[ effect of one versus two applications of self- etch primers on micro-shear bond strength to the enamel and dentin]

Self etch acidic primers may be unable to etch the enamel and penetrate the thick dentinal smear layer and as a result produce inadequate bond strength. The present study aimed to evaluate the effect of the second layer application of two self-etch primers on etching pattern and micro-shear bond strength to the enamel and dentin. In an experimental study, 104 human premolar teeth were divided into two groups. The buccal surfaces of the teeth were prepared for enamel and dentinal evaluation. Self-etch primer of clearfil SE Bond and clearfil S3 Bond were applied in one or two layers on the prepared enamel and dentin surfaces. One specimen of each prepared group was selected for SEM group evaluation. The composite resin cylinders were bonded to the rest of the specimens for micro-shear bond strength measurement. The data were analyzed using two- way ANOVA and HSD -Turkey's tests. Application of the second layer had no significant effect on micro-shear bond strength to the enamel and dentin [p>0.05]. The dentinal micro- shear bond strength values of the specimens treated by Clearfil SE Bond, were significantly higher compared to Clearfil S3 Bond [p<0.05] but no significant effect was found on enamel bond strength [p>0.05]. Application of one layer of self- etch primer produced sufficient bond strength and there is no need to apply the second layer

[Effect of different surfactant solutions with and without EDTA on dentin surface free energy]

Increase in surface free energy of tooth activates enamel and dentin to enhance surface wettability and optimize adhesion. The purpose of this study was to evaluate the effect of different surfactant solutions with and without EDTA during preparation on dentin surface free energy. In this in vitro study, 88 selected molar teeth were cut in occlusal one-third of the crown and a flat dentin surface was obtained. Surfactant solutions with five different HLB [Hydrophil-Lipophil Balance] were selected and the flat dentin surfaces were abraded with a commercial high-speed cylindrical diamond bur while rinsing with the solutions. Two control groups were selected, including negative control [cutting with air-water spray], positive control [cutting with air-water spray and etching with phosphoric acid]. The study was carried on by depositing drops of two different liquids including distilled water [polar liquid] and methylene iodide [non-polar liquid] on the different treated surfaces and taking photographs of the drops by means of a digital camera. The contact angles were measured with AutoCad software. The surface free energy of dentin was then calculated using Fowkes equation. After selection of the most effective solution, a higher concentration was applied to determine the effect of concentration on surface free energy. After determining the effective concentration, the combined solution of surfactant and EDTA was evaluated. Data analysis was done by ANOVA and Duncan test with 95% signifieance level. The SEM study was done to evaluate smear layer formation in the specimens. The results revealed that use of surfactant on dentin surface decreased the surface energy while the surfactant with EDTA caused a significant increase in the surface energy compared to surfactant solution alone [Pvalue<0.05]. This increase in energy was equal to that of negative control. SEM study revealed that using surfactant with or without EDTA, removes the smear layer incompletely. 1] Surfactant solutions without EDTA decrease dentin surface energy at the same level of positive control group. 2] The result of measuring surface energy in negative control group and in the groups using this combined solution was identical with surface tension of water [72.8 j/m[2]]

[Evaluation and comparison of light conducting efficacy of cerana prefabricated inlay with inlays made by bioglass-ceramic and dental porcelain in increasing the hardness of posterior composites]

There are many techniques to overcome the light cured composite related problems including the depth, speed or rate and shrinkage patterns of polymerization. Among them, light transmitting and reflecting matrix, light conducting proximal wedges, incremental placement, use of glass-ceramic inserts and transparent cone, and application of different light exposure patterns could be referred. The goal of this study is evaluation and comparison of the light conducting ability and efficacy of prefabricated CERANA inlay with those made by dental porcelain and three new formulas of bioglass-ceramic and their effects in increasing the bottom hardness of posterior composite resin restorations. In this in vitro study, 90 molars were divided into nine groups of ten samples. Cavities similar to the medium size bur of CERANA kit were prepared in all samples. Forty inlays in the medium size and shape of CERANA with Vita 230 VMK dental porcelain and bioglass-ceramic with three new formulas with MOAZ4, MOAZ5, MOAZ6 codes were made. Four control groups including one bulk and incremental with two different light exposure distances ['0.0 mm to the tooth and 4.0 mm to the composite surface] were considered. All cavities in the control group were restored with A3 Colten composite and 80 seconds light exposure time for one-bulk negative control and testing groups and 2x40 seconds for incremental positive control groups with Coltolux 2.5. After epoxy resin embedding and diamond disk cutting, cooled with water and polishing with 1200 grit Sic paper, samples were tested with micro hardness tester from the top to the depth of four, one millimeter far from each other and 50 microns far from and along the inlays and also counterpart points in control groups. The data were tested with ANOVA and Duncan statistical tests. Along this study, dye penetration was done for all groups for statistical results confirmation. Statistical tests showed that tested groups with Vita 230 VMK, MOAZ6 and MOAZ4 inlays had 20%, 19% and 4% increase in a 4.0 mm depth. The group with CERANA inlays had 1% decrease in respect to the surface. The inlays made by MOAZ5 had the highest light conduction rate because they could cause a 41% increase at the deepest points [4.0mm depth]. In relation to control groups including [C-0] one bulk 0.0 mm, [C+0] incremental 0.0 mm, [C-4] one-bulk 4.0 mm, [C+4] incremental 4.0 mm, a 2%, 22%, 50% and 21% reduction in hardness at 4.0 mm depth in respect to the surface were noticed respectively. Finally, the dye penetration in control and testing groups could support the microhardness testing. Placement of inlays made by MOAZ5 in composite restorations causes a better light conduction and a higher hardness in deeper points of restoration and with monotone and simultaneous curing in different depths of restoration and a higher polymerization and hardness at the flour of restoration causing higher possibility for elimination or reduction of microleakage