[A primary construction of the 3D finite element model for fixed edgewise appliance].
OBJECTIVE
To construct a three-dimensional finite element model (3D-FEM) of the fixed appliance for mechanical analysis.


METHODS
The figures of the brackets and the edgewise wire were constructed at the platform of powerSHAPE3040, based on a male's figures of mandibular dentition and alveolar bone. First, the bracket slot center plane (H plane) was lined, which was 4.3mm under the mesial buccal cusp of the 2nd molar and parallel to the XY plane. The point that each tooth's axis of buccal surface (line A) crossed the H plane was at the bracket's center (point O). Second, on the basis of H plane, line A, and point O, 0.018 inchx0.025 inch brackets were constructed on the teeth. All the slots were on the H plane.Then, according to the brackets' slots, plane f was gotten, which went through every slot smoothly and was perpendicular to the XY plane. At the base of slots' basal wall and gingival wall, the 0.016 inchx0.022 inch wire was constructed on the plane f. The figures of edgewise wire, teeth, alveolar bone, and brackets were transferred to ANSYS5.5 system in the IGES format. The teeth, periodontal membrane (PDM), alveolar bone, and brackets were broken down to 4-node tetrahedron element. The 10-node tetrahedron element was chosen to make the model of edgewise wire.


RESULTS
The 3D-FEM of the brackets with teeth, PDM, alveolar, and the edgewise wire about the mandible were obtained. This kind of bracket was torqued slot bracket, which is similar to the preadjusted appliance. The edgewise wire was not as same as catenary curve or parabola completely. There were inset and offset on the wire following the dentition model. When the plain edgewise wire was inserted in the brackets, there was no force between the wire and brackets. If the wire was deformed as designed, the action could be analyzed.


CONCLUSIONS
3D mechanical analysis about the fixed appliance could be done on the model.
Yan
Yong-qing
YQ
Department of Stomatology, Ruijin Hospital, Shanghai Second Medical University, China. yanyongqing008@163.com
Yan
He-qing
HQ
Cai
Zhong
Z
Wang
Dong-mei
DM
Qian
Yu-fen
YF
Wang
Cheng-tao
CT
D020342:Finite Element Analysis; D006801:Humans; D008334:Mandible; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D010513:Periodontal Ligament; D014087:Tooth Movement Techniques