Thermocycling, silane priming, and resin/porcelain interfaces interfaces--an electrical leakage study.

High 24-hour tensile and shear bond strengths have been reported for silane-primed resin/porcelain interfaces, but bonds often failed after prolonged water storage. This study was designed to determine the influences of both a silane primer and thermocycling on interfacial leakage between a light-cured BisGMA resin and dental porcelain. Porcelain discs measuring 10 mm in diameter and 1.5 mm in thickness were fired. Axial cylindrical cavities were prepared through the discs with a diamond bur. Four groups of eight discs each were restored in the following modes: groups 1 and 2 with light-cured bonding agent and light-cured microfilled resin, and groups 3 and 4 with a silane primer followed by the same bonding agent and resin. Specimens were water-stored for 24 hr, after which those in groups 2 and 4 were thermocycled 200 times between 4 degrees C and 60 degrees C. Specimens were then sealed to steel anodes and placed in 1% KCl, maintained at 21 degrees C, around a stainless steel cathode. Leakage currents were recorded daily for 30 days and after six months, by application of a 10 V potential difference between the cathode and each anode. Positive and negative controls gave massive and nil readings, respectively. The mean leakages were consistently greatest in group 2 (being significantly greater than for the other groups). Results suggest that silane priming minimizes leakage at the resin/porcelain interface after thermal cycling.