Bone Abstracts

Purpose: The purpose of this study was to investigate the bony change of mandibular condyle when the originally less-loaded or unloaded surface was subjected to functional loading by the newly designed animal experiment, and to evaluate whether this experiment is adequate for the animal model of condylar resorption due to mechanical loading.

Methods: Twelve adult male New Zealand white rabbits were used. Unilateral oblique vertical body osteotomy (UOVBO) was performed on the right side of the mandible. The proximal segment was rotated counterclockwise by 1 mm (group I, n=6) or 3 mm (group II, n=6). The rabbits were sacrificed four weeks postoperatively, and osseous changes of condyles were analyzed using micro-computed tomography and histological evaluation. The comparison was performed between condyles on the right and left (control) sides. Since the left condyle might be affected by the operation on the right side, the results were also compared with the healthy control (n=2, no operation).

Results: The CCWR of the proximal segment after UOVBO led to osteoporotic change of condyle including significantly reduced bone volume, decreased bone mineral density, thin trabecular thickness, small trabecular number and wide trabecular separation (P<0.05 for all parameters), with thinning of condylar cartilage and reduced density of cartilaginous cells compared with the left condyle. However, those changes were not affected by the amount of CCWR of the proximal segment. There was no significant difference between the left condyle and healthy control.

Conclusion: The osteoporotic change of condyle occurred with the CCWR of the proximal segment. We suggest that 1 mm-CCWR of the proximal segment is an adequate animal model to observe bone and cartilage alterations after directional change of functional loading, not an animal model for condylar resorption due to mechanical loading.