Abstract
Interfaces between dentin, enamel and luting agents were characterized using low vacuum Scanning Electron Microscopy (SEM). After smear layer creation, one of three luting agents (RelyX Unicem 2, Clearfil SA Cement and Panavia F 2.0/ED Primer II) was applied on 60 enamel-dentin specimens and dual-cured or self-cured. Specimens were polished (Experiment 1) and subsequently demineralized and deproteinized (Experiment 2). Adhesive interfaces were analyzed (low vacuum SEM, ×3000). Presence of an interdiffusion zone, tag-like structures (dentin) and marginal gaps (enamel) were assessed. Non-parametrical tests (χ2-test, α = 0.05) were performed. The first null-hypothesis was that the adhesive interface micromorphology between enamel and dentin and self-adhesive resin cements (SARCs) is similar with conventional resin cement used with a self-etch adhesive (CRC+SE). The second null-hypothesis was that the micromorphology is not influenced by curing modes. Interdiffusion zones and tag-like structures (dentin) were observed more frequently for CRC+SE compared to SARCs. For each luting agent, there was a non-significant (p > 0.05) tendency for interdiffusion zone and tag-like structures detectable in more specimens after self-curing compared to dual-curing. Marginal gaps (enamel) were found only for SARCs. The first null-hypothesis was not rejected fully: Tag-like structures and interdiffusion zones in dentin were found for CRC+SE and SARCs. The second null-hypothesis was not rejected.
Highlights
A sufficient and clinically reliable bond between dental tissues and restorations is a crucial precondition for resin bonded partial crowns, crowns, and bridges [1]
Self-adhesive resin cements (SARCs) are designed to combine the ease of use of glass ionomer cements and the favorable mechanical and adhesive properties of conventional resin cements in combination with a beforehand applied adhesive system (CRC+SE) [5]
The aim of this study was to enroll low vacuum scanning electron microscopy (LV-Scanning Electron Microscopy (SEM)) under low voltage conditions to visualize the micromorphology of the adhesive interfaces between human enamel and dentin, and three different luting materials: two SARCs used without a separately applied self-etch adhesive and one CRC+SE
Summary
A sufficient and clinically reliable bond between dental tissues and restorations is a crucial precondition for resin bonded partial crowns, crowns, and bridges [1]. While conventional resin cements like Panavia F 2.0 (Kuraray, Tokyo, Japan) require pretreatment of the tooth surface with acidic primers or self-etch adhesives, SARCs comprise acid-functionalized monomers that aim to directly demineralize and chemically interact with dental tissues by formation of calcium salts [6]. In order to obtain a stable bond between dentin and the SARC, interaction with the smear layer is crucial, for SARCs, which can be used clinically without etch-and-rinse pretreatment of the tooth surface [12]. A smear-layer with reduced thickness as produced by finishing instruments may lead to a higher dentin bond strength for mild self-etch adhesives or self-adhesive restorative materials compared to thicker smear-layers as produced by carbide-burs [13,14,15,16]
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