Abstract

Background: Investigating the pattern of extension in the periapical (PA) inflammatory lesions is important in the treatment plan and prognosis of treatment. Introduction: This study evaluated the topography of PA inflammatory lesions in the first molars using cone-beam computed tomography (CBCT). Methods: In this descriptive study, 197 CBCT images about patients in the age group of 14–77 years were analyzed. The maximum extension of the PA lesion in the three orthogonal planes related to the regions of maxillary and mandibular first molars was measured and reported in millimeters. Measurements were compared based on age, gender, dental arch, and root type. Statistical analysis was performed using percentages, repeated measure ANOVA, paired t-tests, and Pearson correlation coefficient. The significant level was set at 0.05. Results: The highest total mean lesion extensions were in the vertical plane followed by the buccolingual and mesiodistal plane. There was a statistically significant difference between the extension of the PA lesion in the vertical and mesiodistal (p < 0.001), vertical and buccolingual (p = 0.001), as well as the mesiodistal and buccolingual planes (p = 0.027). In the maxilla and mandible, the highest mean lesion extension was in the vertical, buccolingual, and mesiodistal plane, respectively. According to the root type, there was only a statistically significant difference in lesion extension in the buccolingual plane and between the mesial and distobuccal roots (p = 0.030). Conclusion: Given the limitations of the present study, regarding the extension of the PA lesion in the first molar region, the bone structure of the maxilla and mandible follows a precise and delicate pattern. In this regard, future studies in different communities and races should be designed to address this issue in different communities. In addition, CBCT is a reliable imaging method to evaluate the extension of the PA lesion both morphologically and morphometrically. Copyright © 2025 Maryam Kazemipoor et al. International Journal of Dentistry published by John Wiley & Sons Ltd.