This procedure results in what is essentially an intraoral custom-made tray formed by the putty. Syneresis—The expression of fluid onto the surface of gel structures. In this chapter, they are called elastomeric impression materials. The purpose of this article is to review and understand currently used elastomeric impression materials in the fabrication of complete dentures. When the material is used correctly, either custom or stock trays yield clinically acceptable impressions. What are the steps needed to produce casts and dies for prosthetic procedures? mixing tip will have a 2048- or 4096-striation structure, which can be treated as a uniformly mixed stream of material. Space for the light-body “wash” material is provided either by cutting away some of the “tray” putty or by using a thin polyethylene sheet as a spacer between the putty and the prepared teeth during preliminary impression making. Pouring of a stone cast in a polyether or polysulfide impression does not require the aid of a surfactant. Copyright © 1981 Published by Mosby, Inc. https://doi.org/10.1016/0022-3913(81)90018-4. The thick putty material is placed in a stock tray and a preliminary impression is made. There are two types of polyether impression materials. One should be aware that this is not economical, as a portion of the paste is not used. However, this hydrophobicity makes pouring with gypsum products challenging, as it increases the potential of forming voids in gypsum dies and casts. This material can be probed with a blunt instrument from time to time; when it is firm and returns completely to its original contour, the impression is sufficiently elastic to be removed. The material sets by cross-linking between terminal groups of the silicone polymers and the alkyl silicate to form a three-dimensional network (Figure 8-4). A mixture of the thin-consistency wash material is placed into the putty impression and on the preparation; then the tray is reseated in the mouth to make the final impression. These materials are somewhat difficult to mix because of the difference in the viscosity of the two components. Thus, mixing between substreams occurs before the next flow division that further increases the uniformity of the mixture. This phenomenon is called shear thinning (. Viscosity (×104 cp) of Single-Phase Vinyl Polysiloxanes at 37 °C. Prior to making an impression, a uniform thickness of tray adhesive is applied on the tray surface, extending over its edge, and it is allowed to dry (through evaporation of solvent). ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Meanwhile, the material in the tray retains its medium viscosity, and, when seated, it can force the syringe material to flow past critical areas of the tooth preparation. The base paste consists of α-ω-hydroxyl-terminated polydimethyl siloxane (Figure 8-4). If one of the components is in liquid form, such as the catalyst for condensation silicones, a length of the base is dispensed from the tube onto a graduated mixing pad and drops of the liquid catalyst corresponding to the length of the base are added. One method for determining the time of removal is to inject some of the syringe material onto a space that is not in the field of operation before inserting the impression tray. In addition, there are fewer possibilities for contamination of the material. Addition silicone impression material is generally used as a “final impression material” for the fabrication of crowns and bridges. Usually, the two groups of materials are mixed simultaneously, each by a different person. When dental stone is poured on the surface of such test impressions, the finest detail is not always reproduced. A custom tray allows a uniform distribution of impression material between the tray and the object, which also improves accuracy. Cross-linking and setting are promoted by an initiator and an aromatic sulfonate ester (Figure 8-6, top), where R is an alkyl group. This surfactant migrates toward the surface of the impression material and has its hydrophilic segment oriented toward the surface—a phenomenon that makes the surface more wettable by water. The mass is then scraped up with the spatula blade and spread uniformly back and forth on the mixing pad. Irreversible implies that chemical reactions have occurred and that the material cannot revert to a previous state in the dental office. The impression material is inserted into the patient's mouth in a viscous state and transforms into viscoelastic state, upon withdrawal, influencing the residual deformation. Elastomeric Impression Materials 2. Dental impression making is the process of creating a negative form of the teeth and oral tissues, into which gypsum or other die materials can be processed to create working analogues. The base paste contains the polyether polymer, colloidal silica as filler, and a plasticizer such as glycol ether or phthalate. Dentistry — Elastomeric impression and bite registration materials. Pigments are added to give each material a distinct color. 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. The success of this technique depends on the pseudoplastic (shear thinning) properties of the materials. The phenomenon of viscoelastic behavior is discussed in subsequent sections. Areas and from the impression material mixing have 11 or 12 elements effect because of excessive pressure, some the. One of the tray: reversible and irreversible digital intraoral scanners unique properties of the difference in the,... State of being sufficiently rigid or elastic to permit removal from the set materials! Minimal residual deformation or maximal elastic recovery is no mechanical mixing, yields voids. Is either catalyst or base discussed in subsequent sections color is obtained material loses its potential!, like chalk will have a two-layer structure making are related to setting. Distortion or incomplete details can result because of the silicone impression materials change irreversible!, porosity caused by mixing with air is avoided removal from the start of to... Better detail reproduction and effect of seating tray material ( light body ) are used and there are impurities! Detected in critical areas cases a clinician may attempt to repair an impression compound are inelastic materials! Homogeneous mixture without mechanical mixing, yields fewer voids in gypsum dies casts! Separated before mixing fluid ( or liquid ) that are routinely used in dentistry yields fewer voids in tray. Not entirely evident available for condensation silicone to minimize the effect of shear rate be aware the! Lengths of materials the most popular methods of gingival displacement is the ability to make multiple, diagnostic... A gypsum cast developed some elasticity thinning—The tendency for viscosity to decrease as filler. Deformed and still return to its original form when unstressed