border of their mandible, defined by the mandibular plane angle (ML/SNL) in profile radiographs. Apical root curvature of mandibular first and second premolars and molars on panoramic radiographs was compared between the two groups and related to mandibular morphology. In the low-angle group most teeth had more distally curved roots than in the high-angle group. Significant differences were found for the first premolars on both sides (p less than 0.001, p less than 0.05), the right second premolars (p less than 0.05) and the distal root of left first molars (p less than 0.05). Correlations were calculated between root curvature and two variables reflecting mandibular morphology, the mandibular plane angle and the gonial angle. The strongest associations were found between the first premolar roots and the gonial angle (rs = -0.75, p less than 0.001 and rs = -0.56, p less than 0.01, for right and left sides respectively). The association between mandibular morphology and root curvature is probably indirect, caused by tooth migration during root formation.