Microtensile bond strength and morphological evaluations of total-etch and self-etch adhesives to caries-affected dentin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the microtensile bond strength and bond interface of total-etch or self-etch adhesives to normal dentin and caries-affected dentin.</p><p><b>METHODS</b>A total of 20 molars with occlusal caries lesion were used. The caries-affected dentin was obtained by removing the caries-infected dentin under the guidance of the caries detector. Beyond the level of caries-affected dentin all the enamel and partial dentin were removed. The adhesive systems, two total-etch adhesives (All-Bond 2, Prime&Bond NT) and two self-etch adhesives (Clearfil SE Bond, Xeno III) were applied respectively under the instructions of manufacturers. A block of composite resin was build up superficially. All the teeth were sectioned to obtain bar-shaped specimens with bonded surface area about 0.9 mm x 0.9 mm. The specimens were divided into normal dentin group and caries-affected dentin group via stereomicroscope. The bond strength was tested in a microtensile tester with a crosshead speed of 1 mm/min. The mean values of bond strength were compared using two-way ANOVA. The bonding interface between the dentin and adhesives was qualitatively evaluated under the observation of scanning electron microscope (SEM).</p><p><b>RESULTS</b>Two-way ANOVA revealed a significant influence of both the type of dentin and the adhesive systems tested on microtensile bond strength values. All the adhesives attained higher strength in normal dentin. In normal dentin, there was no significant difference between total-etch and self-etch adhesives. In caries-affected dentin, bond strength of Xeno III was significantly lower than the others. For SEM, the hybrid layer in caries-affected dentin was thicker but more porous than that in normal dentin. Compared with normal dentin, there was fewer resin tag exhibited in caries-affected dentin and no lateral branches were observed.</p><p><b>CONCLUSIONS</b>The total-etch adhesive had higher bond strength than self-etch adhesive systems in caries-affected dentin.</p>

Effects of residual water on microtensile bond strength of one-bottle dentin adhesive systems with different solvent bases / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The wet-bonding technique is recommended for the one-bottle dentin adhesive systems, but the moisture concept varies widely among the instructions of manufacturers as well as among investigators. The aim of this study was to evaluate the effects of different dentin surface moisture on the microtensile bond strength(s) of an ethanol/water-based adhesive system and an acetone-based system to dentin.</p><p><b>METHODS</b>Forty intact human premolars extracted for orthodontic reasons were used. Superficial occlusal flat dentin surfaces of these premolars were exposed, finished with wet 600-grit silicon carbide paper. Under four wet and dry conditions (overwet, blot dry, one-second dry and desiccated), resin composite was bonded to dentin by using Single Bond (SB) or Prime & Bond NT (PB) according to the manufacturers' instructions. The teeth were longitudinally sectioned in the "x" and "y" directions to obtain bonded beams with a cross-sectional area of 0.81 mm(2) with a slow-speed diamond saw. The bonded specimens were tested in tension at a crosshead speed of 1 mm/min until failure of the bonds. Failure modes were observed with a scanning electron microscope. The mean bond strengths were analyzed by one-way ANOVA and Turkey's test.</p><p><b>RESULTS</b>The bond strength of the overwet/SB, blot dry/SB, one-second dry/SB and desiccated/SB groups was 10.87 MPa, 22.47 MPa, 24.91 MPa and 12.99 MPa, respectively. The bond strength of the overwet/PB, blot dry/PB, one-second dry/PB and desiccated/PB groups was 10.02 MPa, 20.67 MPa, 21.82 MPa and 10.09 MPa, respectively. For both SB and PB, the blot dry group and one-second dry group revealed significantly higher bond strengths than the overwet and desiccated groups (P < 0.05).</p><p><b>CONCLUSIONS</b>In order to achieve the highest bond strength to dentin, keeping the dentin surface in an appropriately moist condition is critical for the one-bottle dentin adhesive systems with ethanol/water or acetone solvent.</p>

Microtensile bond strengths of three dentin adhesive systems / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate in vitro the microtensile bond strengths of three dentin adhesive systems and their respective fracture modes.</p><p><b>METHODS</b>A total of 15 intact young human premolars extracted for orthodontic reasons were used. The enamel of occlusal surfaces of these premolar teeth was removed and superficial dentine was exposed, finished with wet 600-grit silicon carbide paper. And then these teeth were randomly divided into three groups. A block of composite resin was bonded respectively with three dentin adhesive systems: All-bond 2 (Group AB(2)), Fluoro-Bond (Group FB) and Xeno III (Group Xeno) according to manufacturers' instructions. The bonded teeth were kept in distilled water for 24 h at 37 degrees C. The roots were removed from the remaining crown approximately 1 - 2 mm below the cemento-enamel junction with a slow-speed diamond saw. The teeth were sectioned to obtain bar-shaped specimens, whose bonded surface areas were about 0.8 mm(2). The specimens were stressed at a crosshead speed of 1 mm/min until rupture of the bond. SEM was used to observe the fracture modes. The mean bond strengths were compared using one-way ANOVA and LSD tests. The frequency of fracture modes was compared using Krukal-Wallis and Mann-Whitney U-test.</p><p><b>RESULTS</b>Mean microtensile bond strengths were (29.56 +/- 5.47) MPa for Group AB(2), (15.81 +/- 7.67) MPa for Group Xeno, and (14.61 +/- 4.50) MPa for Group FB. The bond strength of Group AB(2) was greater than those of the other two groups (P < 0.01). The bond strengths of Group Xeno and Group FB were not significantly different. SEM examination indicated that the adhesive failure was the most mode of fracture.</p><p><b>CONCLUSIONS</b>The microtensil bond strengths of three dentin adhesive systems to normal human dentine were different and the total-etching adhesive All-Bond 2 exhibited the greatest bond strength. It was recommended that dentin adhesive agent should be used according to clinical situation.</p>