An evaluation of the biomechanical response of the tooth and periodontium to orthodontic forces in adolescent and adult subjects.

This study was designed to quantify the magnitude of tooth mobility in adolescents and adults, and to investigate the differences in the biomechanical response of tooth and periodontium to orthodontic forces. The initial displacement of the maxillary central incisor was measured in 50 adolescent and fifty adult patients and the biomechanical properties of the periodontium were examined using the finite element method (FEM) and supporting experimental data. The magnitude of tooth mobility was significantly greater in the adolescent group than in the adult group. By integrating the differences in tooth mobility in both subject groups with analytical tooth displacements, the Young's modulus of the periodontal ligament (PDL) was demonstrated to be greater in the adults than in the adolescent subjects. The differing biomechanical properties of the PDL in adults were demonstrated to result in almost equivalent or somewhat increased stress levels in the PDL in adult subjects. It is suggested that this might produce a reduction in the biological response of the PDL and thus lead to a delay in tooth movement in adults.