REVIEWdental restorations in permanent posterior teeth, and its variability; and to identify and examine factors (referred to as effect modifiers) influencing the durability of restorations. Method Conduct of the reviewThe review was conducted in general accordance with guidelines promulgated by the NHS Centre for Reviews and Dissemination (CRD), 126 and the Cochrane Collaboration. 127 An advisory group was formed at the outset to assist the principal researcher (NAA) and act as consultants to the project. The group consisted of the remaining authors of the current report whose collective knowledge was considered to cover the areas of relevant expertise. Its task was to decide the scope of the review and the specific questions to be addressed; to approve and finalise the protocol; to monitor progress in identifying studies and deciding on their suitability for inclusion (assessment of validity); to discuss the proposals for analysis of the material and completion of the review; and to agree the final report. A meeting of the group and principal researcher took place at each stage. In addition, advice and guidance was obtained from the Systematic Review Unit at the Institute of Child Health, University College London. Inclusion and exclusion criteriaResources were limited and it was necessary to place some constraints on the scope of the review. Evaluations of the clinical performance of Class I (occlusal) and Class II (mesial-occlusal, distal-occlusal, mesial-occlusal-distal) restorations in permanent teeth, the commonest type of conservative treatment, predominate in the literature. It was therefore determined that the review should be confined to an assessment of the longevity of simple amalgam, composite resin, glass ionomer and cast gold restorations of those two types. A simple restoration was defined as one not requiring any form of additional retention measures. Search strategyThrough a comprehensive search, an attempt was made to identify all relevant studies irrespective of language. Available electronic databases, MEDLINE, EMBASE, CINAHL, DISSERTATION ABSTRACTS and ERIC were searched from their date of inception together with ISTP. Conference proceedings were searched using the citation index SCISEARCH. The subject headings or key components used included dental restoration, longevity, failure, durability, survival analysis, and life table analysis. In addition, the Cochrane Controlled Trials Register (CCTR) in the Cochrane Library (1998 Issue 2) was scrutinised for any relevant trials and cross checked with those already retrieved.Bibliographies of research reports identified through the search Objective To conduct a systematic review of the literature on the longevity of routine dental restorations in permanent posterior teeth, and to identify and examine factors influencing its variability. Method Accepted guidelines were followed. An advisory group oversaw the project. Simple Class I and Class II amalgam, composite resin, glass ionomer and cast gold restorations were covered. Comprehensive searchin...