Aims:To evaluate the effect of thickness of acrylic denture base resin on the transverse strength, also to evaluate the effect of metal and fiber reinforcements on the fracture resistance of denture base resin by four mechanical tests: Transverse strength; Charpy impact strength; Tensile strength and Rockwell Indentation Hardness. Materials and methods : Heat-cured resin, and three types of reinforcing metals were used which were: The cobalt-chromium alloy mesh, stainless steel wire and nickel alloy plate. Three forms of glass fiber also were used: Random, woven, and aligned unidirectional. The effect of these reinforcing materials on the mechanical properties of heat-cured resin had been evaluated by measuring the transverse strength by the Instron testing machine, tensile strength by the Textile tensile strength Tester, the impact strength by the Charpy type impact Tester and finally the hardness by the Rockwell hardness tester. Three hundred samples were prepared in this study. Results: Revealed a statistically significant effect of thickness on the transverse strength of heat-cured resin. Results also showed that all forms of fiber and metal reinforcements had a significant effect on the transverse strength, tensile strength , impact strength and hardness of denture base resin. Conclusions: The thickness significantly increased the transverse strength of denture base resin. All forms of metal and glass fiber reinforcement significantly improved the transverse strength, impact strength and tensile strength of denture base resin. All forms of metal and fiber reinforcement acted to reduce the hardness of denture base resin.

The aim of this study was to evaluate the effect of three types of natural medicinal plants oils on the transverse strength, residual monomer and hardness of polymethylmethacrylate. Materials and methods: Total number of samples of (105) have been prepared in this study. Fifteen samples of heat cured ProBase acrylic resin were prepared without additives (Control), and (90) samples were prepared with additives (Ginger oil ,Meramia and Eucalyptus oil) in two concentrations (1.5 and 2.5) to evaluate transverse strength, indentation hardness and residual monomer. Results: The results showed a significant difference between control and addition groups in the transverse strength and hardness tests. The addition of oils decreased the transverse strength ,and increased the hardness.There was no significant difference between the residual monomer for control and addition groups, but the control group at the first day showed higher residual monomer release. Conclusion: The addition of eucalyptus , meramia and ginger oils to acrylic resin decreased the transverse strength , increased its hardness and showed no significant difference in residual monomer.

Aims: To evaluate and compare the effect of human saliva, artificial saliva and propolis extract on the wettability of heat−cured and visible light −cured denture base material .Materials and Methods: A total of 80 samples were prepared , 40 samples prepared from heat cured resin and the other 40 samples were prepared from light cured resin. These two groups were divided into four subgroups, control group, human saliva, artificial saliva and propolis. Contact angle measurements by sessile drop method with a micropipette using digital camera to determine the wettability of these samples. Mean values were compared statistically with one way analysis of variance (ANOVA),Duncan's multiple range test and t−test to determine the significant difference among the tested groups. Results: There is a significant differences of the mean values of the contact angle among the tested groups. The contact angle significantly decreased in all the treated samples. Conclusion: Heat cured resin has more wettability than light cured resin. Human saliva, artificial saliva and propolis increased the wettability of both heat cured and light cured resin.

Aims: The aim of this study was to evaluate the effect of mixing different concentrations of chlorhexidine, iodine ,and sodium hypochlorite solutions on the setting time and dimensional change of alginate impression material. Materials and methods: Total number of samples (40) has been prepared in this study. Ten samples for control group made from pouring alginate impressions of metal model .The other groups made by mixing alginate with 0.05% iodine, 0.5% chlorhexidine and 0.5% sodium hypochlorite solutions. Dimensional change was measured with AutoCAD program .The Setting time was also measured for each group. Statistical analysis was performed using ANOVA and Duncan multiple range test. Results: no significant difference in the linear dimensional change among the tested groups ,sodium hypochlorite added to alginate as disinfectant showed the highest dimensional changes among the other groups. There was a significant difference among the tested groups in the setting time. It was found that treating the alginate with sodium hypochlorite and chlorhexidine disinfecting agents accelerated the setting time of the material. Conclusion: The testing disinfecting agents can be used safely regarding dimensional change.

Aims:To evaluate and compare the number and surface area of surface porosities of different dental investment materials by using two mixing techniques. Materials and Methods: Two mixing techniques; manual and mechanical were used to prepare specimens for four dental investment materials: Biosint Supra, Rema Exakt, Rematitan Plus, and Deguvest soft. Computer programs are used to measure the number and surface area of the porosities to compare among them. ANOVA, Duncan multiple range test in addition to T-test were carried out to determine the significant difference at P<0.05. Results: In relation to the surface area of the porosities, there are high significant differences among the investment materials tested, and high significant difference is presented between the two mixing techniques tested with the manual mixing technique and showing higher value than the mechanical vacuum mixing technique. In relation to the number of porosities, there are no significant difference among the investment materials tested, but there are very high significant differences between the two mixing techniques tested with the manual mixing technique and showing higher value than the mechanical vacuum mixing technique. Conclusions: the number and surface area of the surface porosities differ from the different materials used, and differ in the same material by changing the mixing technique.