Influence of Long-term Water Storage and Thermocycling on Shear Bond Strength of Glass-Ionomer Cement to Er:YAG Laser-prepared Dentin

Purpose: To evaluate the influence of long-term water storage and thermocycling on the shear bond strength of a glass-ionomer cement to Er:YAG-irradiated and bur-prepared dentin. Materials and Methods: Fifteen bovine incisors were selected and the roots removed. Crowns were sectioned into four pieces, resulting in 60 samples that were individually embedded in polyester resin (n = 15) and ground to plane the enamel and expose the dentin. The bonding site was delimited and samples were randomly assigned according to the method of cavity preparation: Er:YAG laser (250 mJ/4 Hz) or high-speed handpiece (diamond bur #2096). Samples were fixed to a metallic device, where glass-ionomer cement (GIC) cylinders were prepared. Subsequently, they were subdivided according to the duration of water storage (WS) and number of thermocycles (TCs) - 24 h WS/no TCs and 6 months WS/12,000 TCs - and subjected to a shear bond strength test (500 N at 0.5 mm/min). Results: The duration of water storage and number of thermocycles tested had no statistically significant effect on the shear bond strength to laser-irradiated dentin (p > 0.05). For bur-prepared substrate, the long-term degradation process promoted a decrease in shear bond strength values (p 0.05). Conclusion: Long-term water storage and thermocycling did not affect shear bond strength of glass-ionomer cement bonded to Er:YAG laser-prepared dentin. Keywords: glass-ionomer cement, shear bond strength, Er:YAG laser, dentin