Bond Strength and Cytotoxicity of a Universal Adhesive According to the Hybridization Strategies to Dentin

Abstract

This study evaluated application protocol (etch-and-rinse/ER and self-etching/SE) and dentin wettability (wet and dry) on microtensile bond strength (mTBS) and transdentinal cytotoxicity of Scotchbond TM Universal (SU) adhesive system. The mTBS values and fracture mode were registered 24 h after adhesive system application and resin composite block build-up (n=5). For analysis of transdentinal cytotoxicity, odontoblast-like MDPC-23 cells were seeded on pulpal surface of dentin discs (0.4 mm thick) adapted to artificial pulp chambers (n=8). The adhesive system was applied to occlusal surface, followed by 24-h incubation time. Cell viability (Alamar Blue) and morphology (SEM) were assessed. Adper Single Bond 2 and Clearfil SE Bond were used as positive controls of the ER and SE application protocols, respectively. No treatment was performed on negative control (NC) group. Data were analyzed by ANOVA and Tukey's tests (α=5%). Higher mTBS values were found for ER mode in comparison with SE protocol (p<0.05). Dentin wettability had no effect on bond strength of SU in both the ER and SE techniques (p>0.05). Most fractures involved hybrid layer and/or adhesive layer. Neither variable prevented the intense toxic effects of adhesive systems on MDPC-23 cultured cells, since intense reduction in cell viability (±88%) and severe alterations in cell morphology were observed for all groups compared to NC, with no differences among them (p>0.05). Therefore, it was concluded that application of SU following the ER protocol had better adhesive performance. However, this adhesive system featured intense transdentinal cytotoxicity to pulp cells, regardless of application protocol and dentin wettability.

Micro‐shear bond strength of adhesives with different degrees of acidity: Effect on sound and artificially hypermineralized dentin

“…The purpose of adhesive dentistry is to obtain a high quality (Leite et al, ; Van Meerbeek et al, ), stable, retentive dentin bond with marginal seal and clinical durability (Breschi et al, ); its technical improvements have significantly influenced modern dentistry (Cardoso et al, ).…”

“…They have reduced clinical stages and, consequently, reduced technical sensitivity (Burrow & Tyas, ; Florescu et al, ; Van Meerbeek et al, ; Yoshida et al, ), and therefore are considered “friendly adhesion systems.” These materials have hydrophilic and hydrophobic monomers and solvents in their composition, facilitating the diffusion of resin monomers into the conditioned dentin (Costa et al, ; R. Wang et al, ). Their acid monomers demineralize and infiltrate the dentin surface simultaneously, and depending on their pH, at the same depth (Florescu et al, ; Frassetto et al, ; Leite et al, ; Van Meerbeek et al, ; R. Wang et al, ; Y. Wang & Spencer, ). This allegedly improves the adhesive effectiveness (Frassetto et al, ) as it avoids nanoinfiltration, which can occur as a result of the discrepancy between demineralization and infiltration, especially in total‐etch adhesive systems (Breschi et al, ; Frassetto et al, ; Y. Wang & Spencer, ).…”

“…This allegedly improves the adhesive effectiveness (Frassetto et al, ) as it avoids nanoinfiltration, which can occur as a result of the discrepancy between demineralization and infiltration, especially in total‐etch adhesive systems (Breschi et al, ; Frassetto et al, ; Y. Wang & Spencer, ). The acidic monomers dissolve the smear layer, yet do not remove it, remaining together with the hybrid layer (Cardoso et al, ; Florescu et al, ; Leite et al, ). The hybrid layer produced by these adhesive systems depends on the demineralization capacity of their acid monomers (Cardoso et al, ; R. Wang et al, ).…”

“…Despite the reduced number of steps, restoration longevity can be compromised, compared to total‐etch adhesive systems. This is especially true when using one‐step, self‐etching adhesive systems (Leite et al, ; Van Meerbeek et al, ), which present reduced immediate adhesion strength compared to two‐steps adhesive systems (Van Meerbeek et al, ). The performance of these materials is dependent on their composition and the functional monomer they include (R. Wang et al, ).…”

“…Direct composite resin restorations are commonly used in dentistry; their success depends on the effectiveness of the adhesion between the dental substrate and restorative material (Leite, Costa, Duarte, Andrade, & Soares, ; Van Meerbeek et al, ).…”