[A FEM study for the biomechanical comparison of labial and palatal force application on the upper incisors. Finite element method].

The present study was designed to compare the biomechanical response of upper incisors to labial and lingual force applications. A three-dimensional finite element model was developed to analyze tooth displacement and stress distribution in the periodontal ligament. Lingually and apically directed forces of 1 N were applied at one point on the labial and at three points on the lingual surface of the crown. Tooth displacement and stress distribution resulting from lingual force applications were compared with those from the labial side. The following results were obtained: 1. Lingual horizontal forces produced similar patterns of tooth displacement and stress distribution, irrespective of the point of application (labial--lingual). 2. Apically directed vertical forces applied at the lingual points produced more uniform tooth displacements and stress distributions, although the force applied on the lingual side close to the CEJ, which happened to be most distant from the tooth's long axis, generated a pattern of movement somewhat different from the remaining two lingual force applications. The present results suggest the crucial role of the positional relation between the long axis of the tooth, respectively the center of resistance, and the point of force application. It can be deduced that lingual force application may produce more optimal tooth movement in terms of intrusion and subsequent stress distributions in the periodontal ligament.