Aims:To evaluate the effect of the microwave disinfection on the dimensional changes of the heatcured acrylic resin. Materials and Methods: Heat-cured acrylic resin was used in this study. Thirty two disk-shaped specimens with reference points were prepared to evaluate the linear dimensional changes of the heat-cured acrylic resin that sterilized by microwave irradiation and by chemical solutions chlorhexidine and sodium hypochlorite. The specimens were divided into four tested groups, eight specimens for each group. Group I as control group and other groups divided according to the sterilization method. The dimensional change was evaluated with an Electronic Digital Caliper. Mean values wear compared statistically with: One-way Analysis of Variance (ANOVA), followed by Duncan ' s Multiple Range Test to determine the significant different among the tested groups at (p≤0.05) level of significance. Results: They showed that there was a highly significant difference of the means values of the linear dimensional change among the four tested groups. Specimens sterilized by microwave irradiation have a higher value than that sterilized by the chemical solutions. Conclusions:The results of this study appeared that sterilization by the microwave irradiation produce a significant effect on the dimensional stability of the heat-cured acrylic resin, while sterilization by chemical solution produce no significant difference.

Aims: To evaluate the effect of the different curing methods conventional water bath heat-curing and microwave energy curing method and different immersion periods on the water sorption and solubility of the different types of heat-cured acrylic resins. Materials and methods: Water sorption and solubility were measured by means of mass change in the materials after water saturation and dehydration. Two different commercial heat-cured acrylic resins Major Base 2, and Quayle Dental resins were used in this study. Specimens were divided into two groups depending on the curing method. Thirty two specimens were prepared, eight specimens for each material in each group. Specimens were immersed in distilled water, and then subsequently removed from their containers at 1 week and 1 month of immersion for evaluation. Mean values wear compared statistically with one way analysis of variance followed by Duncan's multiple range test to determined the significant different among the groups at (p< 0.05) level of significance. Results: showed that the curing method and immersion period have a significant effect on the water sorption and solubility ratios of the resins. Curing by microwave energy method and increasing immersion period caused increasing in the ratios. The type of heat-cured acrylic resin has an effect but the difference was not significant. Conclusion: the curing method, immersion period and types of the acrylic resin have an effect on the absorption and solubility ratios.

Aims: This study aims to evaluate the effect of the thermopress curing technique on the water sorption and solubility of the cold-cured and heat-cured acrylic resins and compared this technique with the bench curing technique used for the cold-cured resin and with the conventional water bath curing technique for the heat-cured resin. Materials and Methods: they were to measure the water sorption and solubility, the specimens were prepared as disks with a dimension according to the ADA Specification No. 12. So specimens were divided into five groups depending on the type of the resin ( cold and heatcured ) methods of curing which were ( thermopress, conventional water bath and bench cure ) and the time of curing cycle. Specimens were weighed before and after immersion in the distilled water and after drying with silica gel using an electronic balance to measure the water sorption and solubility. One way analysis of variance (ANOVA) followed by Duncan , s multiple range test was performed to determined the significant different between the mean values among the tested groups at (p< 0.05) level of significance. Results: There is a significant differences between the water sorption and solubility of resin that cured by the different curing methods and different curing cycle times. The water sorption and solubility of resin specimens that cured by thermopress have the higher values. Conclusions: The water sorption and solubility of the cold and heat-cured acrylic resins is affected by the curing method. The curing under higher pressure produces specimens with lower water sorption and solubility values.

Aim: Using scanner image to digitally analyze the brightness and the effect of the type the of material, thickness and immersion of material in different solutions on the color change of the heat-cured acrylic resin denture base material. Materials and Methods: Two types of heat-cured acrylic resin denture base material were used. Totally 30 samples were prepared for uniform dimension for each color test. Sample scanner imaged and color metric is analyzed with software program Adob Photoshop 9.0. The CommissionInte´rnationale de l'E´ clairage for characterizing color (CIE L*a*b*) color difference metrics were used for the performance analysis. Color change (ΔE) value calculated to determine clinically acceptable color change. Statistically ANOVA, Student's t-test , Dunnett pairwise multiple comparison t-test and Duncan's multiple range test were carried out to determine the significant differences at p≤ 0.05. Results: The results appeared that there is a significant differences of the brightness value before and after polishing of the acrylic resin samples. And statistically there is a significant effect of type, thickness, and immersion in different solution on the color change of the tested materials which is clinically not acceptable. Conclusion : The result appeared that scanner gives an accurate image to digitally evaluate brightness and color change of dental materials with CIE L*a*b*color system.

Aim:The aim of this study was to prepare die stone material by dehydration of the local natural raw gypsum in boiling with 30% calcium chloride solution , and then evaluated some physical properties of this prepared die stone. Materials and methods : The values of some physical properties of the prepared die stone in boiling with 30% calcium chloride solution which are water/powder ratio, setting time, and compressive strength were compared with that of three types of gypsum products commercial die stone, Elite type III dental stone and Iraqi plaster. The data were collected , mean and standard deviation were determined. Statistically, (ANOVA) and Dunnett Pairwise Multiple Comparison test were carried out to determine the significant differences at p≤ 0.05 Results: Results showed that there were no significant differences between the locally prepared die stone and the commercial one at p≤ 0.05 in water/powder ratio and setting time values, but it was significant difference in compressive strength. But there are a significant difference between the physical properties of the locally prepared die stone and Elite type III dental stone and Iraqi plaster. Conclusions: The results showed the physical properties of the locally prepared die stone approach the physical properties of the commercial product according to the recommendation of ADA for gypsum products.