Finite Element Analysis Of The Effect Of Intermaxillary Traction On Stress Distribution And Displacement Of Temporomandibular Joint

Objective Through establishment of a complete craniomaxillofacial three-dimensional finite element model including the temporomandibular joint,the upper and lower jaws,the dentitions,and MBT straight wire appliance,simulates practical application of class Ⅱ intermaxillary traction and Ⅲ intermaxillary traction used in clinical practice,which are respectively loaded with six different force values for analysis of stress distribution and displacement changes at the temporomandibular joint area under 12 conditions as formed,so as to provide a reference for clinical choices of appropriate intermaxillary traction values.Methods Choose a healthy adult female volunteer as a sample,and CBCT scanning was performed on the sample,to obtain original dicom data.The data were imported into MIMICS 17.0,and three-dimensional reconstruction of teeth,upper and lower jaws,and joints were performed by orientation definition,two-dimensional mask edition,and three-dimensional reconstruction.And the data were imported into Geomagic Stutio12.0 for reverse processing.The models of the appliance and archwire were established with Siemens NX8.5 and assembled on the teeth.Corresponding Boolean operations were performed to obtain a complete threedimensional model.The model was then imported into Ansys Workbench 16.1,given with material properties of the teeth,jaws,joints,appliances,and archwires,applied with boundary conditions,and loaded with force values of 50 g,100g,150 g,200g,250 g,and 300 g,respectively.Calculations and processing were performed,to obtain the stress distribution and displacement trend of the condyle and the articular disc.Results 1.A complete craniomaxillofacial three-dimensional finite element model including the temporomandibular joint,the upper and lower jaws,the dentitions,and the BMT straight wire appliance is established.The model is complete in structure,reasonable in meshing,and had high mechanical similarity.It is possible to extract some parts from the model for further study as required.This provides a good foundation for the study of biomechanical changes in the temporomandibular joint caused by intermaxillary traction.2.During the class Ⅱ intermaxillary traction,with respect to stress,the first principal stress on the front slope of the condyle was compressive stress,and the back slope of the condyle was subjected to tensile stress.The outside of the front slope of the condyle near the condyle neck is a stress concentration area.The lateral of the anterior edge of the articular disc is stressed due to compression of the condyle.With respect to displacement,the condyle moved forward and downward,with the maximum displacement located on an inner side of the back slope of the condyle.The displacement trend of the articular disc was consistent with that of the condyle.During the class Ⅲ intermaxillary traction,the front slope of the condyle was mainly subjected to tensile stress,and the first principal stress of the back slope was compressive stress.The maximum equivalent stress was located in an outside area of the junction between the front slope of the condyle and the neck of the condyle.The condyle moved backward and upward,and the movement direction of the articular disc was consistent with that of the condyle.Conclusions When use Ⅱ and Ⅲ intermaxillary traction,the greater the loading force,the greater the stress and displacement of the condyle and the joint disc in the range of 50 g ~ 300 g loading.