Three biologic variables modifying faciolingual tooth angulation by straight-wire appliances.

The facial surface contours of 600 maxillary and mandibular teeth, including 50 of each type of tooth from central incisors to first molars, were measured. Facial contours present at the same location, facial contours from occlusal/incisal to gingival surfaces and the angle formed by the coronal and radicular long axes varied among teeth of the same type. The magnitude of the variation found was so great as to suggest that differences between patients or differences in height of bracket placement are greater than the differences between the standard torque prescriptions now used in orthodontics. No single point, including the coronal midpoint (LA point), was found to be constant among teeth of the same type. Variation in facial surface contour tended to be greater in the posterior teeth than in the anterior teeth. Future custom construction of brackets, adjusted to individual facial contour differences, will also require information regarding optimal tooth position in the head, including compensations necessary for variations in facial skeletal pattern.