![]() ![]() Models, casts, and dies always are made from an impression of the soft and hard oral tissues. Dies are highly accurate replicas of a single tooth and generally are used to make metal crowns or inlays. Casts of teeth are used to make orthodontic retainers, and casts of the remaining ridges in the edentulous patient are used to make dentures. For example, orthodontists use study models to evaluate the crowding of the teeth or progress in correction of that crowding. Study models are used to observe the patient’s oral structures. Each of these replicas has a specific purpose in dental practice. These replicas are called study models, casts, or dies. In dentistry, replicas of the hard and soft tissues are used for diagnosis and treatment of oral disease. Describe the general manipulation properties of epoxy model materials. Describe the general setting reaction of epoxy model materials.ġ6. Give a specific method for disinfecting gypsum models, and state whether it is better to disinfect an impression or a model.ġ5. Describe the various methods of spatulation of gypsum materials.ġ4. Describe the general procedure for measuring, mixing, and pouring an impression with a gypsum material.ġ3. Define the properties strength, hardness, abrasion resistance, and dimensional accuracy, and explain why they are important clinically to gypsum materials.ġ2. Explain the concept of wetting and why it is important to gypsum materials.ġ1. Describe the factors that influence the ability of gypsum to reproduce detail in an impression.ġ0. Describe the differences between initial and final setting times, their chemical relevance, and explain how each can be determined.ĩ. Define water–powder ratio, its values for the various types of gypsum, and its effect on the physical properties of gypsum materials.Ĩ. Name accelerators and retarders that affect the gypsum setting reaction.ħ. Describe the setting reaction of gypsum materials and the effect of excess water on the set mass.Ħ. Describe the physical and chemical difference between model plaster, dental stone, and high-strength dental stone.ĥ. Compare the advantages and disadvantages of the different model and die materials in terms of abrasion resistance, ease of use, time and equipment required, and other relevant properties.Ĥ. Describe the physical properties important to model and die materials, and explain why they are important.ģ. Define the terms study model, cast, and die as they relate to model and die materials.Ģ. All findings point to the superiority of the addition silicone compared to the condensation silicone.ĭimensional stability fixed partial dentures impression technique review silicone impression material.1. The literature review confirmed the lack of standardization of methodologies applied in the research and their great diversity. In the reviewed literature several factors that influence the dimensional stability and accuracy of silicone impression molds, including the choice of the type of viscosity, impression material thickness, impression technique, retention of the impression material on the tray, storage time before the casting, number of castings, hydrophilicity of the material, release of byproducts, contraction after polymerization, thermal contraction and incomplete elastic recovery were presented. Scientific papers and studies were selected according to the materials used, the sample size, impression technique, storage time, type of measurements and use of spacer for the period between 20. The purpose of this paper is to provide a literature review of relevant scientific papers which discuss the use of various silicone impression materials, different impression techniques and to evaluate their impact on the dimensional stability and accuracy of the obtained impressions. A quality-made dental impression is a prerequisite for successful fixed-prosthodontic fabrication and is directly dependent on the dimensional stability, accuracy and flexibility of the elastomeric impression materials, as well as on the appropriately used impression techniques. ![]()
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