elastomeric materials: silicones (polyvinyl siloxane): condensation-cured silicones, addition silicones, vinyl polyether silicones (VPES) polyethers ; polysulphides; rigid materials: plaster of Paris; impression compound; zinc oxide and eugenol-based impression paste; Techniques for taking impression. Perhaps the greatest challenge clinicians face while capturing an impression is achieving complete reproduction of the prepared finish line, particularly with sub- or equigingival margins. These are high precision and essential for impressions that will be used for the fabrica-tion of indirect restorations and laboratory fabricated aligners. Addition Silicones – Addition silicones are the most popular type of elastomeric impression mat erial, especially for crown and bridge impressions. Author: R Gibbons, RDN, PTTLS Supplied as. they often require special equipment to prepare. Available as 1- Light body. The purpose of this in vitro study was to compare the trueness and precision of digital dental casts obtained from the direct digitization of 2 … -disadvantages = complex prep. Therefore, the alginate impression materials may have the same degrees of accuracy as those of elastomeric impression materials but, in reality, alginate impression materials still perform more poorly than rubber base impression materials. Non-aqueous elastomeric impression materials include polysulfide, polyether, condensation silicone, and addition silicone (vinyl polysiloxane). Elastomeric impression materials offer high elastic recovery and acceptable flexibility on removal of the impression from the mouth . – They are the most accurate, stable, and expensive impression materials. Materials and methods: The values of the first three variables were computed from a tensile load test of 10 dumbbell-shaped specimens of each impression material. Also known as conventional silicones. Elastomeric. – Hydrocolloid impression materials are quite hydrophilic, but the same cannot be said for all impression materials. brittle → ZOE is ___ in texture when dried or set. elastomeric impression materials must be able to reproduce fine detail of 25 μm or less. An electronic search of the Scopus and PubMed databases was performed in November 2010. 3- Heavy body. The trueness and precision of the digitization of these new elastomeric impression materials are unclear. As the residual ridges resorb, the tissues become unsupported and displaceable; the use of conventional impression techniques will result in a distorted impression. It is found that to record fine detail viscosity should be lower. # Disadvantage of polysulfide as an impression material : A. (b) Disadvantages – The disadvantage … Conclusion: Overall contemporary retraction materials showed low potential for polymerization inhibition of elastomeric impression materials. Purpose: This study investigates the modulus of elasticity, yield strength, the strain at yield point, and the tear energy of nine elastomeric impression materials. Recently, new elastomeric impression materials have been introduced, with the claim of very high elastic recovery and high tear and tensile strengths. Nonaqueous elastomeric → Materials that set hard or rigid are known as what types of impression material? Composition: Base paste. Disadvantages of reversible Hydrocolloid-A lot of equipment -Inaccurate and distorted impression when the tray is removed from the mouth too soon, improper removal or inadequate amount of material in tray.-Grainy material caused by insufficient boiling or keeping the storage temperature too low. Base paste (white) Accelerator (brown/grey) Available in 3 viscosities: Light bodied; Medium bodied; Heavy bodied; Composition: Base paste: – They are clean and do not have an unpleasant taste or smell. The operating principle involves the application of a fixed compressive strain and the resulting stress is measured. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Mechanical properties of elastomeric impression materials (H LU, B NGUYEN - 2004 ) Mechanical properties of three commercial elastomeric impression materials two addition silicone impression materials and one polyether material with low and high viscosities were compared. Wilson, H. J.; Elastomeric impression materials. High cost B. materials leaching out C. Stretching leads to distortion D. Difficulty in cast pouring # Hydrocolloid material shows all except : A. Hysteresis B. Imbibition C. Recrystallization D. Syneresis # Impression material which has a high incidence of air porosity is : A. Alginate impression material B. Research Article Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison DinoRe, 1 FrancescoDeAngelis, 2 GabrieleAugusti, 1 DavideAugusti, 1 SergioCaputi, 2 MaurizioD Amario, 3 andCamilloD Arcangelo 2 Department of Oral Rehabilitation, Istituto Stomatologico Italiano, University of Milan, Milan, Italy non aqueous elastomeric impression materials. A nonionic surfactant can be added to the paste in the manufacturing process to render a degree of hydrophilicity to the surface of the material. – Addition silicone impression