Abstract: Objective To explore the effect of masticatory force on development of condylar cartilage and the BrdU labeling in growing rabbits.Methods Thirtytwo,10dayold New Zealand white rabbits were divided into two groups randomly.One group received the normal hard diet and the other group received a powder soft diet.Both groups were injected intraperitoneally with bromodeoxyuridine(BrdU) 50mg/kg for 2 consecutive weeks and then sacrificed at 2,4,6,8 weeks after the first BrdU injection.Presence of BrdU was detected using immunohistochemistry and morphological change was examined by HE staining.Results Compared with the softdiet group,the thickness of anterior part of condylar cartilage in the harddiet group increased significantly.There was no significant change in the thickness of intermediate part of condylar cartilage.The thickness of posterior part of condylar cartilage was thicker in the softdiet group.Immunohistochemical analysis revealed staining of BrdU localized in the all cartilage zones and subchondral bone.BrdUpositive cells were abundantly detected in the proliferative zone.The BrdU labeling rate of harddiet group in anterior intermediate and posterior part of condylar cartilage was higher than the softdiet group significantly in the 2nd week.The BrdU labeling rate of softdiet group in intermediate and posterior part of condylar cartilage was higher than the harddiet group significantly in the 6th week.In 8th week BrdUpositive cells couldn′t be detected in both groups.Conclusions The growing rabbits with low masticatory force have a slow proliferation initiation.It suggests that the proper masticatory force can promote the proliferation of cell in cartilage and the development of condylar is still affected by the internal factor such as gene.

Key words: condylar cartilage, mastication, bromodeoxyuridine labeling, proliferation, rabbit