This study has examined the influence of different materials and patient factors on restoration age at time of replacement/failure and the reasons why restorations are replaced. In common with other studies of this type, derived from the original work of Mjor, such research suffers a number of inherent limitations, some of which have previously been discussed. The participating practitioners received no formal training in their diagnoses of restoration failure, other than that given in their dental school training or from continuing education courses. The participating GDPs were asked to use their everyday clinical criteria in assessing each restoration. The diagnostic criteria used were therefore the same for each material, thus allowing comparison between the status of restorations formed in different materials in patients with different oral hygiene and caries susceptibility and under different arrangements for funding. This is ‘real life’ data from the arena of general dental practice, with its time and financial pressures, in which the dental health of the UK is principally placed. These data are not intended to substitute controlled clinical trial data, but rather supplement and complement them.