Variability of the dental surface: effects on orthodontic treatment.

Objectives: The Author studied the variability of the vestibular surfaces of tooth usually involved in orthodontic treatment.
Materials and Methods: 200 model casts of Italian subject with complete permanent dentition have been analyzed studying the clinical crown dimension and the angulations of tangents drawn at 3 and 4 mm.
Results: The authors found differences in the vestibular surfaces curvature in the last teeth of each series, more accemptuated in the lower than in the upper arch.
Conclusion: The conclusions of this study are related to the use of orthodontic straight wire appliances. The use of standard values with a complete torque, independently from the individuals, is based on the hypothesis of equal positioning on the tooth surface and related to the teeth axis. A variation in the torque of the upper central incisor for different kinds of straight wire appliance related to extreme variation of vestibular curvature is hypothesised.