Abstract
The objective was to evaluate the influence of active bonding applications (ABA) for different time intervals after selective dentin etching (SDE) for 3 s on the microtensile bond strength (μTBS) to dentin of two universal adhesive systems (UAs): one containing 2-hydroxyethyl methacrylate (HEMA) (Scotchbond Universal, SBU), and one that was HEMA-free (Prime&Bond Universal, PBU). Dentin bovine specimens were divided into four groups: self-etch as control (SE), SDE + ABA for 15 s (SDE15), SDE + ABA for 20 s (SDE20), and SDE + ABA for 25 s (SDE25). The μTBS test was performed after a water storage of 24 h and 6 months. Scanning electron microscopy (SEM) was used in order to examine the resin–dentin interface. For the PBU, the µTBS was significantly influenced only by the aging factor (p < 0.026). A statistically significant decrease in the µTBS after 6 months of aging was observed only for the SDE15 group. For SBU, µTBS was significantly influenced by the protocol application and the aging time (p ≤ 0.041). The groups SDE15, SDE20, and SDE25 achieved statistically significant higher values (after 24 h and 6 months). No considerable variances were noticed in the homogeneity and continuity of the hybrid layer (HL) among the groups. In conclusion, SDE and ABA improved the µTBS only of a HEMA-containing universal adhesive.
Highlights
The bonding mechanism of resin composites to the enamel and dentin are slightly dissimilar [1]
The μTBS of two different universal adhesive systems (UAs) to etched dentin was evaluated according to the following factors: (1) time intervals of active application at three levels: 15 s, 20 s, and 25 s; and (2) storage time at two levels (24 h and 6 months)
ΜTBS was found to be significantly influenced by the groups and aging factors (p ≤ 0.041), and the interaction between these factors was statistically significant, too (p < 0.001)
Summary
The bonding mechanism of resin composites to the enamel and dentin are slightly dissimilar [1]. Since enamel and dentin are dissimilar substrates, it is imperative to recognize how they impact the performance of adhesives [3]. Resin–dentin bonding is a critical point in which the demineralization of the dentin collagen matrix used as a scaffold for resin impregnation is accomplished in order to create a stable hybrid layer (HL) [4,5]. Ideal hybridization is produced after monomer infiltration and their subsequent polymerization within the collagen network, firmly anchoring the adhesive and the overlying restoration to dentin [6]. The adhesive–dentin bond strength can be influenced by numerous factors, such as the polymerization (time, mode, exposure), the dentin region used for bonding, the composition of the adhesive system, and the application mode [8,9]. It is important to consider that the ideal hybridization results in a reliable bond strength which is essential to improve bonding effectiveness [9]
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