Stability Study of Total Temporomandibular Joint Replacement on Sheep

Objective: To evaluate the stability of our custom-made prosthesis by establishing the model of sheep total temporomandibular joint (TMJ) replacement.

Methods: Six sheep were included in our study. Spiral computed tomography (CT) data of all sheep was obtained and transformed into 3-dimensional model by surgicase5.0 software preoperatively. Total TMJ prostheses were made based on the skull model. Ultra-high molecular weight polyethylene was used to make glenoid fossa lining, while titanium alloy to prefabricate mandibular retention handle and titanium plate over glenoid fossa. Cobalt-chromium-molybdenum alloy was also used to prefabricate the condyle. The right sides of all sheep, as the experimental group, were carried out total TMJ replacement, while the left sides were as the control group. The bone in both experimental and control side were excised after 3 and 6 months. Scanning electron microscope (SEM) was used to observe the interface between bone and prosthesis. Van Gieson staining and immunohistochemical staining (IHC) were used respectively to observe the interface of titanium screw and bone and the expression of alkaline phosphatase (ALP).

Results: SEM and Van Gieson staining showed that there was immature bone and osteoid formed in the interface of prosthesis and bone after 3 months. While after 6 months, there was osseointegration between them. IHC showed that the expression of ALP in the experimental side was much higher than in the control side after 3 months and its expression decreased after 6 months with no difference from the control side.

Conclusion: The custom-made TMJ prosthesis which was designed and manufactured by ourselves has good stability after total TMJ replacement.