[Class I and II cavities for amalgam restorations]

In a Danish cross-sectional survey of replacements of fillings it was reported that a major reason for replacement of Class II amalgam restorations was bulk fractures (22). This initiated an examination of a sample of 168 Class II cavity preparations made by dentists from Denmark and other Scandinavian countries. The results showed that the Danish cavities were deepest occlusally and buccally, had the most converging proximal walls, and the broadest bucco-lingual outline occlusally. On the basis of the literature, it is not possible to evaluate the clinical significance of these differences and there is no distinct explanation why bulk fractures cause replacement of amalgam fillings more frequently in Denmark than in the rest of Scandinavia. Only a longitudinal clinical examination of the fillings may show whether the observed differences in the cavity preparations results in an increased frequency of isthmus fractures and are of importance for the longevity of the fillings.