Resin Cements and the Microleakage of Bonded Amalgams

Objectives: Microleakage is a problem of amalgam restorations especially with the high copper amalgams where no or little corrosion products are formed.  To reduce microleakage, to increase retention and to support and strengthen cavity walls the bonding of amalgam restorations was introduced. This is achieved by applying a less viscous resin-based material to the walls of the cavity and to condense the amalgam in the cavity before hardening of the bonding material. The aim of this study was to determine the effect of resin cements used as bonding intermediates, as well as the effect of thermal stress on the microleakage of amalgam restorations. Methods: Class II butt joint cavities were prepared on the mesial aspects of 120 sound extracted human molar teeth. They were randomly divided into 3 groups of 40 each. The resin cements Duo cement and Rely X ARC were applied to two of these groups.  The third group was left untreated.  They were then further divided into two groups of 20 each and restored with Dispersalloy and Oralloy Magicap S respectively.  Ten specimens of each group were thermocycled. All the teeth were stored in Basic Fuchsin (0,5%), for 8 hours, sectioned and evaluated for dye penetration using a light microscope (40x magnification). The scores were tabulated and subjected to Fisher’s Exact test at a confidence level of 99%. Results: Microleakage of the non-bonded amalgams were significantly higher (p<0,001) than for the bonded amalgams under both thermocycling and non-thermocycling conditions. In general, microleakage was not significantly increased by thermocycling. The sealing ability of Duo cement did not differ significantly from Rely X. Conclusions: Within the limitations of this experiment, we conclude that by bonding amalgam restorations with resin cements, microleakage could be reduced. Furthermore, it was shown that thermal stress did not affect the bond adversely.