Pulp Pathology as Indicated by Endodontic Treatment Following Extensive Coronal Restorations: Incidence and Timing in a 10-Year Swedish Register-Based Study

To assess the proportion of restored teeth that later underwent endodontic treatment and the timing of this outcome and to identify associated risk factors. Tooth extraction was analysed as a secondary outcome.

This register-based complete enumeration cohort study included all teeth, without prior root canal treatment, undergoing major direct and indirect restorations between 2014 and 2019 in a Swedish Public Dental Service setting. Teeth were followed through dental records for up to 10 years, with a study end date of 31 December 2024. The predefined study outcomes were initiation of endodontic treatment, used as an indirect indicator of pulp pathology, and tooth extraction. The statistical methods applied in the study's time-to-event analyses accounted for clustering of teeth within patients.

The study included 160 393 patients (mean age: 57.1 years, SD = 16.3), contributing 271 368 restored teeth. The majority of teeth were molars (53.5%), and most restorations were direct (85.3%). During follow-up, 15 352 teeth (5.7%) underwent endodontic treatment, with a mean time to treatment = 2.89 years (SD = 2.48); almost 30% of treatments occurred within 1 year of restoration. Competing risk regression analysis indicated that direct restorations, younger age, and posterior teeth have a higher hazard of endodontic treatment. In total, 17 830 (6.6%) teeth were extracted during follow-up. Overall, 25.9% of teeth that underwent endodontic treatment were extracted later during follow-up, and the extraction hazard for these teeth was 6.41 times that of teeth with no endodontic treatment event (hazard ratio 95% confidence interval 6.14-6.69, p-value < 0.001). Event-free teeth were followed for a median of 13.5 months (mean = 2.55 years), although indirectly restored teeth were lost to follow-up significantly earlier than directly restored teeth (p-value < 0.001).

Most restored teeth did not need endodontic treatment during follow-up; however, when required, treatment was initiated during the first year. Direct restorations were more frequent among younger patients and showed negative associations with time to endodontic treatment and time to extraction event.