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.

Aims: is to evaluate the castability of titanium alloy and compare it with that of nickel-chromium and cobalt-chromium alloys by measuring castability and porosity values. Materials and methods: A total of 30 samples were prepared for castability and porosity tests. Castability was measured by castability test according to Hinman method by measuring the numerical number of the reproduced segments of casting samples . Porosity value was measured by determined the porosity percentage according to (Archimedes) method . ANOVA and Duncun , s multiple range test were carried out to determine the significant difference at p ≤ 0.05% . Results: the results showed that titanium alloy has a lowest value of castability and the highest value of porosity percentage, While cobalt-chromium alloys has intermediate values. Nickel-chromium alloy has highest value of castability and the lowest value of porosity. Conclusion: there is a significant differences between the castabilty and porosity values among different casting alloys used. The differences between the catability values are related to variance between the melting temperature of the different casting alloys, the higher the melting temperature the less castability value.