291: Tumor necrosis factor-α aggravates orthodontically root resorption

Objective Tumor necrosis factor (TNF)-α is known as inflammatory cytokine of potent osteoclast activate factor. TNF-α together with interleukin (IL)-1 promotes differentiation of osteoclast from osteoclast precursor and engages in inflammatory bone resorption. Root resorption is one of a complication associated with orthodontic tooth movement, and that is derived from excessive activation of odontoclast. However, the relationship with tooth root resorption has not been revealed. In this study, therefore, the relationship between TNF-α and tooth root resorption was examined. Materials and methods: Twenty patients who had been receiving orthodontic treatment (fifteen-control subjects and five-severe root resorption subjects) participated in this study. Gingival crevicular fluid (GCF) was collected from the patients. To determine the TNF-α level, the eluted GCF was used for Western blot analysis.25 g of orthodontic force was applied to the upper first molars in mouse in vivo. HE staining and immunohistochemical staining with TNF-α was performed. Human periodontal ligament cells (hPDL cells) were subjected to compressive forces (CF) for up to 48 h in vitro. Real time PCR and enzyme-linked immunosorbent assay (ELISA) were performed to evaluate the production of TNF-α.In addition, we investigated that the effect of TNF-α on osteoclast through TRAP staining and pit formation assay. Results: The TNF-α and RANKL levels were significantly higher concentration in the severe root resorption group than in the control group by Western blot analysis.In immunohistochemical staining, TNF-α positive cells were significantly increased in the root resorption area at 7 days. In vitro study, the mRNA expression of TNF-αwas found to increase by CF. Moreover, the number of TRAP positive cells significantly increased in the TNF-α with RANKL group. Furthermore, the area of resorption pits increased marginally in the same group. Conclusions: TNF-α may induce by CF promote odontoclastogenesis and aggravate root resorption.