Abstract: PURPOSE: To investigate the gross manifestation and tissue destruction at different inflammatory periods of ligature-induced peri-implantitis in mice model, and to evaluate the changes of interleukins level in the gingival crevicular fluid of implants at different stages. METHODS: Forty 4-week-old male C57BL/6N mice (18-22 g) were used and the maxillary right first molars were extracted, custom-made pure titanium machined screw type implants (1 mm×1.5 mm) were placed immediately, one implant per animal. Four weeks later, the mice were randomly divided into experimental and control group. 5-0 cotton ligatures were applied around implant necks in the experimental group to induce peri-implantitis. Alveolar bone loss and clinical index records of the soft and hard tissue were assessed every 5 days following ligature.According to the measured data, the stages of peri-implantitis were ascertained. The gingival crevicular fluid of implants in the early, middle and late stages in the experimental group was extracted and the expression of IL-1α, IL-1β, IL-6 and IL-17A was detected. SPSS 22.0 software package was used to analyze the data. RESULTS: Alveolar bone absorption of all the mice in the experimental group reached 25% 10 days after ligature. This time point was early stage of peri-implantitis. On day 20, the alveolar bone loss around implant in 95% of mice in the experimental group reached 25%-50%, which was identified as middle stage. The alveolar bone loss of all mice in the experimental group was over 50% 30 days following ligature, which was confirmed as late stage. Compared with the early stage, the expression of IL-1α and IL-6 decreased significantly in the middle stage; while the expression levels of IL-1α, IL-6 and IL-17A decreased significantly in the late stage. CONCLUSIONS: Mice models with peri-implantitis of various stages were successfully established by ligature and the expression of IL-1α, IL-1β, IL-6 and IL-17A in different stages of disease was detected, which provided a basis for further research the relationship between interleukin content and peri-implantitis development.

Key words: Ligature induced, Peri-implantitis, Staged model, Interleukin