During the drilling of oil wells, sometimes the digging drill passes through layers with coarse porosity which causes drilling mud loss. Concerning the preciousness of drilling mud, preventing its loss can be economically efficient and lead to a desirable drilling which increases productivity of the oil well. Due to the invaluable of the pores in different ground strata for Hydrocarbon material extraction purposes, a blocker should be used to prevent drilling mud loss. MAGNETITE CEMENT is used for this purpose.

Background: CEMENT space is necessary for seatabillity and fitness of cast crowns, but can affect crown's retention. In this study the interrelationship between them was investigated via die spacing.Materials and Method: For evaluating the effect of die spacing (CEMENT space) on crown retention after CEMENTation, 50 similar machined metallic dies were prepared and divided into five groups and coated with 0.2, 4, 6, 8 layers of paint-on standard die spacer, respectively. Cast crowns. Were fabricated on the dies using base metal alloys, and then CEMENTed with zinc phosphate CEMENT under a constant load of 5kg for 10 minutes. The samples were started in distilled water for 48 hours. Then the force required to remove each crown from the die was measured with instron.Results: Statistical analysis revealed a significant increase in the force required (crown retention) by adding layers of die spacer (p<0.05).Conclusion: Because retention didn't show any significant increase with more than 4 layers of die spacer, so optimum thickness of die spacer (or CEMENT space produced) is suggested to be 4 layers equal to 40 microns.

Introduction: Microleakage is one of the most important factors in the failure of root canal treatment. Microhardness is one of the physical properties of bioceramics that can be affected by various environmental factors such as enviromental humidity. The aim of this study was to evaluation the effect of adding water to semi-setting CEMENT on the microhardness and microleakage of CEM CEMENT. Methods: 50 single-rooted teeth were selected. Teeth were cut from the CEJ region and the apical 3 mm of the root were trimmed and dentinal blocks with 5 mm height were prepared Peeso reamer size 2 was used to prepare the canal. The teeth were divided into two groups of 23 cases and two groups of 2 positive and negative controls. In the first group, CEM-CEMENT prepared according to the manufacturer's instructions was placed in the canal. In the second group, after adding water to the semi-setting CEM CEMENT mixture, the canal was filled with this CEMENT. The samples were placed in 1% methylene blue for 3 days and then cut. Microleakage was recorded under a stereomicroscope. The microhardness of the samples was measured with Vickers device after mounting in acrylic resin. Statistical analysis was performed using SPSS19 software and Mann-Whitney Kruskal-Wallis and one-way ANOVA tests. Results: There was a statistically significant difference between the two groups in microleakage (P-Value <0. 008) and microhardness (P-Value <0. 001). Conclusion: According to the results of the present study, adding water to the semi-setting CEM CEMENT not only does have a very bad clinical effect, but also may even increase sealling ability.

In this paper CEMENT/carbon nanotube mechanical properties were predicted by micromechanical model. The effects of CNT properties such as internal, external diameters and its length as well as its volume percent on Young's modulus were investigated by this model. In addition, the effect of representative volume element (RVE) element shape (cylindrical, cubic and hexagonal) on Young's Modulus (E) was studied systematically. Finally, the predicted results were compared with CEMENT /CNT experimental results. The predicted results showed that by increasing external CNT diameters, CNT Volume percent and its length, Young's Modulus (E) was increased. However, the internal diameter of CNT didn't have significant effect on E. These data indicated that hexagonal element shape resulted higher E rather than square and cylindrical RVE shape. Comparison of predicated E and experimental E showed that the proposed model could predict young modules with high accuracy. These results showed that micro mechanical modeling is a valuable method for predication of CEMENT/CNT mechanical properties in nanoscale.