Construction of a 3D digital virtual model mostly depends on microscopic slice images of a cadaveric specimen, and hence, research in this field is limited to a few large research institutions with low-temperature and ultra-thin milling equipment; this hinders development and application of digital medicine into clinical practice. In addition, use of ultra-thin sections of corpse modelling has the following disadvantages: first, anatomical specimens can only be sliced in a single direction, while imaging equipment can collect information in multiple directions. Second, information from cadaveric specimens collected by anatomical sections is different from that of living organisms.
Cornelia Kober et al. [11,12] reconstructed the articular fossa and condyle by using MRI data and realised the visualisation of TMJ system by combining original 2D images of the articular disc with MRI images. CT and MRI have their own advantages in imaging; certain scholars have established a complete TMJ system by modelling these two types of scanning data separately and by using fusion registration to form a complete TMJ system [13–16].
In this study, TMJ was scanned using high-resolution CT and MRI in vivo. Advantages of CT and MRI were used to establish the joint fossa, maxilla and mandible, which included the articular fossa, maxilla and mandible. A 3D digital model of the entire dentition and the articular disc was created. All masticatory muscles, ligaments and adhesions in TMJ were simulated.
The disc is located between the condyle and the temporal bone. It functions as a cushion for stress in the joint. Diseases of TMJ affect stress distribution and interactions between structures in the TMJ to a certain extent, which has a negative impact on the structure and function of the joint. In this study, stress of the normal disc was concentrated in the lateral part of the middle band, and stress distribution was more uniform. However, when anterior displacement of the joint disc occurred, stress concentration was noted in the middle band of the joint disc. Such high stresses tend to lead to thinning or perforation of the joint disc. Tanaka et al. also reported that anterior displacement of the disc resulted in increase of compressive and shear stresses of the articular disc during median occlusion, which could easily cause disc thinning and perforation Moreover, P é rez-Palomar et al.  conducted a finite element study of the TMJ system with anterior disc displacement and found that the pressure and shear force in the posterior disc zone after anterior disc displacement of TMJ were higher than those observed in normal TMJs.
The articular capsule is lined by the synovium, and the sub-intimal layer is rich in blood vessels. The joint fluid is secreted from the synovium into the articular cavity and contains numerous immune cells, proteins, mucin, and so on. It primarily provides a liquid environment for the articular surface and functions as a lubricating agent. By changing the friction coefficient of the disc of the affected side, we observed peak stress changes of the disc, condyle and mandible and found that when the friction coefficient of the disc of the displaced side increased, the disc of the corresponding side could be observed. Stress in the condyle and mandible was also increased. Simultaneously, stress values of the disc, condyle and mandible were higher than those of normal joints. Mongini et al. believed that anterior disc displacement may result in flattening of the anterior oblique plane of the condyle, which is consistent with our findings that increase of the friction coefficient after anterior displacement of the articular disc leads to increase in stress on the anterior oblique plane of the condyle. Dijgraaf et al.  demonstrated that joint lesions were related to the position of the articular disc. NitZna et al. showed that TMJ lesions were related to abnormal position of the articular disc and increase of friction coefficient; this study further proved that TMJ disease is closely related to its stress distribution. Hence, prevention and treatment of TMJ disease can be achieved by maintaining interactions among structures in normal TMJ.