The present study determined the mechanical properties and impact-sliding wear characteristics of self-adhesive resin cements. Five self-adhesive resin cements were used: G-CEM LinkAce, BeautiCem SA, Maxcem Elite, Clearfil SA Automix, and RelyX Unicem 2. Clearfil Esthetic Cement was employed as a control material. Six specimens for each resin cement were used to determine flexural strength, elastic modulus, and resilience according to ISO specification #4049. Ten specimens for each resin cement were used to determine the wear characteristics using an impact-sliding wear testing apparatus. Wear was generated using a stainless-steel ball bearing mounted inside a collet assembly. The maximum facet depth and volume loss were determined using a noncontact profilometer in combination with confocal laser scanning microscopy. Data were evaluated using analysis of variance followed by the Tukey honestly significantly different test (α=0.05). The flexural strength of the resin cements ranged from 68.4 to 144.2 MPa; the elastic modulus ranged from 4.4 to 10.6 GPa; and the resilience ranged from 4.5 to 12.0 MJ/m(3). The results for the maximum facet depth ranged from 25.2 to 235.9 μm, and volume loss ranged from 0.0107 to 0.5258 mm(3). The flexural properties and wear resistance were found to vary depending upon the self-adhesive resin cement tested. The self-adhesive cements tended to have lower mechanical properties than the conventional resin cement. All self-adhesive resin cements, apart from G-CEM LinkAce, demonstrated significantly poorer wear resistance than did the conventional resin cement.

This study investigated the effect of a coating material containing S-PRG fillers on the demineralization of bovine enamel and dentin, by measuring changes in the transmitted ultrasonic velocity. Bovine enamel and dentin specimens with and without coating (n=6 for each condition) were cut into blocks, immersed in 0.1 M lactic-acid buffer solution (pH 4.75) for 10 min twice daily throughout the test period, and stored in a demineralising artificial saliva solution (pH 7.0) between treatments. The propagation time of longitudinal ultrasonic waves was measured by a pulser-receiver with a transducer. Data were evaluated using ANOVA followed by Tukey's HSD test (α=0.05). The sonic velocity decreased over time for specimens stored in demineralising solution; however, coated specimens had a significantly higher sonic velocity than those without coating. The coating material containing pre-reacted glass-ionomer fillers therefore appeared to reduce the demineralisation of enamel and dentin.

The purpose of this study was to determine the influence of surface treatment of glass-ionomer (GIC) on bond strength of resin composite and surface free energies. Specimens were prepared and divided into three groups as follows: without pretreatment (control), phosphoric acid etching, and air-abrasion. Adhesive was applied and resin composite was bonded. For conventional GIC, acid etching or air-abrasion increased bond strength (8.5-8.8 MPa) when compared with controls (4.7 MPa); however, RMGIC resulted in significantly lower bond strengths (10.3-15.8 MPa) than in controls (14.2-20.5 MPa). The value of the γ S − component increased when conventional GIC was treated with phosphoric acid or air-abrasion (60.1-60.5 mJ•m −2 ) when compared with controls (52.8 mJ•m -2 ). These results indicate that surface treatment of conventional GIC promoted higher bond strength to resin composite and higher Lewis-base components, but decreased bond strength for RMGIC.

SUMMARY Objective We examined the influence of light intensity on surface free energy characteristics and dentin bond strength of dual-cure direct core build-up resin systems. Methods Two commercially available dual-cure direct core build-up resin systems, Clearfil DC Core Automix with Clearfil Bond SE One and UniFil Core EM with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in acrylic resin and the facial dentin surfaces were wet ground on 600-grit silicon carbide paper. Adhesives were applied to dentin surfaces and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm2. The surface free energy of the adhesives (five samples per group) was determined by measuring the contact angles of three test liquids placed on the cured adhesives. To determine the strength of the dentin bond, the core build-up resin pastes were condensed into the mold on the adhesive-treated dentin surfaces according to the methods described for the surface free energy measurement. The resin pastes were cured with the same light intensities as those used for the adhesives. Ten specimens per group were stored in water maintained at 37°C for 24 hours, after which they were shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. Two-way analysis of variance (ANOVA) and a Tukey-Kramer test were performed, with the significance level set at 0.05. Results The surface free energies of the adhesive-treated dentin surfaces decreased with an increase in the light intensity of the curing unit. Two-way ANOVA revealed that the type of core build-up system and the light intensity significantly influence the bond strength, although there was no significant interaction between the two factors. The highest bond strengths were achieved when the resin pastes were cured with the strongest light intensity for all the core build-up systems. When polymerized with a light intensity of 200 mW/cm2 or less, significantly lower bond strengths were observed. Conclusions The data suggest that the dentin bond strength of core build-up systems are still affected by the light intensity of the curing unit, which is based on the surface free energy of the adhesives. On the basis of the results and limitations of the test conditions used in this study, it appears that a light intensity of >400 mW/cm2 may be required for achieving the optimal dentin bond strength.

The purpose of this study was to determine the effect of PRG filler extraction solution on the demineralization of enamel using optical coherence tomography (OCT). Bovine enamel was treated with lactic acid buffer solution and then placed in artificial saliva (De group). In the second group, specimens were stored in PRG filler extraction solution followed by immersion in lactic acid buffer solution (PRG group). In the control group, specimens were simply stored in artificial saliva. From the OCT image, the peak intensity (dB) and width at (1/e 2 ) were obtained, and the integrated value was calculated. The data were analyzed using Tukey-Kramer tests (α=0.05). There was a slight but significant increase in the integrated value observed for the control group, and a slight but significant decrease in the value observed for the De group. For the PRG group, integrated values were doubled after seven days from the start of the experiment.