What is Known About Caries in Relation to Restorations as a Reason for Replacement? a Review

In the past 20 years, a great many studies have identified secondary caries to be the most common reason for the replacement of restorations. This review raises the question whether clinicians use 'secondary caries' as a catch-all into which they put a variety of reasons for replacement, or whether they do have professionally based reasons for focusing on caries adjacent to restorations. There is no consensus among researchers concerning the nature of secondary caries, but it is possible to identify two major-and conflicting-trends : One adheres to a critical approach concerning the frequency of replacements and recommends a much more conservative evaluation of existing fillings. In contrast, the other trend focuses on the clinical undetectable microleakage as the major risk factor for the initiation and uncontrolled dentinal spread of secondary caries. Since the latter trend offers a reasonable explanation for the clinicians' concern about invisible 'secondary caries', and hence reinforces the tendency to replacement, it is relevant to reconsider the conventional concept that microleakage leads to the initiation of secondary caries. Available data indicate that visible gaps and marginal discrepancies are poorly related to secondary caries, and that secondary caries is a localized phenomenon caused by localized conditions for the evolution of cariogenic plaque. Consequently, secondary caries is not a universal attack along the entire interface between tooth and restoration, but rather a new lesion or a re-beginning of caries on the surface due to local conditions for plaque formation with cariogenic potential. It is concluded that reinforcement of a new and more appropriate professional behavior should be based on diffusion of existing knowledge of dental caries as a disease rather than on simplified criteria for the placement and replacement of dental restorations.