Three Dimensional Finite Element Analyses Of Maxillary Teeth Under Intermaxillary Elastics

Objective: To construct a three dimensional finite element model(3D FEM), including maxillary and upper teeth, for the analysis stress distribution and the displacement of the upper teeth with three kinds intermaxillary elastics respectively.Methods: A series of maxillary CT images of a healthy volunteer were collected, DICOM digital image transfer and transcription into MIMICS. 3D FEM of maxillary complex ,upper teeth, including the straight wire appliance(SWA) of 0.019×0.025 wire and brackets were used in combination MIMICS and PATRAN software. 50g, 100g, 150g, 200g, 250g and 300g was loaded respectively to simulate intermaxillary elastics. Stress and the displacement data about maxillary complex and the upper teeth were calculated by using MSC.NASTRAN.Results and Conclusion: 1 The 3D FEM of normal maxillary complex and upper teeth is constructed, including molar and anterior teeth roots, brackets and the corresponding appliance for the first time. It is of 33604 nodes and 24913 elements. The method to develop a model of maxillary complex and upper teeth is feasible and effective with the better simulation of the geometry and the biomechanics.2 Stress and the displacement analysis of upper teeth under intermaxillary elastics.2.1 ClassⅢelastics: The whole upper arch has been extruded forward and anterior teeth depressed while the upper first molar moved toward tongue and extruded. The anterior openbite'cause is that the upper anterior teeth depressed and molar extruded; It is necessary to widen the archwire under the ClassⅢelastic. Compare to long ClassⅢelastic, the displacements are little and the stress are greater when using short ClassⅢelastic. It presents that short ClassⅢelastic should not be applied for in the case of"High-angle"patients2.2 ClassⅡelastic: The about translation of the upper anterior teeth, the crown of the incisors inclined toward midline slightly, but the canine opposite. It also shows more force at the cervical level of the lingual root surface. The upper archwire should be strict. Compared to the long ClassⅡelastic,the displacement magnitude of the Z and the X direction is greater and the stress is less, but the backward value is similar . In the clinic practice, the short ClassⅡelastic should not be used in the"Excessive-overbite"patient.2.3 Anterior box elastics: The upper dentition fore width is shortened and the back extended slightly. In the clinics, potential change of the overjet between the upper and the low dentition should be given attention to. The max magnitude of max principal and the displacement is presented in the lateral incision in the three anterior teeth. It is clearly indicated that the lateral incision is benefited from the box elastic.2.4 The first molar up-down elastics: the upper arch moved down, extruded and the retral width of the...