Effects of primer containing silane and thiophosphate monomers on bonding resin to a leucite-reinforced ceramic.

Silane primers are commonly used for bonding between resin-based luting agents and ceramic restorations. The purpose of the present study was to evaluate the effects of nine silane primers on the bond strength of resin to a leucite-reinforced ceramic. The commercially available dental primers used were five silane primers (GC Ceramic Primer, GP; Clearfil Ceramic Primer, CP; Tokuso Ceramic Primer, TP; Porcelain Liner M, PM; and Monobond Plus, MB). Four experimental primers (MDS, MTS, MDS/MPII, and MTS/MPII) and two control primers (MMA and MMA/MPII) were also prepared. The ceramic specimen was ground with silicon carbide paper, primed, and then bonded to a resin composite disc using a dual-curing luting agent. After a 24-h immersion in water, the shear bond strengths were determined. Shear bond testing revealed that the bond strength was significantly improved with the use of a MTS/MPII primer when compared to MDS, MTS, MMA, MDS/MPII and MMA/MPII. Although no significant differences were detected between GP, CP, PM, and MB, the primers CP, TP, PM, and MTS/MPII exhibited the highest bond strengths, followed by GP and MB, whilst the no-primer control resulted in the lowest values. The maximum bond strengths were obtained with CP, TP, PM, and MTS/MPII. It was suggested that the thiophosphate monomer accelerated the role of the silane monomer. When selecting a primer to bond ceramic restorations, clinicians should be aware that not only the silane monomer but also additional components of the primer considerably affect the bond strength.