Abstract
The purpose of the study was to use the finite element method to investigate the stress related changes in periodontal ligament of the posterior segment under orthodontic force application. The three dimensional finite element models of the maxillary first molar, maxillary first premolar, bracket,arch wire and molar tube are constructed. The models of the tooth were made from CT scans of the natural tooth. Dimensions of the tooth were taken from the Wheeler's text book. Mechanical parameters of PDL, root, alveolar bone and stainless steel wire were included. Two different directions of forces, mesial and distal were used in five different amounts, 250 g, 300 g, 350 g, 400 g, 450 g. Uneven distributions of the compressive and tensile stresses were seen in the PDL. This was due to the tendency of the teeth to rotate and tip instead of undergoing bodily movement.