Objective To study the histological change of microscrew-bone interface, detect the relative cytokine of gingival crevicular fluid, and explore the impossible mechanism of peri-implantitis. Methods Four male Beagles were collected. Randomly select one side of animals jaw as the experimental group to induce the peri-implantitis, and another side as the controll group. Four microscrews were implanted on each side. In the 1st, 2nd, 3rd, 4th weeks after implantation, collect peri-implant sulcular fluid（PISF） and detect tumor necrosis factor-α（TNF-α） levels before sacrificed, and the harvest tissue were observed in histological ways. Results According to the extension of time after implantation, the experimental group showed visible progress of interface destruction: 1st week after implantation showed large numbers inflammatory cells collected at the neck but did not undermine the cortical bone; 2nd week after implantation, cortical bone were observed angular absorption; Bone resorption continued to develop and at the 4th week, bone resorption were enlarged to the second thread of microscrew and the interface was filled with a large number of collagen fibers. Conclusion The destruction of interface began at the neck of microscrew, and the further development was along the interface in depth. Both microscrews with peri-implantitis and the healthy controls showed the presence of TNF -α. Inflammation accumulation might trigger the up-regulation of TNF-α level, and the onset of inflammation would enhance the up-trend.
