Effects of Thermocycling on the Tensile Bond Strength between Resin Cement and Dentin Surfaces after Temporary Cement Application

Purpose: In a previous study the authors found that 2 of 3 tooth conditioners examined were able to reduce the negative effect of temporary cement on the bond strength between resin cement and teeth. The aim of this study was to evaluate the bond durability with the conditioners, as well as their capability for temporary cement dissolution. Materials and Methods: After eliminating the temporary cement with a curette from the bovine dentin surface, a conditioner (ethyl dihydrogen phosphate, EP; or methacryloxyethyl dihydrogen phosphate, MEP) was applied to the surface and a resin cement was adhered. Tensile bond strength measurement, scanning electron microscopic observation, and energy-dispersive analysis were carried out without thermocycling and after thermocycling. Results: The tensile bond strength gradually decreased with an increase in the number of thermocycles. However, specimens treated with EP or MEP showed significantly higher tensile bond strength values compared to those that did not receive conditioner application (P < 0.0001); EP showed significantly higher tensile bond strength values compared to the specimens that did not receive both temporary cement and conditioner application (P < 0.0001). The scanning electron microscopic, energy-dispersive, and solubility analyses suggest that both conditioners have the capability of dissolving temporary cement remnants. Conclusion: Both EP and MEP have potential value as conditioners to reduce the negative effect of temporary cement on the bond strength between resin cement and dentin and to improve the bond durability.