Abstract: Objective: To establish the experimental peri-implantitis mouse models,to investigate the expression of tumor necrosis factor-α (TNF-α) in the gingival tissue of the experimental peri-implantitis model mice, and to elucidate its pathogenic effect on peri-implantitis. Methods: Eighteen 4-week-old C57BL/6J male mice were divided into blank group,control group and model group(n=6); the right and upper first molars were removed, and the custom implants were immediately implanted. After 4 weeks of healing, the mice in model group were used to establish the peri-implantitis models with ligation method; the mice in blank group and control group didn't receive any treatment. The mice in blank group were killed on the 0th day of ligation (before the ligation treatment); the mice in control group were killed on the second week without ligation;the mice in model group were killed on the second week of ligation of the neck of the implant with 5-0 silk thread.The upper jaw bone and gingvival tissue samples of the mice in various groups were obtained,and the morphology of peri-implant gingival tissue were observed with surgical microscope. Micro-CT scanning was used to measure the bone height and bone density around the implants and RT-PCR method was performed to detect the expession level of TNF-α mRNA in the gingival tissue. Results: The morphological observation showed that the gingival tissue around the implants in model group appeared obvious redness, edema, softening and exudation, while there were no visible signs of inflammation in blank group and control group. Compared with control group, the proximal, distal, buccal and zygomatic bone heights and the alveolar bone dellsity around the implants of the mice in model group were significantly reduced (P<0.05), and the expression level of TNF-α mRNA in the gingival tissue of the mice in model group were significantly increased (P<0.05). Compared with blank group, the proximal, distal, buccal and zygomatic bone heights and the alveolar bone density around the implants of the mice in control group had no statistical differences (P> 0.05), and the expression level of TNF-α mRNA in the gingival tissue of the mice in control group had no statistical difference (P> 0.05). Conclusion: An experimental mouse model of peri-implantitis is successfully established with ligation-inducing method. TNF-α is highly expressed in the gingival tissue of the model mice, which may have a role in promoting the pathogenesis of peri-implantitis.

Key words: peri-implantitis, immediate dental implant loading, tumor necrosis factor-alpha, disease models, animal