Long-term survival of primary root canal treatment in teeth restored with indirect cuspal coverage restorations: a 10-year retrospective study

INTRODUCTION: This study aimed to evaluate the long-term survival of primary root canal treatment in posterior teeth restored with indirect cuspal coverage restorations. METHODS: Dental records of patients were retrospectively screened for primary root canal treatments between 1998 and 2019, followed by the placement of an indirect cuspal coverage restoration. Individual-, tooth-, and treatment-related variables were recorded. Surgical retreatment, apicoectomy and extraction were defined as failures. Survival rates of the primary root canal treatment were assessed by Kaplan-Meier statistics, and the mean annual failure rate (mAFR) after 10 years was calculated. The effect of the assessed variables on survival was determined by Log-rank tests and both univariable and multivariable Cox regression analyses (p<0.05). RESULTS: Overall, 607 teeth were included. The 10-year survival of primary root canal treatment was 89.1% (95%-CI: 85.3-93.1, 10-year mAFR: 1.14%).Three variables were significantly associated with survival in the multivariable model (p<0.05): type of indirect restoration (partial crown: HR (95%-CI) = 2.36 (1.11-5.00) [reference: full-coverage crown]), post placement (yes: HR (95%-CI) = 2.77 (1.04-7.40) [reference: no]), and time interval between obturation and restoration placement (>1 year: HR (95%-CI) = 2.03 (1.05-3.92) [reference: ≤1 year]). CONCLUSIONS: Primary root canal treatment in teeth restored with cuspal coverage restorations demonstrated a high long-term survival rate. Post placement was associated with reduced survival, whereas improved outcomes were observed in teeth restored with full-coverage crowns and in those receiving indirect restoration within the first year after root canal obturation.