[Effect of sodium hypochlorite gel on shear bond strength and bond durability of excite to dentin]

Although bonding mechanism is based on resin diffusion onto the demineralized dentin collagen fibers in most of dentin adhesive systems, it has been shown that the bond is going to degrade over time. The aim of this study was to determine the effect of sodium hypochlorite on shear bond strength and bond durability of Excite to dentin. In an experimental study, buccal and lingual surfaces of 36 intact human premolars were prepared and randomly assigned to 4 groups. In groups 1 and 3, specimens were etched and bonding procedures were accomplished according to manufacturer's directions. Then, composite resin was bonded to the dentin surfaces. In groups 2 and 4, AD Gel [10% sodium hypochlorite gel] was applied in order to remove the collagen fibers after acid conditioning. Then, the bonding procedure was followed as for groups 1 and 3. After 24 hours, water storage in groups 1 and 2 and 1 year water storage in groups 3 and 4, shear bond strength was evaluated and analyzed by one way analysis of variance. Variance test was used for data analysis due to normal distribution of data and homogeneity of variances. ANOVA test showed that shear bond strength of group 1 [28.2 +/- 7.0 MPa] was significantly higher than group 2 [17.6 +/- 8.6 MPa] [P=0.001]. The bond strength was also significantly higher in group 3 [29.4 +/- 4.7 MPa] than group 4 [21.3 +/- 8.0 MPa] [P=0.009]. No statistical significant difference was found between groups 1 and 3 and also between groups 2 and 4 in terms of shear bond strength. Shear bond strength of Excite to dentin decreased with using sodium hypochlorite gel. Shear bond strength of Excite did not show any significant difference after one year of water storage, with or without using sodium hypochlorite gel

effect of glass - fibers on flexural strength of composite resins

The aim of this study was to evaluate the effect of glass-fiber on the flexural strength of composite resins. The study was done experimentally in which flexural strength of glass - fiber reinforced composite resins were assessed with a three-point load test on 22 samples. 11 samples of composite resin blocks and 11 samples of composite resins reinforced with glass - fiber were prepared in a mold of 25x6x2 mm and stored in 100% of moisture for one month, until they were ready for testing in an Instron Universal Testing Machine using a crosshead speed of 1 mm/min. Student t test was used for statistical analysis. Flexural strength in the first group was 22.39 +/- 3.38 MPa and in second group was 29.74 +/- 2.36 MPa. According to test analysis, the difference between the two groups was statistically significant. [P<0.01]. The results of this study suggest that the flexural strength of the fiber-reinforced composite made from glass - fibers was more than composite resin