Review of Dental Impression Materials

Abstract

M ajor advances in impression materials and their application have occurred during the last decade, with greater emphasis being placed on rubber impression materials than on dental compound, zinc oxide-eugenol, and agar and alginate. Of particular interest has been the effect of disinfection solutions on the qualities of impressions and the biocompatibility of impression materials. The principal advance in hydrocolloids has been the introduction of the agar/alginate impression technique, which has simplified the procedure and improved the quality of gypsum dies compared with those prepared in alginate impressions. The tear strength of some alginates has been improved, and some have been formulated so that the powder is dustless, thus reducing the health hazard as a result of patient inhalation of dust during the dispensing process. Polyether and silicone impression materials have been modified so that the working time, viscosity, and flexibility of the polyethers have been improved and, with the introduction of addition silicones, their accuracy has become exceptional. Although the early addition silicones liberated hydrogen after setting, thus delaying the pouring of models and dies, most addition silicones have been improved so that no hydrogen is released and dies can be poured immediately. The introduction of automatic mixing systems for addition silicones has simplified their manipulation, has reduced the number of voids in impressions, and has reduced the amount of material wasted. The incorporation of surfactants into addition silicones has made them hydrophilic, with wetting properties similar to those of polyethers, and has made pouring bubble-free gypsum dies easier. This review is confined to published and unpublished information of the past decade. It will also suggest trends that should be anticipated in the near future based on this information. The review will not present information developed before 1975, which is available in several textbooks on dental materials by Craig (1985a), Phillips (1982), and Williams and Cunningham (1979). RIGID IMPRESSION MATERIALS IMPRESSION COMPOUND The use of dental tray compound has decreased with the increased substitution of acrylic tray materials. The application of dental impression compound has also decreased with the increased use of rubber impression materials, which can also be electroformed to produce metal dies. However, impression compound is useful for checking cavity preparations for undercuts and for making impressions of full crown preparations where gingival tissues must be displaced. Excessive temperature rise of the pulp chamber is undesirable, and Grajower et al. (1975) recently measured temperature increases in the pulp when

Effects of the space for wash materials on sulcus depth reproduction with addition-curing silicone using two-step putty-wash technique

“…Since additioncuring silicone rubber impression materials (polyvinyl siloxane, PVS) demonstrate low curing shrinkage and high dimensional stability, they are frequently used for impressions requiring high accuracy [1][2][3] . Several impression techniques have been suggested.…”

Dimensional stability of polyvinyl siloxane impression material reproducing the sulcular area

“…The dimensional stability of elastomeric impression materials is influenced by shrinkage caused by polymerization, the byproducts of chemical reactions, thermal changes and incomplete elastic recovery from deformation 6,7,9) , while factors such as impression disinfection 24,25) , pouring time 26,27) and the impression technique 6,11,12,15) affect the accuracy. The present work is one of the few studies to directly assess the accuracy and dimensional stability of a thin impression margin (1×0.2 mm) over time using a reproduction of the finish line and emergence profile on the impression material itself.…”

“…FPDs with clinically unacceptable marginal gaps retain significantly more plaque and cause higher rates of gingivitis, periodontal pockets 2,3) and secondary caries 4) compared to adequately restored teeth. The polyvinyl siloxane (PVS) (also termed addition silicone) impression materials have become extremely popular because of the combination of their excellent physical properties, good handling characteristics and almost ideal dimensional stability [5][6][7][8] . Among the excellent physical properties of these materials are their high accuracy for recording fine details and the best elastic recovery of all of the available impression materials 9) .…”

Functional relationship of room temperature and setting time of alginate impression material

“…1,3 The temperature dependence of the alginate reaction process was of the Arrhenius type. 5,15 The Arrhenius law is the dependency of chemical reaction rate on the temperature. 16 The chemical reaction rate speed up with increasing temperature.…”

“…3 This reaction is a temperaturedependence reaction. 5 To fulfill the critical requirements of a dental impression material, the reaction must be controlled to attain the desirable properties of consistency, working time, setting time, strength, elastic quality, and smooth hard surface on gypsum cast. These requirements are achieved by adding agents to control the rate of reaction, develop strength and elasticity in the gel, and counteract the delaying effect of alginate on the setting of gypsum products.…”