OBJECTIVETo construct a three-dimensional finite element model of mandible and to analyze the stress distribution in mandible advanced with Forsus.

METHODSOne growing patient with mandibular retrusion was selected. After leveling and aligning with MBT (Mclaughlin Bennett Treriri) straight-wire appliance to achieve the request of forsus with the spiral CT, a three-dimensional finite element model was constructed and the stress distribution in mandible after advancing at 1 second, 15 seconds and 300 seconds was analyzed.

RESULTSThe three-dimensional finite element model included MBT straight-wire appliance. The stress concentration areas were located in the front side of the condylar process, the sigmoid notch and mandibular molar areas at 15 seconds and 300 seconds after mandibular advancement. The maximum stress values were 34.47 MPa and 34.45 MPa, respectively. With the extension of loading time, the largest displacement increased from 3.30 x 10(-2) mm to 1.15 mm and the region of the largest displacement extended backwards along the body of mandible. However, the displacement of condyle reduced from 1.65 x 10(-2) mm at 1 second to 3.27 x 10(-5) mm at 300 seconds after mandibular advancement.

CONCLUSIONSThe three-dimensional finite element model considered the viscoelasticity and viscoelasticity of mandibular. The result suggested that the stress distribution in the mandible gradually became stable after the application of Forsus and the appliance caused downward and forward mandibular modification.