Purpose: Root fracture is a common and serious cause of abutment tooth loss. No studies to date have comprehensively assessed the individual contributions of the factors that increase stress on abutment teeth. The purpose of this study was to analyze the stress distribution in abutment teeth based on a three-dimensional finite element model and to analyze the factors that affect stress distribution. Materials and Methods: Models were generated from the computed tomography data of a single patient, consisting of a mandibular second premolar abutment tooth, bone, residual mucous membrane, and a partial removable dental prosthesis (PRDP). Four models were prepared using different types of endodontic posts and cores. Akers clasps were used for the simulated PRDPs, and a vertical load was applied to the occlusal surface of the PRDPs. Debonding between the post and root was simulated. The Young modulus of the residual ridge was reduced to simulate a poor fit between the denture base and the residual ridge. Stress distribution in the abutment tooth root was observed, and the maximum principal stress was evaluated. Results: The nonmetal post model and the mesial rest model reduced stress concentration in the root. The stress increased in models simulating debonding and poor fit. The results of the multiple linear regression analysis confirmed that debonding and poor fit were significantly associated with root stress. Conclusion: Within the limitations of this study, it is suggested that the bonding integrity of posts and adequate fit of the denture base are important factors affecting the longevity of abutment teeth for PRDPs.