Abstract
Objectives:To evaluate the microtensile bond strength (μTBS) of one- (Xeno III, Dentsply) and two-step (Tyrian-One Step Plus, Bisco) self-etching adhesive systems bonded to dentin and cemented to chemically cured (C&B Metabond) or light-cured paste of a dual-cure resin cement (Variolink II, Ivoclar) within a short (24 h) and long period of evaluation (90 days).Material and Methods:Forty recently extracted human molars had their roots removed and their occlusal dentin exposed and ground wet with 600-grit SiC paper. After application of one of the adhesives, the resin cement was applied to the bonded surface and a composite resin block was incrementally built up to a height of 5 mm (n=10). The restored teeth were stored in distilled water at 37°C for 7 days. The teeth were then cut along two axes (x and y), producing beam-shaped specimens with 0.8 mm2 cross-sectional area, which were subjected to μTBS testing at a crosshead speed of 0.05 mm/min and stressed to failure after 24 h or 90 days of storage in water. The μTBS data in MPa were subjected to three-way analysis of variance and Tukey's test (α= 0.05).Results:The interaction effect for all three factors was statistically significant (three-way ANOVA, p<0.001). All eight experimental means (MPa) were compared by the Tukey's test (p<0.05) and the following results were obtained: Tyrian-One Step Plus/C&B/24 h (22.4±7.3); Tyrian-One Step Plus/Variolink II/24 h (39.4±11.6); Xeno III/C&B/24 h (40.3±12.9); Xeno III/Variolink II/24 h (25.8±10.5); Tyrian-One Step Plus/C&B/90 d (22.1±12.8) Tyrian-One Step Plus/VariolinkII/90 d (24.2±14.2); Xeno III/C&B/90 d (27.0±13.5); Xeno III/Variolink II/ 90 d (33.0±8.9).Conclusions:Xeno III/Variolink II was the luting agent/adhesive combination that provided the most promising bond strength after 90 days of storage in water.
Highlights
Contemporary dentin adhesives are classified as threestep, two-step and one-step systems, depending on how the three cardinal steps of etching, priming, and bonding to tooth substrates are accomplished or simplified[22,25]
In addition to the problem of permeability of these adhesives, it is known that chemical composite resins containing tertiary amines as catalysts do not present good bond strength to most two-step total-etch adhesives and single-step self-etching systems
Because the present study focused the interactions between the materials that may affect the strength at the adhesive interface over time, the following null hypotheses were tested: (1) At 24-h storage, the bond strengths obtained with oneor two-step self-etching adhesives combined to chemically cured and light-cured cements are not different; (2) At 90-day storage, the bond strengths obtained with one- or two-step self-etching adhesives combined to chemically cured and light-cured cements are not different; (3) There are no differences in bonding durability between 24 h and 90 days of storage
Summary
Contemporary dentin adhesives are classified as threestep, two-step and one-step systems, depending on how the three cardinal steps of etching, priming, and bonding to tooth substrates are accomplished or simplified[22,25]. The two-step self-etching systems are userfriendly adhesives that mildly interact with the dentin substrate. In addition to the problem of permeability of these adhesives, it is known that chemical composite resins containing tertiary amines as catalysts do not present good bond strength to most two-step total-etch adhesives and single-step self-etching systems. In these adhesives, the acidic monomers in the oxygen-inhibited layer are brought in direct contact with the chemically cured composite, titrating the basic amine accelerators and inactivating them[5,10,20]
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