Introduction: The success of periodontal and endodontic treatments depends on the total recovery from both conditions regardless of their occurrence as independent or combined lesions. There is strong presumptive evidence that teeth with periodontal disease may cause pulpal inflammation and degeneration. Therefore, the goal of this study was to establish a correlation between periodontitis and pulp volume. Methods: Thirty-four dental images from 17 patients obtained by cone beam 'computed tomography were analyzed by medical software to create three-dimensional images. Paired t test analysis was used for statistical analysis. Results: The statistical analysis showed that periodontitis had a significant effect on the volume and surface areas of the dental pulp (P <.05). Conclusions: The findings of this study showed that periodontitis causes pulp volume to reduce by approximately 20%. The use of three-dimensional models provides better understanding of the dental anatomy before endodontic treatment and, consequently, improvement of treatment outcomes. Additional studies are needed to investigate the effect of periodontal disease on pulp volume and surface area.