Abstract:

Objective　To investigate the effect of bilateral mandibular distraction osteogenesis in the condyles.Methods　16 adult hybrid dogs were randomly divided into normal control group and experiment group. Experimental dogs underwent bilateral mandibular osteodistraction at a rate of 1 mm/day. 4 dogs were killed respectively in distraction period, 2 and 8 weeks after com- pletion of 10 days distraction. The bilateral condyles specimens were harvested and examined with histological and immunohisto- chemical methods.Results　Comparedwith normal control group, various degrees of irregularities and erosionwere found in fibro- cartilage of condyle in experiment group, including damage in fibrous layer, hyperplasia layer and proliferative layer and osteogenic activity in cartilage layer. Asignificant increase ofTGF-β1 expressionwas also found in experiment groups. TGF-β1 positive stain- ing was noted in hypertrophic cell, matrix and chondroblast, osteoblast and matrix in osteogenic activity areas. These changeswere the most obvious in 2 weeks after completion of distraction.Conclusion　Gradual bilateral mandibular distraction at a rate of 1 mm/day brought degenerative changes of condyle, but the changes are reversible.

Key words: distraction, temporomandibular joint, transforming growth factor-β1