PURPOSE: To evaluate the effect of ZrO 2 nanoparticles incorporation (in two different ratios 1% and 3%) on some properties of one high-impact heat cured PMMA resin material when it was processed by two different methods (Conventional and Microwave curing methods). Materials & Methods: One high-impact heat cured PMMA resin (Trevalon Hi) was used in this study to be modified with nano-ZrO 2 in two different ratios (1% and 3%). Both unmodified and modified high-impact heat cured PMMA resin were subjected to three different tests (Flexural strength test, Microhardness test, and Color stability test). A total of ninety specimens were prepared, thirty specimens for each test (N=30). Within each test specimens, there were three groups (n=10), (HI) group: was prepared from high-impact heat cured PMMA resin without modification by nano-ZrO 2 (as a control group). (1%n-ZrO 2 HI) group: was prepared from high-impact heat cured PMMA resin modified by 1% nano-ZrO 2. (3%n-ZrO 2 HI) group: was prepared from high-impact heat cured PMMA resin modified by 3% nano-ZrO 2 .Within each group, five specimens were prepared by conventional water-bath curing method, while the other five specimens were prepared by microwave curing. The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM® SPSS® Statistics Version 20 for Windows. Results: Modification of high-impact heat cured PMMA resin with (1% and 3%) nano-ZrO 2 resulted in significant increasing in the mean values of flexural strength and VHN of all tested groups (p<0.05), while the effect on the color stability of the resin was slight. Conclusion: Within the limitation of this study, modification of high-impact heat cured PMMA resin with zirconia nanoparticles up to 3% could improve the flexural strength and surface microhardness with slight effect on the color. Microwave curing of high-impact heat cured PMMA resin gives better results than conventional one.

PURPOSE:To evaluate the bioactive resin modified GIC material (Activa) vs. conventional one (Vitremer) clinically and laboratory. Materials & Methods: Clinically:Fifteen healthy children of both sexes aged (4-7) having a bilateral similar initial occlusal caries on the lower 2 nd primary molars were selected. A split-mouth design was used where conventional Class I cavities were prepared on carious molars. One side was restored with Activa and the contra-lateral side restored with Vitremer (control). The patients were recalled for clinical evaluation at 3, 6 and 12 months postoperative. The modified United States Public Health Service (USPHS) evaluation criteria were used. Laboratory: included: 1. Mechanical strength tests (compressive and diametral tensile). 2. Shear bond strength test between both restorative materials and dentin. Statistical analysis: Mann Whitney test was used for clinical evaluation, while t-test and ANOVA were used for laboratory evaluation. The significance level was set at P ≤ 0.05. Results: Clinically:The overall clinical outcome showed no significant difference between both groups in all evaluated criteria (p>0.05). Laboratory: Activa showed higher values than Vitremer in all tested groups and the differences were significant (p<0.05) Conclusion: Activa recorded better scores than Vitremer in nearly all tested clinical criteria but without significant differences between them during recall-time intervals. But, the laboratory differences in all tested groups were significant.

No abstract

Objective: The objective of this study was to evaluate, in vitro, the influence of two concentrations of carbamide peroxide bleaching agents with and without topical desensitizing gels on enamel microhardness, roughness, and shear bond strength to orthodontic metal brackets. Methods: One hundred and sixty-eight (168) human extracted premolars for orthodontic purpose were obtained and randomly divided into seven groups (n =24): Group 1, control group (Neither bleaching nor desensitizing); Group 2, bleached with 22% carbamide peroxide; Group 3, bleached with 22% carbamide peroxide followed by Minerals desensitizing gel; Group 4, bleached with 22% carbamide peroxide followed by ''D.M. Sense'' desensitizing gel; Group 5, bleached with 35% carbamide peroxide; Group 6, bleached with 35% carbamide peroxide followed by Minerals desensitizing gel; Group 7, bleached with 35% carbamide peroxide followed by ''D.M. Sense'' desensitizing gel. Microhardness test and roughness measurements were carried on specimens immediately after finishing of treatment, using Vickers Diamond Microhardness Tester and Roughness Analyzer respectively. Only specimens for brackets shear bond strength (SBS) were stored for 7 days in distilled water after treatments and before testing. Shear bond strength were tested using Instron Universal Testing Machine Results: Statistical significant differences were found between groups. Groups that received bleaching treatments only, showed greater deterioration in all tested properties than, groups received desensitizing treatments after bleaching treatment. Conclusion: Application of desensitizing agent after in-home bleaching is highly recommended to minimize deleterious effects of bleaching agents.

An in-vitro experimental study was conducted to compare retention and deformity of three different RPD clasp materials (poly ether ether ketone, nickle titanium alloy, and acetal materials) with conventional cobalt chromium alloy; material and methods; A total of (56) RPD's Aker clasps were divided into four equal main groups (n=14) according to type of clasp materials; poly ether ether ketone (PEEK), nickle titanium (Ni/Ti), acetal, and cobalt chromium (Co/Cr) materials. All clasp samples in each group were used for retention test and deformity test.Results: One way ANOVA test and Pairwise comparison between each 2 groups using Post Hoc Test were used for retention and deformity tests at base line and after 730 , 1460 ,2190 and 2920 cycles revealed that metallic (Co/Cr) clasps ofer greater retentive forces followed by(Ni/ Ti) than non metallic (PEEK) then acetal resin clasps with differences considered as Statistically significant as p ≤ 0.05 at all testing loading cycles. also (Co/Cr) clasps offer greater deformity value followed by(Ni/Ti) than non metallic (PEEK) and acetal resin clasps with differences considered as Statistically significant as p ≤ 0.05 nearly at all testing loading cycles except at 2920 cycles where non-metallic (PEEK) followed by acetal resin clasps offer greater deformity than metallic(Co/Cr) clasps then(Ni/Ti) with differences considered as Statistically significant as p ≤ 0.05.Conclusion within limitations of this study it is better to use PEEK clasps for esthetic reasons; and (Co/Cr) clasps for retention reasons.