Effects of unilateral mandibular distraction osteogenesis on temporomandibular joint

To study the effects of unilateral mandibular distraction osteogenesis(MDO) on the temporomandibular joint(TMJ).Ten rhesus monkeys were used to perform right MDO. After 5 days, latency period, the distractor was initiated at the rate of 0.5 mmx2/day, totally 15 days. When MDO completed, and 2,4,6,and 12 weeks after MDO, X-ray films of bilateral TMJ were taken and one group of animals was sacrificed. Bilateral TMJ were obtained and paraffin slices were made HE and immunohistochemistry stains of TGF-beta1 were done on the slices.After MDO, the monkeys' mandible midline obviously deflected to the left side. The front teeth had open bite and reverse bite. The right molars were severely open bite and the left molars were reverse bite. From the X-ray film, we can see that the right condylar process moved backward and upward in the acetabulum, while the left condylar process moved forward and downward. On the slices, both sides of the TMJ showed different degrees of degeneration and proliferation, but the changes on the right side were more severe and obvious than the left side, and had involved all the cartilage's layers and the bone tissues under the cartilage. In some animals, there even appeared cartilage erosion and light histological changes of acetabulum. During the consolidation period, the open bite gradually closed, and the condylar process gradually moved to normal position. Twelve weeks after MDO, the open bite at the right side disappeared, but the front teeth open bite and reverse bite still existed. The right condylar process still lay a little backward and had some degree of degeneration. The left TMJ had the normal position and histology except for cartilage hypertrophy layer thickness. At different times during consolidation period, the positive stains of TGF-beta1 in condylar process on both sides were all more obvious than that of the control group.MDO can cause TMJ position change and light histological degeneration, but these changes can gradually rehabilitate in the future. TGF-beta1 may play a role in the reconstructive process of TMJ degeneration.PubMed06649-533