Restoration deterioration related to later failure.

The purpose of this study was to determine the relationship between the deterioration and the later failure of a very large number of amalgams and anterior resin composites examined over periods of up to 16 years. Assessments were made of the deterioration of various clinical factors or characteristics of the restorative materials that were thought to predict later failures. True failures, which were directly related to the restorative materials, accounted for 7.5% of the amalgam and 30.4% of the composite restorations. For the amalgams, there was a significant association found between the failures and surface tarnishing. Marginal fracture and marginal staining were not associated significantly with any of the three different failure modes. For the composites there were significant associations found between the failures and surface roughness, marginal fracture, and color mismatch. Surface staining and marginal staining were not associated significantly with any of the three different failure modes. Many restorations assessed as being unsatisfactory continued to function for a further 2.5 to 3.5 years on average before being replaced, often for unrelated reasons. There is a need to define unsatisfactory restorations more clearly in terms of actual adverse effects on dental health, rather than merely in terms of restoration deterioration.