Influence of different adhesive protocols on ceramic bond strength and degree of conversion of resin cements

Since light-curing through ceramic dental restorations can be attenuated by the material crystalline structure, the use of specific adhesive protocols might enhance bonding effectiveness of dual-cure resin cements. This study evaluated the micro-shear bond strength (µSBS) of different adhesive protocols containing dual-cured resin cements bonded to two glass ceramics: fluorapatite leucite (FLC) and lithium dissilicate reinforced ceramic (LDC), and their effect on the degree of conversion (DC) of resin cements. For each ceramic, eight adhesive protocols were tested using combinations of three different resin cements and four adhesive resins. Following the adhesive resin application on ceramic disk surface, resin cement cylinders were produced. After 24 h, the µSBS test was performed (n=8), a shear load was applied at a crosshead speed of 0.5 mm/min until failure and fracture patterns were determined. Resin cement DC analysis was performed by Fourier Transform Infrared Spectroscopy (n=5). Data were statistically analyzed using two-way ANOVA, followed by Tukey test (α=0.05). The interaction of adhesive protocol and ceramic type significantly affected the micro-shear bond strength and resin cement DC (p<0.0001). For the FLC, adhesive protocols containing the conventional resin cement produced higher µSBS values compared to the remaining protocols. For the LDC, the combination of the conventional resin cement and an adhesive resin containing photoactivators produced higher µSBS compared to the other tested adhesive protocols. The conventional resin cement and the self-etch cement produced higher conversion values when luted to the LDC. Selection of specific adhesive protocols should be carefully considered to improve bonding to glass ceramics.