Morphology of the mandibular canal and the angulation between the mandibular and mental canals in dry skulls.

The aim of this study was to analyse the correlation between external and internal mandibular morphology in adult or adolescent normal anthropological mandibles. Lateral radiographs of 31 symmetrical mandibles were analysed. The external morphology was defined by the gonial and beta-angles. In order to analyse internal morphology, a metallic pin was placed in the mental canal on the left side before radiography. The angle between the mental and the mandibular canals was termed the 'mental angle' and that expressing the curvature of the mandibular canal, the 'mandibular angle'. Spearman correlation analysis was used to investigate the relationships between the angles. Internal morphology: a statistically significant correlation was found between the mental and mandibular angles (correlation coefficient: -0.60, P=0.0004). When the mental angle was narrow, the mandibular angle tended to be wide, while a wide mental angle was interrelated with a narrow mandibular angle. External morphology: a statistically significant correlation was found between the mandibular and gonial angles (correlation coefficient: 0.57, P=0.0009). A weaker correlation was also found between the mandibular and beta-angles. The findings show that the internal courses of the mandibular and mental canals are interrelated. They also indicated that the course and morphology of the mandibular canal are interrelated with external mandibular morphology.