Long-term evaluation and rerestoration of amalgam restorations.
In this study, 1544 class-II amalgam restorations were made and evaluated for 10 yr and the reasons for rerestoration were registered. Two categories of failure could be established: failures due to poor restorative technique (true failures) and those not due to poor restorative technique (false failures). After 10 yr, 1415 restorations were evaluated. Only 120 restorations (8.5%) had been replaced, most of these replacements being true failures (105 = 87.5%), which could be divided into: isthmus fracture (37), fracture of the enamel cusp (25), recurrent caries (16), partial fracture of the restoration (9), severe marginal breakdown (5), pulpal pathology (7) and others (6). The false failures (15) could only be classified into: caries elsewhere in the tooth (15). Origins of the true failures were the operator, the material (amalgam) and the type and size of the restoration. In this study, there were significantly more replacements of larger restorations than of smaller ones and more replacements in molars than in premolars. There is also a significant difference among the replacements by the various operators but not between the various types of amalgam. Origins of the false failures seem to be more related to patient factors like caries activity, caries susceptibility and oral hygiene, but chewing habits (bruxism) may also play a role.