Survival analysis of teeth following clinical crown lengthening and crown insertion procedures up to 14 years: A retrospective cohort study.

Background: The purpose of this study was to conduct survival analysis of teeth following clinical crown lengthening procedures (CLPs) and crown insertions via a retrospective cohort study.

Methods: Patient- and tooth-related data were collected from 268 participants who received CLPs from 2009 to 2015. The Kaplan-Meier curve and the log-rank tests were used to estimate the probability of survival and compare the survival probabilities among different variables. A Cox multivariate proportional hazard regression model was used to investigate the collective effects of root canal treatment (RCT) and the types of opposing dentition.

Results: The rate of tooth loss was 21.6% during the observation period from 1 to 14 years, with 58 teeth extracted. The most attributable reason for tooth extraction was coronal tooth fracture, followed by endodontic failure such as root fracture. The survival probability was 0.87 at 5 years and 0.7 at 10 years. No significant differences in the survival probabilities were found among different providers and locations, the presence of a post, and the types of crowns. The hazard ratio for tooth loss was 6.3, 95% confidence interval (CI) [2.6 to 20.9] in the teeth with RCT (p < 0.001) and 2.4, 95% CI [1.1 to 4.8] in the teeth occluding implant-retained prostheses (p = 0.016).

Conclusions: Tooth loss following CLPs and crown insertions appeared least among the teeth without RCT when occluding natural teeth, while tooth loss was most among the teeth with RCT when occluding implants.