Effect of HEMA on bonding of Er:YAG laser-irradiated bovine dentine and 4-META/MMA-TBB resin

Summary The purpose of this study was to evaluate the priming effect of 2‐hydroxyethylmetaclirate (HEMA) following acid treatment on resin bonding to prototype Er:YAG laser‐irradiated dentine. Extracted bovine dentine following laser irradiation was acid treated by aqueous solution of 10% citric acid (10‐0) or 10% citric acid/3% ferric chloride (10‐3), and additionally treated with 35% HEMA. Pre‐treated dentines were bonded to the polymethyl‐methacrylate (PMMA) rod with 4‐META/MMA‐TBB resin (Super Bond C & B) and miniaturized dumbbell‐shaped bonded specimens were prepared. These specimens profiled for tensile bond testing and fractured surfaces were observed by scanning electron microscopy (SEM). Cross‐sections of resin–dentine interface were also examined. The HEMA treatment following acid conditioned by 10‐3 or 10‐0 for both laser‐irradiated and non‐irradiated dentines was significantly higher than that without HEMA treatment. SEM view of a fractured specimen showed some cohesive failure in cured resin, but almost all of the fractured surface shows boundary failure between the penetrated resin and underlying dentine. A cross‐sectional view of the interface showed a very thick hybrid layer between the hybridized dentine and underlying dentine. It was concluded that HEMA treatment following acid conditioning provided a slightly higher bond strength for both the Er:YAG laser‐irradiated and non‐irradiated dentines. However, the bond strength of Er:YAG laser irradiated dentine was significantly lower than that of the non‐irradiated dentine.