Longevity of dental amalgam in comparison to composite materials

Caries is one of the most prevalent diseases worldwide. For (direct) restaurations of carious lesions, tooth-coloured composite materials are increasingly used. The compulsory health insurance pays for composite fillings in front teeth; in posterior teeth, patients have to bear the extra cost.

Amalgam is an alloy of mercury and other metals and has been used in dentistry for more than one hundred and fifty years. Composites consist of a resin matrix and chemically bonded fillers. They have been used for about fifty years in front teeth. Amalgam has a long longevity; the further development of composites has also shown improvements regarding their longevity.

This HTA-report aims to evaluate the longevity (failure rate, median survival time (MST), median age) of direct amalgam fillings in comparison to direct composite fillings in permanent teeth from a medical and economical perspective and discusses the ethical, legal and social aspects of using these filling materials.

The systematic literature search yielded a total of 1,149 abstracts. After a two-step selection process based on defined criteria 25 publications remained to be assessed.

The medical studies report a longer longevity for amalgam fillings than for composite fillings. However, the results of these studies show a large heterogeneity. No publication on the costs or the cost-effectiveness of amalgam and composite fillings exists for Germany. The economic analyses (NL, SWE, GB) report higher costs for composite fillings when longevity is assumed equal (for an observation period of five years) or longer for amalgam compared to composite fillings. These higher costs are due to the higher complexity of placing composite fillings.

Due to different study designs and insufficient documentation of study details, a comparison of different studies on longevity of direct amalgam and composite fillings in posterior teeth is difficult. Apart from the difficulties in conducting a randomized, controlled long-term study comparing the longevity of direct fillings, the fact that composites and adhesives used in a study have often already been replaced by the next generation of the product at the time of study publication presents an additional problem. Not only the filling material, but also patient parameters and local, intraoral factors (e. g. localisation of the filling) as well as the treating dentist have an impact on the longevity of dental fillings. In evaluating economic studies, one has to refer to the heterogeneity of data on longevity in the medical evaluation. The only effect parameter used in the studies is longevity, other aspects (e. g. long-term functionality) are only referred to in discussions. Extensive counselling of patients regarding the selection of the appropriate filling material is important.

Amalgam fillings show a longer longevity than composite fillings. Two out of six systematic reviews conclude that the expected survival time of composite fillings can be comparable to amalgam fillings. However, these conclusions are based on the results of short-term studies which usually overestimate the longevity of filling materials. From an economic standpoint, amalgam is the more economic filling material compared to direct composite fillings in posterior teeth when considering longevity as the only result parameter. Other aspects than longevity need to be considered in individually choosing the appropriate dental filling material. For future studies aiming to compare the longevity of amalgam and composite fillings, a sufficient sample size and study period, preferably in the setting of a private dental practice, should be aimed for. An evaluation of the cost-effectiveness of amalgam and composite fillings should take the functionality of teeth over a longer time period into account, as well as patients' preferences. The rapid development of composite materials and adhesives make short term revisions of these conclusions necessary.