Death and proliferation of chondrocytes in the degraded mandibular condylar cartilage of rats induced by experimentally created disordered occlusion

To investigate the effect of experimentally created disordered occlusion (ECDO) on cell death and proliferation in rat mandibular condylar cartilage. Sprague-Dawley rats were randomly assigned to experimental and control groups. In the experimental groups, ECDO was created by the dental orthodontic method. By means of histological evaluation, immunohistochemistry and TUNEL staining, we studied the histomorphological changes, the death and proliferation of chondrocytes. Time- and sex-related progressive histologic degradation was observed in the condylar cartilage of ECDO rats, accompanied with diminished chondrocyte proliferation in the female 12-week ECDO subgroup (P < 0.05). An increase in the number of apoptotic chondrocytes was seen in both the female 8- and 12-week ECDO subgroups and in the male ECDO 12-week subgroup (all P < 0.05), but not in the male ECDO 8-week subgroup (P > 0.05). ECDO induces degradation in the rat condylar cartilage accompanied by an increase in chondrocyte death.