The natural treatment history of teeth restored with large amalgam or crown restorations: Factors associated with subsequent treatment, the timing of subsequent treatment and the costs associated with treatment selection

Background. This project was designed to assist in proper evaluation of dental treatment options and determine the most appropriate treatment. The purpose of this project was to follow and compare the natural histories of posterior teeth that were treated with four or more surface amalgam fillings (LA) and posterior teeth treated with a large amalgam filling and a subsequent full-coverage crown (LAC). This project involved a series of studies comparing LA and LAC teeth while evaluating the likelihood of subsequent treatment, factors that are associated with subsequent treatment, timing of subsequent treatment, and costs associated with subsequent treatment. Methods. We used retrospective data from The University of Iowa, College of Dentistry data-base. Teeth that received a LA in 1987 and 1988 were targeted for evaluation and were followed for over 10 years. Targeted teeth that received a subsequent crown within a year of the LA were classified as LACs, remaining teeth were classified as LAs. To compare LA and LAC teeth subsequent treatment was used to construct Treatment Outcome Trees (TOT). To evaluate patient and tooth factors associated with outcome, multiple logistic regression models, Kaplan-Meier survival estimates, Log-Rank p-values, and Cox proportional hazard models were created. Lastly, to determine the effect of costs, a cost-effectiveness analysis was completed. Results. LAC teeth were found to receive less subsequent treatment as well as less catastrophic treatment. LA teeth had a faster rate of receiving subsequent (∼6X) and catastrophic treatment (∼2X). Restoration type, gender, grinding, and broken were associated with the need for subsequent treatment. Only restoration type and gender were associated with the need for catastrophic treatment. The timing of subsequent treatment was related to the interaction of restoration and arch type, and proximal contacts. The timing of catastrophic treatment was related to all these variables plus gender. The cost-effectiveness ratios are higher at both 5 and 10 years for LAC teeth compared to LA teeth. Additionally teeth in men and in the mandibular arch had higher cost-effectiveness ratios than their counterparts. Conclusion. The consideration of alternative treatments for a tooth requiring extensive restoration includes longevity, outcome, cost and patient factors.