Abstract
The purpose of this study was to evaluate the influence of the application mode of three universal adhesive systems on interfacial physical properties of indirect composite restorations adhesively cemented to dentin cavities. Seventy-eight bovine lower incisors were selected and a slice of dentin (thickness: 2 mm) between the buccal surface and pulp chamber was obtained for each tooth. Conical cavities were made on this surface. The internal walls of the cavities were then coated with a hydrophilic gel, filled with composite resin and photopolymerized. The dentin/cone sets were divided into 6 groups (n=10) according to type of universal adhesive (TETRI: Tetric N Bond, FUT: Futura Bond U, SBU: Single Bond Universal) and acid etching on dentin (A: with acid etching; WA: without acid etching). The acid etching and the adhesive systems were applied to the surface of the dentin. All composite resin cones were sandblasted (Al2O3, 20 s) and silanized. After surface treatment, the cones were cemented (RelyX Ultimate) into the dentin cavity and photopolymerized. After thermocycling (10,000 cycles), samples were submitted to marginal adaptation analysis (using caries detector dye), push-out test (0.5 mm/min), and failure mode analysis. Additional samples were prepared for nanoleakage analysis (SEM). The data (MPa) were analyzed by two-way ANOVA and Tukey's post-test (5%). The groups in which the dentin was acid etched showed significantly lower bond strength values in the push-out test (p<0.01). Dentin acid etching significantly reduced the bond strength between universal adhesive systems and dentin in indirect restorative procedures.
Highlights
Direct composite resin restorations, as well as indirect or semi-direct restorations [1] have been an option in dental practice
Push-Out Bond Strength The results indicated that the data were normally distributed (p>0.05)
The influence of acid etching on the bond strength between three universal adhesive systems and bovine dentin was investigated
Summary
As well as indirect or semi-direct restorations [1] have been an option in dental practice. Indirect and semi-direct techniques overcome some of the disadvantages of direct restorations, such as polymerization shrinkage and the cementation “gap”(1). These restorations have better mechanical properties due to the additional polymerization with light or heat, lower microleakage, lower costs, and easier intraoral maintenance compared to dental ceramics [1]. In spite of the excellent longevity, problems related to dentin adhesion have been reported [4] Some factors, such as overdrying of dentin after acid etching, excess moisture, and excessive acid demineralization or acid undercorrosion, may decrease the flow of resinous monomers along the intertubular dentin, compromising the longevity of restorations [5]. The conventional approach for adhesive restorations, including dentin etching with phosphoric acid (35-37%), is an established and predictable clinical procedure, the acid corrosion of dentin is a definitive factor for adhesion quality, increasing wettability and surface roughness, and allowing the penetration of adhesives and resin cements through the smear layer [4]
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