The selection of the type of dental restorative material is dependent on many factors, among them the characteristics of the tooth itself, the patient, the dentist, and the material. The dentist must make this selection with great care because, in future years, those restorations needing replacement will result in the loss of increasing amounts of tooth structure. This sets up a cycle where the increasing cavity size limits the selection of the materials that may be used effectively. There are numerous factors to consider when restoring a tooth, e.g., the extent of the lesion, the strength of the remaining tooth structure, the preference of the dentist in using the material, and the financial cost of the procedure, both out-of-pocket costs borne directly by the patient and those covered by insurance. The Benefits Report (Appendix I) outlines additional factors involved in this decision making process. One of these factors is the additional costs of substituting other materials for dental amalgam. All of the alternative materials are more expensive than amalgam on a one-time basis as well as over the lifetime of an individual. The general use of the alternative dental materials instead of amalgam will result in markedly higher treatment costs. In fact, one model predicts that totally discontinuing the use of dental amalgam would increase costs by at least $12 billion the first year with the likelihood of the cost increasing in later years. Although the primary reason to restore a tooth is dental caries, there are other clinical situations that require restorations. Table 3 provides a summary of these conditions and additional information is contained in the Benefits Report.

In considering the characteristics of an ideal restorative material, it is apparent that no single material can fulfill all of the clinical needs. The characteristics of the ideal restorative material are described as fulfilling requirements applying to the:

• physical and mechanical properties of the material,
• technical features of the material from the perspective of the dental professional,
• patient factors of acceptability, and
• other clinical aspects that contribute to the material's effectiveness.

The interaction of these factors determines the longevity of the dental restoration. Figure 1 demonstrates the interaction of the three factors and specifies the elements within each of these areas. (For an in-depth discussion of the elements, see the Benefits Report in Appendix I.)