Effect of pre-cure temperature on the bonding potential of self-etch and self-adhesive resin cements

Objectives: To assess whether the pre-cure temperature of resin cements significantly influenced the bonding potential to dentin. Methods: Forty extracted molars were randomly divided into 8 groups (n = 5): Groups (1-4) RelyX Unicem (RU, 3 M ESPE) and Groups (5-8) Panavia F 2.0 (PF, Kuraray Co.), at pre-cure temperatures of 4, 24, 37, and 60 °C, respectively. Cements were used in dual-cure mode for luting composite overlays (Paradigm MZ100, 3 M ESPE) to dentin. Microtensile bond strength testing and scanning electron microscope (SEM) observations of cement-dentin interfaces were performed. Results: Group 4 had to be eliminated as RU at 60 °C underwent such an accelerated curing that was already set at the time of dispensing. The bond strengths (MPa) measured at refrigerator, room, and intraoral temperature were, respectively: RU 5.4 ± 1.7, 11.4 ± 6.1, 10.6 ± 4.2; PF 7.4 ± 3.7, 13.9 ± 6.2, 12 ± 5.2. The statistical analysis revealed that both luting agents developed a significantly weaker adhesion when used at refrigerator temperature (p < 0.05). No statistically significant differences in bond strength were recorded when either cement was used at 24 or 37 °C (p > 0.05). Pre-heating of PF to 60 °C resulted in a significant increase in bond strength (20.7 ± 9.4 MPa; p < 0.05). SEM observations disclosed an enhanced potential of PF to form a hybrid layer as the temperature increased over 4 °C. RU exhibited a less porous and more homogeneous layer at intraoral than at refrigerated temperature. Significance: It is advisable to let refrigerator-stored resin cements warm up to at least room temperature prior to clinical use. Pre-heating to 60 °C enhances the bonding potential of PF. © 2007 Academy of Dental Materials.