Amalgam versus Composite Resin Restorations: Comparative Survival Rates over Time

To estimate and compare the survival rate of amalgam and composite resin restorations in a high-risk population with universal public coverage for dental care and to analyse the change in survival rates over a 10-year period of restoration placements.

Method:

Health Canada provided aggregate censored data on treatments billed by dentists under its Non-Insured Health Benefits (NIHB) Program for the period  April 1, 1999 to March 31, 2010. This programme covers the cost of dental care for Canada’s registered First Nations and recognized Inuit populations. The data contained 791,723 amalgam restorations and 1,870,123 resin composite restorations. No patients or providers could be identified from the data. We examined hazard functions of amalgam vs. resin composite restorations by year of restoration placement using Accelerated Failure Time (AFT) modeling with the lognormal distribution for the survival time.

Result:

There was a significant reduction in the annual number and proportion of amalgam restorations and significant increase in the annual number and proportion of resin composite restorations in every year of the study. Survival rates were not significantly different between restoration materials (1.14% higher for composite resin restorations, 95% CI -0.4% to 2.0%, p = 0.14).  The rate of restoration failure increased steadily and consistently over time.  For instance, the two-year failure rate for restorations placed in 2009 was 33% higher than the two-year failure rate for those placed in 1999.

Conclusion: Failure rates of resin composite restorations were not significantly different from failure rates for amalgam restorations, but they cost considerably more.  However, failure rates increased over time for both materials which may reflect changes in provider behavior.  The increased cost of resin composite restorations versus amalgam restorations means the cost to Health Canada will increase over time if the trend towards greater use of composite resin restorations continues