OBJECTIVETo investigate the effect of bilateral mandibular distraction osteogenesis in the condyles.

METHODS16 adult hybrid dogs were randomly divided into normal control group and experiment group. Experimental dogs underwent bilateral mandibular osteodistraction at a rate of 1 min/day. 4 dogs were killed respectively in distraction period, 2 and 8 weeks after completion of 10 days distraction. The bilateral condyles specimens were harvested and examined with histological and immunohistochemical methods.

RESULTSCompared with normal control group, various degrees of irregularities and erosion were found in fibrocartilage of condyle in experiment group, including damage in fibrous layer, hyperplasia layer and proliferative layer and osteogenic activity in cartilage layer. A significant increase of TGF-beta1 expression was also found in experiment groups. TGF-beta1 positive staining was noted in hypertrophic cell, matrix and chondroblast, osteoblast and matrix in osteogenic activity areas. These changes were the most obvious in 2 weeks after completion of distraction.

CONCLUSIONGradual bilateral mandibular distraction at a rate of 1 mm/day brought degenerative changes of condyle, but the changes are reversible.