Biomechanical Study And Epidemiological Investigation Of Temporomandibular Joint With Large Mouth Opening

Part one:Epidemiological investigation between ways of opening mouth too much and temporomandibular disorders in college freshmenThe aim of this study is to investigate prevalence of temporomandibular disorders(TMD)among college freshmen and to explore effects of two different ways of much opening mouth wide on temporomandibular disorders. After standard conformance check, the examiner conducts special examination of temporomandibular disorders among 2625 college freshmen from Ocean University of China using double blind method and makes statistical analysis of the results by SPSS17.0. In our results, the prevalence rate of TMD is 23.6% in 2625 freshmen; 627 freshmen whose condylar process can be over articular tubercle(subluxation) represent 23.9% of the total number, including 266 TMD patients with the prevalence rate of 42.4%; while 1998 freshmen whose condylar process cannot be over articular tubercle(without dislocation) represent 76.1% of the total number,including 353 TMD patients with the prevalence rate of 17.7%; the difference of prevalence rates of two groups of freshmen is statistically significant(P<0.01). In conclusions, the prevalence rate of TMD in freshmen with subluxation with mouth wide open is significantly higher than that in freshmen without dislocation with mouth wide open, which indicates that the process of condylar process being over articular tubercle with moth wide open may cause overstimulation to joint structure and induce temporomandibular disorders.Part two:Mechanical Analysis on Individualized Finite Element of Temporal-mandibular Joint under Overlarge Jaw opening Status[Purpose] Analyze the stress status of temporal-manidbular joint(TMJ) of a healthy volunteer under the overlarge jaw opening status through the finite element method, with the purpose of clarifying the loading features of each structure in the joint area, and achieving further understanding of the pathogenesis and pathology of the temporomandibular disorders(TMD).[Method] Collect the cone beam CT and MRI image data of a volunteer respectively under the maximum jaw opening, extract the bone tissue data of CT image, and articular disc and other soft tissue data of MRI image, establish the finite element model of TMJ under the maximum jaw opening status through a series of software, image segmentation,rectification, meshing, material evaluation and other related processing, simulate the mechanical environment of this joint area under this status, and analyze the stress status of the articular disc, condyle cartilage, and condyle process.[Result] Through comparison on three structures, each stress generated by the articular disc is maximal, followed by the condyle process. The condylar cartilage is the smallest.The largest stress of the Von Mises of the articular disc is mainly focused on the anterolateral side of the articular disc, with the maximum value of 0.8852 Mpa. The distribution of three kinds of stress above and below the articular disc does not have obvious difference. The stress distribution of three kinds of stresses on the surface of condyle process and condylar cartilage is almost corresponding, but the stress of the condylar cartilage is generally less than the condyle process.[Conclusion] This research result reminds us that the normal people’s articular disc are easy to generate stress concentration under large jaw opening, but its stress is far less than the one under the biting status, and it does not cause TMJ lesion due to the overlarge stress. Besides, the TMJ symptom induced under the large jaw opening status is mainly caused by the displacement of the tissues, such as articular disc, etc. Under the large jaw opening status, the condylar cartilage plays a vital role in dispersing the stress. This method can be applied for carrying out individualized mechanical analysis on the patients with TMJ.