Effect of the addition of thiourethane oligomers to experimental silanes and resin cement on the bond strength to glass ceramic

Background Despite advances in silane and resin cement formulations, the long-term stability of ceramic bonds remains susceptible to degradation, and strategies to enhance interfacial performance are still under investigation. This study aimed to evaluate the effect of incorporating thiourethane (TU) oligomers into silane or resin cement formulations on the microshear bond strength (μSBS) of ceramic restorations. Methods Experimental silanes and resin cements containing 0 or 20 wt% TU were formulated with dicyclohexylmethane-4,4′-diisocyanate and pentaerythritol-tetra-3-mercaptopropionate and applied to etched lithium disilicate ceramic plates. Nine combinations of silane and cement (10/group) were tested. μSBS was measured after 24 hours, 6 months, and 18 months of storage in water. Data were analyzed using 2-way analysis of variance and Tukey post hoc (α = 0.05). Results TU resin cement exhibited higher μSBS values than the commercial resin cement, particularly after 24 hours when combined with TU and methacrylate-based (MA) silanes, and after 6 months with the MA silane ( P < .05). When using the commercial silane, there was no difference in μSBS among the resin cements ( P > .05). However, the combinations of TU and MA silanes, along with TU and MA resin cements, exhibited significantly higher μSBS than other formulations ( P < .05). All groups showed a significant reduction in μSBS over time ( P < .05), with the TU resin cement maintaining higher values than the commercial resin cement. Conclusions The use of TU oligomers as silane or resin cement additives improves the μSBS of resin cement-ceramic interfaces, especially when TU silane is combined with TU resin cement (dicyclohexylmethane-4,4′-diisocyanate version). Water storage for 6 and 18 months significantly reduces μSBS across all groups.