Purpose: There are a variety of surgical methods to treat deformed jaws. However, mandibular protrusion and asymmetrical cases are dominant in Japan. No matter which surgical method isused, postoperative changes in temporomandibular joints (TMJs) are the most undesirable complications. Altered stress on the condyle and the surrounding tissue frequently cause morphological change of the TMJ. The purpose of the present study was to assess morphologic change of the craniomandibular joint (CMJ) in rabbit, especially simultaneous mandibular body rotation, following unilateral mandibular body shortening osteotomy.
Materials and Methods: Adult male Japanese white rabbits (3kg, 12 to 16 weeks old) were used in this study. Experimental mandibular osteotomy was achieved in the right unilateral CMJ under general anesthesia. The surgery included vertical mandibular body osteotomy 5 mm in width after masseter muscle abrasion. Then the anterior and posterior osseous segments were fixed with wire at the two previously made holes. This postoperative condition was setback 5 mm for reduction of mandibular protrusion. Postoperative assessments were performed at 2, 4, 8, 12 and 24 weeks. The size of the mandible, glenoid fossa, and articular eminence were measured with a caliper.
Results: The condylar mediolateral width in the right operative side was significantly smaller than that of the left non-operated control side after 8 postoperative weeks (p<0.05). However, the mediolateral width of eminence on the right showed no difference from that on the left. The morphological changes of condylar heads and dental arch were evaluated by an internal angle at the intersection of mesiodistal line and anteroposterior line. There were significant differences in these angles between the right and the left condylar heads after 4 postoperative weeks (p<0.05)
Conclusion: The present experimental study disclosed morphological changes in CMJ caused by right unilateral mandibular osteotomy. Condylar remodelling was observed with the changed load on the CMJ after osteotomy. Postoperative morphological changes suggested that the performance of biological adaptation was achieved in rabbit CMJ.