Abstract
The aim of this study was to evaluate the effect of enamel and dentin surface treatment on the micro-shear bond strength of self-adhesive cement. Seventy-two extracted third molars had their crowns embedded in acrylic resin and worn to obtain a flat enamel or dentin surface. The enamel and dentin specimens were randomly assigned to 8 groups (n=12) that were based on surface treatment (11.5% polyacrylic acid solution or no treatment), substrate condition (wet or dry) and storage period (1 day or 90 days), and treated accordingly. Cylinders (1 × 1 mm) were fabricated using self-adhesive resin cement (RelyX U200) following the manufacturer's instructions. The specimens were stored in distilled water at 37 °C for either 1 day or 90 days and subjected to micro-shear bond strength test (EMIC DL 2000 at 0.5 mm/min). After this, the failure type of the specimens was determined. Data were subjected to statistical analysis (a=0.05). According to the results, the 11.5% polyacrylic acid application decreased the bond strength in both enamel and dentin samples. The moist groups showed higher bond strength than the dry ones, regardless of the substrate and surface treatment. Storage period did not influence bond strength. In conclusion, surface treatment with 11.5% polyacrylic acid and absence of moisture decreased the bond strength of the resin-cement (RelyU200), regardless of the storage period.
Highlights
Resin cements have been widely used for indirect esthetic restorative procedures [1,2]
In order to obtain the dentin substrate specimens, the crowns of other 24 teeth were sectioned perpendicular to the long axis of the tooth to remove the occlusal enamel and to expose the flat, middle-third dentin surface (24 dentin sections)
An interaction effect was found between treatment and substrate condition (p=0.0009)
Summary
Resin cements have been widely used for indirect esthetic restorative procedures [1,2] These materials require prevous treatment of the tooth surface, like acid etching, to remove the smear layer, demineralize the underlying dentin and facilitate the penetration of cement into the exposed collagen fiber net to form a hybrid layer [2,3]. Efficient, it is a very sensitive technique considering the number of involved variables: operator, substrate quality, used material and the room temperature [1,2]. This suggests that a certain chemical bond occurs through a chelating reaction between the acid monomers and the hydroxyapatite present in dental substrates [2,6,7,8,9,10]
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