Rationale for designing cavity preparations.

Increased resistance to caries, increased dental awareness, superior diagnostic capabilities, better illumination, optical aids that significantly enhance vision, improved and standardized materials for restoration, and a deeper understanding of the caries process enable a far more conservative approach to tooth preparation. The dentist can concentrate on preserving as much sound tooth structure as possible with less attention being devoted to resistance and retention form that previously demanded in bulk restorations and massive channels and locks that are no longer appropriate. Although caries inhibitory effects have been shown with materials such as silicate cement, glass ionomers, and resins that leach fluoride, in general, dentists should not rely on restorative materials to inhibit the development of future decay. Characteristics of the carious lesion are unique for each tooth according to many factors centering around the plaque pattern for that tooth and not according to zones of natural susceptibility or immunity strictly dictated by morphology. Therefore, no single cavity preparation duplicated from a textbook is likely to be satisfactory for an individual tooth. Furthermore, novices learning the subject of cavity preparation often leave decalcified enamel when they attempt to replicate under clinical conditions that which they have learned in technique courses. This is the major invitation to future caries reappearing adjacent to restorations. Also, failure to duplicate the exact morphology of the tooth surface that has been replaced is likely to alter the pattern of plaque accumulation and create other caries prone areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Rationale for designing cavity preparations in light of current knowledge and technology.

No restorative material presently available is as good as supported tooth structure and it is unlikely that a usable dental restorative material with the physical properties of enamel will ever be developed. The purpose of cavity preparation is to remove carious material and preserve sound tooth structure. Any additional removal of tooth structure is necessary for the convenience of the operator or because of limitations of the restorative materials. Presently available esthetic restorative systems for nonfunctional areas and selected anterior functional areas allow for designing cavity preparations where the only two considerations are removal of caries (and unsupported enamel) and placement of retentive features. The problem of cavity design for restoration of functional surfaces is not answered easily, but there is reasonable hope that in the near future an esthetic restorative material will be available that has the strength and other necessary properties to serve in functional areas. There should be no specific "ideal" design for cavity preparation. Each defect should be custom designed to remove the caries or defect and perform the additional steps necessitated by the limitations of the operator or restorative material. As advocated by Black in one of his later publications, it is necessary to make mouth-by-mouth and tooth-by-tooth judgements concerning the most desirable outline form to be obtained.