Evaluation of stress changes in the mandible with a fixed functional appliance: a finite element study.

INTRODUCTION: The aim of this study was to evaluate the effects of a fixed functional appliance (Forsus Fatigue Resistant Device; 3M Unitek, Monrovia, Calif) on the mandible with 3-dimensional finite element stress analysis.

METHODS: A 3-dimensional finite element model of the mandible was constructed from the images generated by cone-beam computed tomography of a patient undergoing fixed orthodontic treatment. The changes were studied with the finite element method, in the form of highest von Mises stress and maximum principal stress regions.

RESULTS: More areas of stress were seen in the model of the mandible with the Forsus compared with the model of the mandible in the resting stage.

CONCLUSIONS: This fixed functional appliance studied by finite element model analysis caused increases in the maximum principal stress and the von Mises stress in both the cortical bone and the condylar region of the mandible by more than 2 times.