Methods: In our study, stress distribution on the TMJ condylar cartilage surface was evaluated using a finite element model, whose construction was based on the computer tomography (CT) scans of the skull of a 6-month-old goat at the 4th week after completion of right mandible distraction. The animal's TMJ condylar cartilage surfaces in both sides were divided into 9 areas respectively according to locations, and the stress distribution on each area was analyzed quantitatively using the finite element method (FEM). The evaluation indexes included the von Mises stress, the maximum principal stress and the minimum principal stress.
Results: During unilateral MDO, the change of stress distribution on the condylar cartilage of the distraction side was much higher than that of the nondistraction side. On the distraction side, the anterior area of the condylar cartilage was the major pressive area; the transverse ridge area and the posterior area were the major tensile areas; anteroposterior view disclosed that the highest average von Mises stress was on the anterior area, followed by the transverse ridge area, and the lowest was on the posterior area; whereas viewed mesiolaterally, the average von Mises stress on the mesial 1/3 of the condyle was higher than that on the median and lateral 1/3.
Conclusions: The results of this study indicated that during unilateral MDO, the distraction force can lead to certain stress distribution on the condylar cartilage surface, which may bring about some structural changes of the TMJ.
Keywords: cartilage; Stress ;distraction osteogenesis