Date of Award
Spring 4-15-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Dentistry
First Advisor
Pradeep Bhagavatula
Second Advisor
Shengtong Han
Third Advisor
Stephanie Sidow
Abstract
Objective: To evaluate how the time interval between root canal obturation and the placement of a definitive restoration impacts the incidence of tooth failure, defined as non-surgical retreatment, apical surgery, or extraction. Methods: This 22-year-retrospective cohort study utilized electronic health records from the Marquette University School of Dentistry (MUSoD) axiUm database, analyzing 11,002 teeth treated between 2004 and 2026. Inclusion criteria required patients to be at least 18 years of age, categorized as established patients of record, with all non-surgical root canal treatments (NSRCT) meeting the 2020 AAE quality standards. The interval between obturation and restoration was categorized into seven cohorts: 0, 1–30, 31–60, 61–90, 91–120, 121–180, and >180 days. Procedures were further stratified by provider level: Pre-doctoral (Group S) and Resident (Group G). Survival was analyzed using Kaplan-Meier estimates and Cox proportional hazards regression. Results: Restoration timing was a highly significant predictor of tooth survival (p < 2e-16). For every 1-day increase in the time between RCT and final restoration, the risk of failure increases by 0.04% (HR: 1.0004). Teeth restored within the 31–60 day window demonstrated the highest survival rates at both 5 years (88.7%) and 10 years (86.0%). Patient age was a significant factor (p = 0.0343), with each year of age decreasing the hazard of failure by 0.45% (HR: 0.9955), while patient sex was not significant (p = 0.5501). A significant difference was observed between provider levels (p = 0.0333); Group S maintained a 16.45% lower risk of failure compared to Group G (HR: 0.8355). Conclusions: Timely placement of a definitive restoration is essential for long-term retention. To optimize prognosis, final restorations should ideally be placed within 60 days of root canal completion. While overall survival remains robust beyond 20 years with prompt intervention, significant delays, particularly beyond 180 days, substantially compromise long-term outcomes.