The changing environment in which dentistry is being practiced will continue to have a dramatic impact on how dental amalgam is used and how its benefits are assessed. Declining dental caries rates in children and young adults indicate a need to reassess assumptions about the optimal approach to managing dental caries in the population. Historically, high rates of dental caries have led to a common view that caries attack was unavoidable and that, once a lesion was initiated, it would continue to increase in size if left untreated. The best long-term treatment was believed to be complete excision of carious tooth structure and adjacent sound tooth structure that might become carious in the future. The perception that there are "self-cleansing" areas of the teeth that do not predispose to carious attack was the rationale for extending cavity preparations beyond the extent of the carious lesion. This rationale was intuitive, however, and has proven to not be justified scientifically.
Effective preventive methods and the emergence of improved restorative materials permit a more conservative restorative approach and, generally, a wider spectrum of appropriate clinical choices than in the past. Although there is no single, ideal dental restorative material, certain materials offer advantages when used in specific clinical situations. For example, when minimal carious lesions occur in nonstress-bearing areas of posterior teeth, composite resins may be used as an alternative to dental amalgam, and they provide the advantage of preserving the maximum amount of sound tooth structure.
It is apparent that dentists will be treating patients with markedly varying oral health needs in the coming years. Some patients will present with rather low levels of dental caries that are not extensive in size. These patients will benefit from concerted prevention efforts and the use of smaller, nontraditional cavity preparations in posterior teeth, quite often employing newer dental restorative materials such as composite and glass ionomer cements.
Other patients will demonstrate higher levels and more extensive types of dental caries and/or many dental restorations that require replacement. Patients with extensive caries or in need of replacement restorations still will require aggressive preventive interventions but, generally, they will not be able to be managed as conservatively as patients with few, nonextensive caries. Restorations requiring replacement largely reflect the more destructive era of dental caries and the more extensive restorative approaches of the past. Once a large restoration has been placed, it cannot be replaced with a smaller one.
The qualitative value of a sound tooth versus a minimally restored tooth, a minimally restored tooth versus a moderately restored tooth, or a moderately restored tooth versus a totally rehabilitated tooth should not be overlooked. When dental caries are found in early stages or simply suspected, "wait and watch" is a rational alternative to definitive restoration, especially if patients can adopt more healthful practices and dentists can offer preventive interventions that may arrest early lesions.
The shift away from amalgam as the material of choice in many clinical situations has begun already and can be justified scientifically based on declining caries rates and the emergence of new and improved materials and methods. There continue to be, however, substantial oral health benefits that accrue to individuals and the population from the use of dental amalgam.
Based on a review of scientific evidence presented in this report, several broad recommendations can be made about the prevention and management of dental caries in the contemporary environment.
- Preserving healthy, natural tooth structure for as long as possible is conducive to optimal, long-term oral health. Every effort should be made to prevent initial carious lesions through personal, professional, and community-based means. When early or questionable caries occur, serious consideration should be given to attempting to reverse the process through the use of fluoride, diet modification, oral antibacterial rinses, and personal and professional oral hygiene measures.
- In order to preserve the maximum amount of sound tooth structure, dental sealants or preventive resin restorations (conservative composite restorations), rather than amalgam, should be used as the treatment of choice for noncarious occlusal surfaces at risk of dental caries and a substantial portion of occlusal surfaces with questionable or incipient caries. In both the prevention and treatment of dental caries, the caries risk of the patient should be of paramount consideration.
- Dental amalgam is an effective restorative material for treating carious lesions commonly encountered in dental practice. Amalgam has superior physical characteristics, longevity, low cost, and ease of use compared to alternative restorative materials. The extent and site of the carious lesion and the amount of tooth structure removal that would be necessary to properly restore the tooth are key, but not sole, determinants of whether alternative materials may be appropriately used in a given situation.
- When alternative materials to dental amalgam can achieve equivalent or greater preservation of sound tooth structure, similar clinical serviceability, and possibly enhance esthetics, at comparable long-term costs, they should be considered. Currently available alternative materials can serve only in a limited number of specific situations for restoring posterior teeth. Composites can be employed successfully in conservative posterior restorations that do not involve stress-bearing areas. Composites offer the advantages of preservation of sound tooth structure, esthetics, and much lower cost than cast or ceramic restorations. However, they are technique-sensitive. Cast and ceramic restorations can offer strength, durability, good biocompatibility, and potentially excellent esthetics, but they are costly and can involve the removal of much healthy tooth structure. Glass ionomer cements provide reasonable esthetics and excellent bonding to tooth structure, but they are technique-sensitive and cannot be used in stress-bearing areas.
- The removal of any dental restoration should be based on sound scientific criteria. The extensive removal of dental restorations poses potential risks to the oral and general health of individuals. The removal of functional dental restorations will have significant cost implications for individuals and public programs.
- The oral health benefits of dental amalgam may be underestimated. Research suggests that many existing amalgam restorations are replaced not because the presence of recurrent caries has been confirmed but because of conditions such as surface corrosion or marginal ditching that do not threaten the health of the tooth. Organized dental programs, third-party payers, and dentists should consider repair of existing restorations, when clinically appropriate, rather than their complete removal and replacement.
- Because of the continuing rapid development of new dental restorative materials and methods, it is important for the dental profession to keep informed of developments in dental materials through review of scientific studies and reports prepared by professional and scientific groups and agencies. Product promotional information alone does not provide an adequate basis for determining the value of restorative materials in clinical practice.
- A reporting and surveillance mechanism for tracking the prevalence and nature of adverse reactions to dental materials, which would be easy and attractive for clinicians to use, should be established.
- Teaching programs, including undergraduate, graduate, and continuing dental education, should include comprehensive consideration of the biocompatibility and clinical indications of dental restorative materials, the importance of recording in patients' records the types of restorative materials used, and the importance of reporting known or suspected adverse reactions to dental restorative materials.
Recommendations for Research
The U.S. Public Health Service, as well as other Federal departments (the Department of Defense, the Department of Veteran Affairs), continues to sponsor and conduct research on dental amalgam and other restorative materials, and the National Institute of Dental Research Long-Range Research Plan for the Nineties points to areas of additional research interest in restorative materials. The following broad array of research recommendations was identified by the Ad Hoc Subcommittee on the Benefits of Dental Amalgam as important areas to pursue, based on a review of the relevant scientific literature conducted during development of this report.
- The longevity of all restorative materials in both permanent and deciduous dentitions, with separate assessments for posterior versus anterior restorations and intracoronal versus extracoronal restorations, should be documented.
- The nature and extent of the adverse reactions to restorative materials and procedures should be monitored.
- Research should continue to assess the prevalence and incidence of diseases, conditions, and circumstances that predispose dentitions to the need for restorations and replacement of restorations.
- Priority should be given to research efforts geared to preventing the initiation of dental caries and reversing early carious attacks or lesions where they occur.
- Development and testing of new diagnostic methods and improvement of existing methods for disease detection and detection of restoration failure are needed.
- Investigations should continue to develop new materials and to improve existing materials, including dental amalgam, that would limit the amount of tooth tissue that must be removed for restoration placement or repair.
- Materials that provide therapeutic benefits in preventing further dental caries, in addition to restoring the tooth to form and function, should be developed and tested.
- Patient and provider factors related to clinical decision making regarding the use of dental amalgam and other dental materials, such as cost, characteristics of materials, material preferences, and delivery issues, should be studied, as well as aspects of the patient-provider relationship.
- The distribution and frequency of various restorative dental materials used by the dental profession should be documented, including examination of the reasons for using new versus replacement or repaired restorations as related to the class and severity of the restoration.