Effects of root morphology on stress distribution at the root apex during orthodontic treatment

The stress distributions of two teeth with normal shape and bent root were compared. Two three-dimensional finite element models of the teeth with normal shape and bent root were established according to CT. The loads corresponding to bodily, tipping, and intruded movements were applied to the two models. The von Mises stresses on the roots and periodontal ligaments of the two models were compared. The results showed that the stress distributions of the two models were similar. The stresses in the two models were gradually increased from the root apexes to the alveolar crests under bodily and tipping movements. The maximum stresses in the two models were located at the distal root apexes under intruded movements. The stresses of the model with bent root were much higher than those of the model with normal shape. The maximum von Mises stress on the periodontal ligament with bent root was so high that could cause root resorption. It was concluded that because bent root could increase the stresses in the root and periodontal ligament, the special orthodontic therapy should be developed to treat the teeth with abnormal root morphologies.