Assessment of Self-Adhesive Resin Composites: Nondestructive Imaging of Resin–Dentin Interfacial Adaptation and Shear Bond Strength

Abstract

Shear bond strength (SBS) and the interfacial adaptation (IA) of self-adhesive resin (SAR) composites to dentin were evaluated. Two SARs [Vertise Flow (VTF) and Fusio Liquid Dentin (FLD)] were evaluated and compared with a conventional restorative system [adhesive: OptiBond FL and composite: Herculite Précis (OBF/HP)]. Human third molars were used for SBS testing and IA imaging (n=7) using optical coherence tomography (OCT). Flattened dentin disks were prepared and the composites were applied into molds (2.4 mm diameter) that were positioned on dentin. Samples were subjected to SBS testing and OCT analysis, which considered an increase in signal intensity at the bonded interface as evidence of internal gaps. SBS data were analyzed by one-way analysis of variance and Tukey's test and IA data (% distribution of high brightness values) by Kruskal-Wallis and Dunn's test (p≤0.05). No statistically significant difference in SBS was observed between VTF (13.9±3.6 MPa) and FLD (11.3±3.2 MPa), whereas OBF/HP showed higher average strength (27.3±6.1 MPa). However, there was a statistically significant difference in IA when VTF (33.3%) was compared with FLD (1.2%) and OBF/HP (1.5%). The conventional restorative system exhibited superior SBS performance compared with SARs. However, the IA of FLD to dentin had values that were not significantly different from OBF/HP.

Effect of Dentin Surface Treatment Using a Non-Thermal Argon Plasma Brush on the Bond Strength of a Self-Adhesive Resin Composite

“…In the present study, Vertise TM Flow resulted in thin and sparse tags compared to a different study, where tags were partially branched [27]. Not only when measured immediately after application [28], but especially after aging [29,30], self-adhesive composites present significantly lower bond strengths than conventional composites that were applied with a bonding system in the etch-andrinse or self-etch technique.…”

Polymer-Based Direct Filling Materials

“…In those situations, the use of self-adhesive materials can actually be advantageous because it theoretically eliminates the adhesive step, leaving more space in the very conservative cavity preparation for the insertion of the more highly filled material to be used. At least one in vitro study of the interface between these materials and enamel and dentin has demonstrated an absence of etching of the surface in either substrates, demonstrating a limited interaction with smear-covered surfaces and aprismatic enamel, with a thin interaction area of only about 200 nm [96, 98]. This agrees with the findings of another in vitro study that demonstrated inconsistent resin tag formation with the use of two commercially available self-adhesive composites, as reflected in a decreased shear bond strength and increased microleakage [98, 99].…”

“…At least one in vitro study of the interface between these materials and enamel and dentin has demonstrated an absence of etching of the surface in either substrates, demonstrating a limited interaction with smear-covered surfaces and aprismatic enamel, with a thin interaction area of only about 200 nm [96, 98]. This agrees with the findings of another in vitro study that demonstrated inconsistent resin tag formation with the use of two commercially available self-adhesive composites, as reflected in a decreased shear bond strength and increased microleakage [98, 99]. The prior application of acid etching seems to improve the microleakage resistance of these materials, at least in vitro [97].…”

Trends in restorative composites research: what is in the future?

“…16 Notwithstanding, some chemical interaction with calcium from hydroxyapatite has been verified, suggesting that the retention relies not only on micro-mechanical interlocking. 17,18 Overall, studies agree that SACs exhibit lower bond strength values to dental tissues than conventional restorative systems (Table 2), 12,19,20,21,22,23,24 with a few exceptions where composites were tested on radicular dentin 25,26 Several studies suggest that pre-etching enamel and dentin with phosphoric acid significantly increases bond strength, as phosphoric acid removes the smear layer and enhances surface area. 8,9,19,27,28,29 Using a self-etch adhesive prior to the application of Vertise Flow significantly increased the dentin bond strength and reduced microleakage scores, when compared with the application of the SAC alone.…”