Twenty implants of 3.75mm in diameter(Neoplant, Neobiotech, Korea) were used to evaluate the correlation between the resonance frequency analysis (RFA) and the radiographic method for periimplant bone change under in vitro conditions. To simulate peri-implant bone change, 2mm-deep 45° range horizontal defect and 2mm-deep 90° range horizontal defect area were serially prepared perpendicular to the X-ray beam after conventional implant insertion. ISQ values and gray values inside threads were measured before and after peri-implant bone defect preparation. ISQ value of resonance frequency analysis was changed according to peri-implant bone change and gray value of radiographic method was changed according to peri-implant bone change. In horizontal defect condition, relatively positive correlation were between ISQ and gray values(r=0.663).