With the use of amalgam for dental restorations on the decline due to concerns about the effects of mercury and esthetics, alternative materials such as glass ionomers and composite resin are increasingly be requested by patients. Although these new materials are esthetically pleasing, their longevity has not been studied extensively.
After systematically reviewing studies examining the longevity of routine dental restorations in permanent posterior teeth prior to 1999, only eight of those studies met predefined criteria for quality. Many of these reported median survival time; that is, the lifetime a particular restoration has a 50% chance of exceeding. Though there was considerable variation in the studies, with the median survival time of amalgam, for example, ranging from 5-8 years in one to study, to 23 years in another, overall, the studies showed that half of all restorations can be expected to last between 10 and 20 years.
A more recent study by a single dentist found that composite resin restorations, placed in adults, failed more quickly than amalgam restorations (median survival time 7.8 vs. 12.8 years). Increasing age of the patient, the lack of pulpal vitality in the tooth, failure to use base material and premolar vs. molar restorations were all contributing factors that increased the risk of restoration failure.
A relatively quick and simple study of restoration longevity uses a cross-section approach. In 1997, and again in 2000, Frorss and Widstrom conducted two such cross-sectional studies in Finland, were dentists selected at random completed surveys requesting information on restorations placed during a given period. Where the restoration replaced a previous restoration, information regarding the age of the failed restoration was also collected. The survey conducted in 1997 revealed that patients in the range of 20 to 39 years of age had amalgam restoration fail on average at 10.5 years, while glass ionomer and composite resin failed on average 4.5 years and 4.0 years respectively. In older patients (over 39), the median age of failed restorations was 13.5, 5.0 and 5.8 years respectively. The 2000 survey revealed the overall median age of failed restoration was up slightly, with the results being 15.5 years for amalgam, 7.4 years for glass ionomers and 7.0 years for composite resin.
For children under the age of 17, data was collected only in the earlier survey where the median age of failed restorations in permanent teeth proved to be quite low (3.5 years for glass ionomers and 2.2 years for composite resin; data for amalgam was too rare in this population to be analyzed). In was speculated by the authors that the much lower median age of failed restorations in children under 17 years of age compared to that of adults was the result of the difficulty in achieving ideal conditions for placed restorations in children.
Although the available evidence all points to composite resin and glass ionomer restorations failing earlier than amalgam,durability, esthetics and potential consequences for systemic health and the environment must all be considered when choosing a material for dental restorations.
Article fromThe Colgate Oral Care Report, Volume 15, Number 3, 2005.
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