materials are a lso called vinyl polysiloxanes and ELASTOMERIC IMPRESSION MATERIALS The impression materials discussed so far are not good enough generally for taking accurate impressions of the dental patient. Purpose. The differences between impression materials, as outlined above, are the materials themselves and the purpose they are used for. The aim of the present paper was to review the literature concerning the dimensional stability of dental elastomeric impression materials, to support recommendations to control the variables that influence the accuracy of these materials. In 1989, Peutzfeldt and Amusen studied the accuracies of alginate and elastometric impression materials. True False . CONDENSATION SILICONES. Indicates having elastic or rubber like qualities. 13. – In dentistry, we take impressions of teeth and their supporting structur es. These supporting structures include gingiva, a lveolar bone or residual ridge, hard and soft palate, and frenums, which are muscle attachments. • Putty consistency is supplied in jar. PVS impression materials can make details of even 1 to 2μm. Polyvinyl siloxane and polyether impression materials remain dimensionally accurate … But for elastomeric impression materials these methods have proven to be ineffective as they do not prevent cross contamination among the dental team. Popularity of Reversible Hydrocolloid ( Agar ) – With the various advantages and disadvantages of reversible hydrocolloid material, one would expect dentistry to have a love–hate relationship with this material. Reprint requests to: DR. J. F. MCCABE UNIVERSITY OF NEWCASTLE UPON TYNE THE DENTAL SCHOOL FRAMLINGTON PLACE NEWCASTLE L'PON TYNE NE2 4BW ENGLAND 104 JANUARY 1985 VOtUME … Impression Materials A. True False . It is also known as Mercaptan or Thiokol. • Regardless of type all elastomeric impression materials are supplied as two paste system (base and catalyst) in collapsible tubes. – Again, the gypsum product, when mixed with water, easily wets the surface of the impression material, which is predominantly water. Current-generation elastomeric impression materials and digital scanners are capable of quickly and accurately capturing prepared teeth. McCabe, J. F., and Bowman, A. J.: The rheological properties of dental impression materials. One of the disadvantages of the silicone impression materials (including condensation silicones) is their inherent hydrophobic nature. It was the first type of silicone impression material. This paper describes the development of an instrument for determining consistency, working time and setting time of elastomeric impression materials. Elastomeric impression materials have been marketed for optimizing direct digital acquisition without requiring a stone cast. Setting occurs in room temp , so called as RTV silicones. silicone → This is the most popular type of elastomeric impression material. This instrument has been called a Comprheometer. Br Dent J 151:179, 1981. – Few dentists use reversible hydrocolloid, but those who do, love it. Types of elastomeric impression materials Composition Setting reaction Advantages and disadvantages #NEETMDS #dentistry #dentalmaterials Start studying impression materials elastomers. General Comments – Impression materials are used to make replicas (models or casts) of t eeth and other oral tissues. elastomeric impression materials on repeated pours would suggest that addition silicones and polyethers to a certain extent were least affected with delay in pouring the impression. er efore, the impression technique needs to be modi ed. Each of the materials has advantages and disadvantages, but they are each used for a different purpose and are effective and commonly used products in dentistry today. 5. 2- Medium body. • Disadvantages – Does not reproduce fine detail as reliably as other elastomeric impression materials – Dimensional stability is poor – Must be poured immediately to prevent distortion Packaging • Powder packaged in bulk – Sealed screw top plastic container or hermetically sealed metal can . True False . With elastomeric impression materials such as polyvinyl siloxane, polyether, and polysulfide, the dimensional accuracy is usually time dependent, with greater dimensional accuracy occurring immediately after polymerization is complete but declining as the impression is stored for extended periods of time . Viscosity is also an important property of a material for the precise impression in a cast. pouring the impression with gypsum products is easier than with elastomeric impression materials. (ZOE) or elastomeric impression materials because of the inherent accuracy of these materials and their propensity to distribute pressure equally [ ]. What are the disadvantages of elastomeric impression materials?-strong sulfuric odor and bad taste -staining of clothes -setting time is ten min-water,saliva and blood affect setting time -glove powder can contaminate impression. Br Dent J 121:277, 1966. PolysulFide This was first elastomeric impression material to be introduced. 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