A Systematic Review of Amalgam Bonded Restorations: In vitro and Clinical Findings

This article aims to systematically review the evidence reporting on physical properties of bonded amalgam, its clinical performance, and implications.

An electronic search in "Medline" (search term: Amalgam and Dentin bonding) from 1987 to 2013 yielded 465 publications out of which 170 articles were selected for the analysis. Data were extracted relating to the bond strength of amalgam to dentin, microleakage, postoperative sensitivity, and longevity of bonded amalgam restorations.

A total of 129 in vitro studies out of 170 articles showed high bond strengths with filled adhesive resins and light-cured adhesives, in particular Amalgambond plus and Optibond adhe-sives. Thickness of bonding agent, type of alloy, and thermo-cycling showed inconclusive outcomes between bonded and nonbonded amalgam restorations. Majority of studies reported reduced microleakage when dentin bonding agents and resin-modified glass ionomer cements (RM-GICs) were used with amalgam. However, water stored, thermocycled, and spherical amalgam alloys resulted in higher microleakage. While bonded amalgam facilitated the retention of large restorations, reduction in postoperative sensitivity was not consistently observed between bonded and nonbonded amalgam restorations.

While bonded amalgam restorations reduce the need for mechanical retention conserving tooth structure and reducing the adverse effects of microleakage, there is lack of consistent evidence across all outcome domains to advocate the benefit of bonding of all amalgam restorations. Despite this, it can be considered the material of choice for large restorations and bonding enhances retention in vitro which can be considered beneficial clinically.

The use of adhesives to bond amalgam to the tooth structure offers potential advantages, as it helps in conservative cavity preparation without compromising the retention to tooth, making it a material of choice in large posterior restorations.