الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 124 |  |  |
| | | from | 124 | | |
Abstract
Introduction : Research work that have been conducted to evaluate the effect of new dentin bonding approaches, consisting of DMSO/H2O pretreatments applied to extensively air-dried dentin have been scarce so far. Until now, there is lack of data regarding the immediate and long-term effect on bond strength and nanoleakage of two-step etch-and-rinse adhesives and universal adhesives. >The Aim of this study: To evaluate and compare the microtensile bond strength of etch-and-rinse adhesives after surface pretreatment with Dimethyl-Sulfoxide primer. In time, it evaluate the nanoleakage pattern at resin/dentin interface. Materials and methods:fifty-six sound human molars were assigned into two groups of 28 teeth each. After disinfection, they were fixed in self-cure acrylic resin. Flat dentin surfaces were exposed using diamond saw. A standardized smear layer was formed by 600-grit silicon carbide paper under running water. Etch-and-rinse adhesives applied to the first group and universal adhesives (etch-and rinse mode) to the second group. Each group further divided into 2 sub-groups according to the surface pretreatment method of 14 teeth each. Sub- group A: without application of DMSO primer, sub-group B: with application of DMSO primer. Resin composite block (tetric N-ceram) was built up incrementally (each increment two mm thickness). Each sub-group will be divided into 2 divisions according to the testing time; (n=7): division A: specimen will be tested immediately after 24 hours water storage in distilled water, while in division B (n=7): were tested after aging in artificial saliva at 37±1 °C using an incubator for 6 months. All specimens were subjected to µTBS test using universal testing machine. The failure mode was analyzed using Stereomicroscope. An addition, eight molars were randomly allocated and bonding was performed following as of microtensile bond strength. They were used for nanoleakage expression by SEM. The collected µTBS data was statistically analyzed for variables by three-way analysis of variance (ANOVA) and Tukey post-hoc multiple comparison tests. Level of significance was set at (p<0.05). Results: The results of Three-way ANOVA test revealed that “type of the adhesive” ,“surface pretreatment “ and “storage time” significantly affect microtensile bond strength mean values (p˂0.05).Regarding un-stored groups, there were etch-and-rinse adhesives without DMSO pretreatment teeth exhibit lowest bond strength value in comparison with all groups. Significant difference was found between etch-and-rinse adhesive with DMSO pretreatment and etch-and-rinse adhesive without DMSO pretreatment. In groups tested after 6-months storage, etch-and rinse adhesives and universal adhesives without DMSO pretreatment exhibited the lowest bond strength value. A significant difference was found between etch-and-rinse adhesive with DMSO pretreatment and etch-and-rinse adhesive without DMSO pretreatment. No significant difference was found between universal adhesives with/without DMSO pretreatment in both periods. All tested specimens presented traces of silver impregnation in the hybrid layer with highest silver deposition in etch-and-rinse adhesive control group. Conclusion: Dimethyl-sulfoxide dry-bonding technique improves bond performance of etch-and-rinse adhesives after long-term aging. The introduced new concept of bonding produced significantly higher dentin bond strengths over time in comparison to the control group, but it did not prevent bond strength loss. In addition, hybrid layers with higher hydrolytic stability, presenting reduced levels of nanoleakage after long-term aging.