Repair of an aged, contaminated indirect composite resin with a direct, visible-light-cured composite resin

This study investigated the interfacial shear bond strength of a contaminated, aged, heat- and pressure-processed, indirect composite resin (Concept) repaired with a direct, visible-light-cured composite resin (Heliomolar). Concept samples were aged by thermocycling and contaminated in tobacco juice. The bonding surfaces were prepared by sanding with 500-grit sandpaper or air abrading with 50-micron aluminum oxide. Prepared Concept surfaces received one or more of the following intermediary resin treatments before the addition of Heliomolar: Heliobond, Special Bond 2, All-Bond system, All-Bond bonding agent, or no bonding agent, and they were immediately thermocycled. Air abrasion produced significantly higher bond strengths than sanding for all intermediary resin surface treatments. The All-Bond-treated Concept surfaces showed the highest interfacial bond strengths within the air abraded and sanded groups. Visual and SEM examination of fractured repair surfaces indicated adhesive failure within all treatment groups.