Verification and evaluation on induction scheme for bodily movement of incisor in children / 医用生物力学

Objective In order to analyze and evaluate the feasibility and effectiveness of induction scheme for bodily movement of incisor in children, the size, orientation and position of the force on tooth surface were estimated and analyzed. Methods The orthodontic jaw from a child was scanned to establish the 3D solid model including mandibular incisor, periodontal ligament and alveolar. Initial strain distributions on outer surface of the periodontal ligament were calculated by software Abaqus, and then the positive strain as the stimulation of the tooth movement was used to simulate the inducted effects from the inducer which was changed twice in succession. Results The rate of orthodontic tooth movement was about 0.27 mm per week, and the total displacement during an induction period was about 1 mm per month, showing it was in accordance with the real inducted effects in clinic. Conclusions The present study proved the feasibility of induction scheme for bodily movement of incisor in children and provided reference for formulation and optimization of induction scheme in clinic.

THE THREE DIMENSIONAL STRESS ANALYSIS ON VARIOUS DIRECTIONS OF THE MANDIBULAR CONDYLE MOVEMENT BY USING FINITE ELEMENT METHOD

The condyle head of mandible was usually influenced by the stressful forces generated from a voluntary movement of bone fragment after the sagittal ramus osteotomy which would be mainly performed for the mandibular deformity patient. In this study we measured the stress values exerted on condyle and evaluated which area of condyle had a more stress concentration while condyle head moved in X, Y and Z axis by using a 3 dimensional finite element model. The result were as follows: 1. On bodily movement, the value of maximum force was 40.98Kg/cm2 at the (-X) direction and the stress area was the center of superiposterior nonaticular area of the condyle. 2. On ratational movement, the value of maximum force was 173.1Kg/cm2 at the (+Y) direction and the stress area was the anterior area of condyle neck. 3. From the general point of view there were more stress on rotational movement than on bodily movement. 4. The stress concentration area was the condyle head on bodily movement and the condyle neck on ratational movement. 5. From the result of this study. We found out that this results were a correspondence with clinical predictions in which a condyle head got the most stress concentration only when a condyle head in the posterior rotational position during orthognathic surgery. 6. The results of this study show that we should consider not to place the condyle head in the posterior position and posterior rotational position during orthognathic surgery.