Abstract: OBJECTIVE To explore effects of peri-implantitis on proliferation and differentiation of mandibular osteoblasts, so as to provide references for clinical tretment. METHODS Seven cases of patients with implant loosening and were pulled out were collected as observation group, and 7 cases of healthy pulled out third molars as control group. The jaw bone tissue of the two groups of patients were taken for isolation, culture and purification of osteoblasts. MMT was used to assay osteoblasts proliferation, RT-PCR was used to assay osteoblasts Ⅰ collagen (Col Ⅰ) mRNA level, and Western blot was used to detect Col I protein level of osteoblasts. RESULTS The OD value of osteoblasts of observation group was lower than that of control group at the 7th day (P<0.05), the OD value of osteoblasts of observation group was lower than that of control group at the 3rd day, but the difference was not significant. The expression of Col Ⅰ protein of osteoblasts of observation group was significantly lower than that of control group (P<0.05 ). CONCLUSION Peri-implantitis can inhibit the proliferation and differentiation of the mandibular osteoblasts.