Introduction In a clinical situation, an apically resected tooth is often accompanied by a varying degree of periodontal bone loss. The purpose of this study was to assess the influence of apical root resection combined with periodontal bone loss on the biomechanical response of a single-rooted tooth. Methods A basic intact model and a basic apically resected model of the upper central incisor were selected for the numerical analysis. From each basic model, 6 models were developed assuming different amounts of periodontal bone loss (0, 0.5, 1, 1.5, 2, and 3 mm). Maximum von Mises stress (σ max), maximum tooth displacement (ΔR max), and effective crown-to-root ratio (α) were calculated for each condition. Results There were only marginal differences (a 2.1% difference in σ max and a 16.9% difference in ΔR max) between the biomechanical responses of the intact model and the apically resected model when the tooth was supported by a normal periodontium. However, when destruction of the periodontium was assumed, the intact model and the apically resected model responded differently. The difference increased as the periodontal bone loss progressed, resulting in a 68.7% difference in σ max and a 56.3% difference in ΔR max when the periodontal bone loss increased to 3 mm (α = 0.48). Conclusions Although the biomechanical response of an apically resected tooth was relatively stable when the tooth was supported by a normal periodontium, the apically resected tooth showed a more deteriorated response compared with the intact tooth as the periodontal bone loss progressed.
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