Association between Apical Periodontitis and the Severity of Marginal Periodontitis in Root Canal-treated Teeth: A Retrospective Cohort Study.

Introduction: To evaluate whether the severity of marginal periodontitis is correlated with the development of apical periodontitis (AP) in root canal-treated teeth. The secondary aim was to investigate the variables associated with the development of AP in patients with different levels of bone loss.

Methods: This longitudinal, observational, retrospective cohort study entailed radiographic evaluation of root-canal-filled teeth in patients with and without periodontal involvement after a minimum period of 2 years. Independent, calibrated specialists evaluated the baseline periapical radiographs for the presence or absence of AP and periodontal bone loss (PBL). PBL was categorized as normal, mild, moderate, and severe. Logistic regression analysis was conducted to examine differences between groups and potential relationships among variables.

Results: A total of 1365 patients (2235 root canal-treated teeth) were initially screened, including 663 patients in the control group and 702 with periodontal involvement. 1011 root canal-filled teeth were included for analysis (normal PBL: 401 teeth; mild PBL: 304 teeth; moderate PBL: 228 teeth; and severe PBL: 78 teeth). 10.1% of teeth developed AP: 4.2% with normal PBL, 1.6% with mild PBL, 19.73% with moderate PBL, and 44.9% with severe PBL. Multivariable regression analysis showed no significant difference between teeth with normal and mild PBL (P > .05). Moderate PBL was associated with an 8.4-fold increase in the odds of developing AP (odds ratio [OR]: 8.38; 95% confidence interval [CI]: 3.06-22.98), whereas severe PBL was linked to a 41.3-fold increase (OR: 41.26; 95% CI: 8.15-208.95), both compared to normal PBL (P < .05). Furthermore, patients who smoke also showed a higher odd of developing AP (OR: 2.22; 95% CI: 1.11-4.46) (P < .05).

Conclusions: A clear association was found between the severity of marginal periodontitis and the development of AP in root canal-treated teeth. Additionally, smoking habit showed a significant association with the development of AP acting as a confounding factor.