Beyond Root Canal Success: Impact of Periodontal Health and Crown Rehabilitation on the Prognosis of Endodontically Treated Teeth: A Prospective Cohort Study

Background: Periodontal support and definitive crown rehabilitation may influence outcomes following root canal treatment (RCT).Composite clinical-radiographic success, complete periapical healing, and tooth survival are distinct endpoints.Objective: To compare 12-month composite clinical-radiographic success across four combinations of baseline periodontal status and subsequently assessed crown quality following primary RCT of posterior teeth, and to explore additional endodontic and restorative associations.Methodology: This prospective observational cohort comprised 240 adults, each undergoing primary nonsurgical RCT of one posterior tooth with planned crown rehabilitation.Of these, 204 completed the 12month follow-up.Periodontal indices were evaluated at baseline and at three, six, and 12 months.Longitudinal changes were assessed using repeated-measures analysis of variance (ANOVA) with the Greenhouse-Geisser correction; exploratory associations with treatment failure were examined using Firth penalized logistic regression.Results: Among 204 participants with 12-month outcomes, 168 (82.4%) met the composite success definition and 36 (17.6%) experienced failure.Complete radiographic healing occurred in 111 (54.4%), with ongoing healing in 47 (23.0%).Composite success ranged from 86/91 (94.5%) in the favorableperiodontal/adequate-crown group to 20/35 (57.1%) when both were compromised (χ² = 25.89,df = 3; P < 0.001).The adjusted odds of failure were higher with compromised baseline periodontal status (odds ratio (OR) = 5.43, 95% confidence interval (CI) = 2.27-12.98)and compromised crown quality (OR = 3.39, 95% CI = 1.45-7.92).All five periodontal parameters showed significant time effects (Greenhouse-Geisser-corrected P < 0.001).Conclusions: Baseline periodontal status and subsequently assessed crown quality were associated with 12month composite outcomes after RCT.Given the observational design, sparse failures and short follow-up, these findings should not be interpreted as causal effects or evidence of long-term tooth survival.