Mesial–Distal Patterns of Alveolar Bone Loss in Periodontitis and Peri-Implantitis: A Comparative Radiographic Study

Background/Objectives: Periodontitis and peri-implantitis are inflammatory conditions associated with progressive loss of supporting bone, but they differ in tissue architecture, biological response, and disease progression. Conventional radiographic assessment often reports bone loss as a global value, which may overlook site-specific mesial–distal differences. This study aimed to compare mesial and distal radiographic bone loss around natural teeth affected by periodontitis and dental implants affected by peri-implantitis, with a focus on quadrant 1. Methods: This retrospective comparative CBCT-based radiographic study analyzed 128 within-patient paired tooth/implant observations in quadrant 1. Mesial and distal bone loss values were recorded separately for natural teeth and corresponding implant sites. Each pair included one natural-tooth site and one implant site from the same patient, matched by comparable anatomical position and surface. Paired-samples t-tests were used, and mean differences were calculated as implants minus natural teeth. Given the multiple site-specific comparisons, p-values were interpreted as unadjusted exploratory findings. Results: Statistically significant differences were observed only on the mesial surface of anterior implants. Mesial bone loss was significantly greater around implants than natural teeth for central incisors (8.30 ± 3.31 mm vs. 4.90 ± 1.78 mm; mean difference = 3.39 mm; p = 0.004), lateral incisors (8.12 ± 3.57 mm vs. 4.94 ± 2.82 mm; mean difference = 3.18 mm; p = 0.028), and canines (5.99 ± 3.12 mm vs. 4.42 ± 1.26 mm; mean difference = 1.57 mm; p = 0.018). No statistically significant differences were observed for distal surfaces or posterior tooth/implant positions. Conclusions: Within the limitations of this quadrant-specific retrospective radiographic analysis, peri-implant bone loss showed a surface- and position-dependent distribution, with greater mesial bone loss around anterior implants. Separate mesial and distal assessment may provide additional value for periodontal and peri-implant monitoring.