Abstract

Background: Gypsum die materials are widely used in dental practice for the fabrication of hard dies. An ideal die material should have superior abrasion resistance and high strength. However, the strength and abrasion resistance of gypsum die material is not satisfactory. Accidental wear of the gypsum die occurs during carving of the wax pattern or fracture, especially the teeth. In places where hard water is common, it is necessary to use distilled water or double distilled water for obtaining the optimum properties of die stones. Manufacturer recommended values of water-powder (W/P) ratios should be used to get optimum properties for gypsum die materials.

Objectives: To evaluate the effect of different sources of water on the properties of Type IV die stones. Changes in the properties of die stones when mixed with water from eight different sources were studied and evaluated.

Materials and Methods: Two commercially available type IV die stone materials were used. These materials were mixed with eight different types of water samples with varying hardness values. The properties tested are setting times, compressive strength, hardness and analyzed the ingredients of water used. Effect of water powder ratio on the properties also studied.

Results: Double distilled or distilled water is most suitable to manipulate gypsum die material and obtain highest strength and hardness. Hardness of water decreased the strength and hardness of gypsum die significantly. As the higher W/P ratio used to manipulate, the setting times increased and strength and hardness decreased significantly.

Conclusion: In the present study, die stones mixed with double distilled water and distilled water produced strong and hard die compared to die stones mixed with hard water. In many places hard water is available commonly. In those places, it is necessary to use double distilled or distilled water for obtaining the optimum properties of die stones. Increase in W/P ratio significantly decreases the mechanical properties of die stone. Hence manufacturer’s recommendation should be followed to get optimum properties of die stone.

Key words: Die materials, Water hardness, Surface hardness, Strength, Setting times