Replacement risk of amalgam treatment modalities: 15-year results

Objectives: This paper reports on the replacement risk of different treatment modalities for Class II amalgam restorations in a clinical trial of 15 yearsʹ duration. Methods: The performance of 1117 conventional Class II amalgam restorations in a controlled, longitudinal study were analysed using logistic regression with a random component. Primary variables regarding replacement risk were the treatment modality (cavity wall treatments) and alloy (conventional versus high copper). Secondly, the operator, type of tooth and type of restoration (MO/DO vs MOD) were considered. Results: Over 15 years, 17% of the restorations were replaced (true failures). The application of copalite varnish or silver suspension and the type of alloy did not reduce the replacement risk. Reduced risks were observed by providing a 90° cavosurface angle combined with a cavity wall finish. The operator and the type of restoration determine replacement risk to a significant extent. Conclusions: Additional treatment modalities do not necessarily reduce replacement risks of Class II amalgam restorations within 15 years, while clinical variables affect the risk of replacement to a certain degree.