Hydroxyapatite (HA) has high biocompatibility. Because, it is non-absorbable and remains in the bone, its influence on the surrounding tissue must be considered. We placed dental implants in the lower right first premolar region and then packed HA around the fixtures and investigated the stress on the surrounding bone during load application using the three-dimensional finite element method. Three-dimensional image data of the edentulous mandible and implant were imported into analysis software. A three-wall bone defect model was fabricated where HA was filled on the distal of the implant, and the stress on the mesial surface adjacent to the implant body where the load was applied was measured using nonlinear analysis with a friction coefficient of 0.33, and using linear analysis. In the HA filling group, equivalent stress, compressive stress, and tensile stress increased with nonlinear analysis compared with linear analysis. There was no difference in stress in the models without bone defects. Compressive stress was greater than tensile stress in all models. When HA is used as bone filling material during dental implant placement, osseointegration is the key to success. (J Osaka Dent Univ 2020; 54: 127-134)