REMODELING OF THE TEMPROMANDIBULAR JOINT FOLLOWING DIFFERENT RATES OF MANDIBULAR DISTRACTION OSTEOGENESIS (AN EXPERIMENTAL STUDY)

Introduction: patients with craniofacial deformities resulting from trauma, infection, tumors and congenital defects usually require skeletal expansion. Tradition treatment methods, involve autogenous bone grafting, which often results in problems including graft resorption, infection and donor site morbidity. Distraction osteogenesis has been adopted more and can help overcome these problems.
Aim of the work: the purpose of this study was to compare histologically the effect of bilateral distraction osteogenesis of the mandibular body at different rates on the integrity of the condylar cartilage in rabbits.
Material and Methods: This study was performed on 2 groups of twelve healthy rabbits (adult male) : (group 1 and group 2) each group (n=6 rabbits, and 12 joints). Two rabbits (4 joints) in each subgroup according to the post distraction period (1, 2, and 4 weeks). In group 1, the distraction was performed daily at rate of 1 mm for 5 days. In group 2, the distraction was performed twice daily at rate of 1.5 mm (3 mm per day) for 5 days.
Results: Animals in both groups (1 and 2) showed changes in condylar head, which seemed to be reversible according to the post distraction period. After the first week, condylar layers were decreased in thickness with irregular fibrous outline, bone trabeculae were decreased in number and invaded by large number of osteoclasts. After the second week, the condylar head showed evidence of regeneration of all layers including the disc. After the fourth week, the subchondral area started to be refilled with new bone with numerous osteoblast. Group 2 (3 mm per day) showed more bone and collagen formation.
Conclusion: this experimental study reported that distraction rates of 1 mm per day and 3 mm per day showed degenerative change in the TMJ condylar cartilage in the first post distraction week. At the second week, all the condyles showed adaptive and remodeling signs. Regeneration to the normal histological structure appeared in the fourth post distraction weeks, in group 2 (3 mm per day) more than in group 1 (1 mm per day).