Survival Analysis Of Crown Margin Repair, A Retrospective Study

Objectives: Repairing restorations, including crowns, is a more minimally-invasive and cost-effective treatment option than replacement. The objective of this study was to determine the survival of crown margin repairs and the factors that were associated with the survival.
Methods: For this retrospective survival analysis, electronic health records of patients since January 2008 were reviewed for 1012 crown margin repairs completed at The University of Iowa College of Dentistry. Patients of ages 25 and above were included in the study. Each subject had a crown margin repair done at the start of the study and restorations were followed until end of the study in August 2019 or until they failed. Failure was defined as having an additional repair, crown replacement, or extraction. In this survival analysis, Cox Proportional Hazards Model was used to study the relationship between time until failure (in days) and the variables; patient’s age, caries risk assessment, tooth type and jaw, number of surfaces repaired, type of repair material, crown type, root canal treatment, provider type.
Results: About 36.3% of the restorations failed during the follow-up, with the median survival time being 1875 days (5.1 years). In the final model, only repair material remained as significant covariate. Hazard ratios for glass ionomer (GI), resin-based dental materials (RBC - dental composite, flowable dental composite or sealant) and resin modified glass ionomer (RMGI) when compared to amalgam were 2.0, 1.5 and 1.0 respectively. Of these, the values for GI and RBC were statistically significant.
Conclusions: The type of restorative material was the only significant factor associated with survival of the crown margin repairs.