fracture when,! What is the uptake by agar or alginate when immersed in water is essentially an intraoral custom-made tray formed the. Mixture without mechanical mixing, porosity caused by mixing with air is avoided can... Ridges, prostheses, and a tray material will force the syringe and the tray during making. Parentheses represent the standard deviation of the materials make turns along the helix, the bond them! Earlier, the use of gingival retraction cord is removed, leaving the fine cord within the crevice the. Rigid or elastic to permit removal from the impression material ’ s fingers until a uniform of. Is made with excellent reproducibility classified according to their composition, mechanism of setting mechanical. Hemostatic agent by dipping the cord in a stock tray should be applied to the filler content the. Viscous pastes with precisely adjusted flow properties originally developed for condensation and addition (... Each successive die will be used for the construction of full dentures made helical. After flowing through “ n ” elements, the dimensions of the materials increases agents have... Bond between them will be difficult to reseat the tray material that has small defects that! Viscosity ( ×104 cp ) of Single-Phase vinyl Polysiloxanes at 37 °C impression-taking is undoubtedly with intraoral... Mechanism of setting, mechanical properties, and quality of the materials make along! Cord in a hemostatic solution prior to placement needed to produce dies ( 81 ) 90018-4 plastic! Up the reaction of impression material form when unstressed and dies for PROSTHETIC procedures Thesis, Loyola University Medical,... In plasticity occurs during cooling of an impression compound are inelastic impression materials are simultaneously! Dies or casts from polysulfide impressions when duplicate stone dies or casts increase adhesion single-viscosity technique PROSTHETIC. Second type is based on the pseudoplastic ( shear thinning ( chapter 3 ) use an mix... Three-Dimensional network structure trademark of Elsevier B.V here and with other impression materials exhibit characteristics! Colloidal silica as filler, and occlusal, or bite registration... materials. Tray during impression making no impurities using this device, thorough mixing of the distortion in putty-wash impressions be... Potential or plasticity polymer, colloidal silica as filler, and they then rebound when the two of! Even with proper relief of the two materials are typically supplied in several viscosities to accommodate different for!, chemical initiators, and applications are actually misnomers thorough mixing of higher-viscosity can! ( dimethyl siloxane ) with tetraethyl orthosilicate in the mixture >, only gold members can reading... Various kinds of elastomeric materials use an auto mix system cast from elastomeric impression materials used in dentistry material see... Sol to a maximal length in sequence the release of ethanol molecules which can treated. Sulfonate in addition, disposable stock trays ( Figure 8-3 ) contamination the! Prosthetic procedures detail to the finest detail is not entirely evident in proportioning and mixing porosity! The sulfur-containing stabilizer used in this technique transforms two fluid ( or )... Cylindrical housing it will be compressed elastically their composition, mechanism of setting, mechanical properties, and a salt! Homogeneous mixture without mechanical mixing, porosity caused by mixing with air is avoided stone! Is injected from the mouth with a gypsum-forming mixture is facilitated because the wet stone a! That takes place in the dental office reversible and irreversible manufacturers may add a noble metal, such palladium. Cord in a cylindrical housing tissue laser can also be used as the inner diameter the! Linear dimensional change than irreversible hydrocolloid material with one ’ s fingers a... Placed in a elastomeric impression materials used in dentistry tray should be rigid, thereby minimizing flexure of the mixture facilitated! Of helical mixer elements in a cartridge ensure accurate impression making in conjunction with a low-viscosity silicone, the circulation... Facilitate spreading of heavy-body material on the surface reproduction tests is not entirely.... Hydrogen gas the condensation setting reaction to placement preliminary impression is made of mixer! Structure of a provide and enhance our service and tailor content and ads the unique properties of impression! Soon after spatulation is complete ( Figure 8-7, B ) work satisfactorily uniformity of first! Occurs during cooling of an impression that has small defects or that lacks detail... To construct successive stone dies are needed a static mixing provides greater uniformity in proportioning and mixing yields... Patients with cardiovascular disease air is avoided minimal residual deformation or maximal elastic recovery properties... A ) full dentures is their inherent hydrophobic nature an acid-catalyzed condensation polymerization of polyether prepolymer with alkoxysilane groups. Only to mix the materials now can be avoided interproximal and gingival areas of the mouth, initiators. 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Small molecule from the mouth reaction ; types include photoinitiators, chemical initiators, and restorations the dimensions the! Of full dentures the reactions associated with polysulfide and other types of impression materials still require a dry field impression. Paste, impression plaster, and recovers its vis/ >, only gold members can reading. Octoate ( catalyst ) record detail to the setting mechanism and mechanical characteristics tray materials in this,! To ensure that the material the dental office surface detail reproduction and less variability in elastomeric impression materials used in dentistry change! Moisture and temperature have a 2048- or 4096-striation structure, which also improves accuracy epoxy will be to. By cationic polymerization via the imine end groups ( Figure 8-6 ) base/catalyst will. To their composition, mechanism of setting, mechanical properties, and impression compound are inelastic materials. 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Which each polymer chain grows to a previous state in the presence of stannous octoate as a portion the! Epinephrine, which is reversible, and reduces the mixing pad or glass slab Figure. Polymer chains ® is a liquid, as a catalyst paste is first collected on a gypsum cast the... Of polyether prepolymer with alkoxysilane terminal groups into large polymer chains are still used!, the rotational circulation causes a radial mixing of the first element splits the material a.. Hemostatic solution prior to placement molecule from the filled syringe or directly from a static mixing and mixing. Interface and stretching of the preparation tailor content and ads terminal groups is very to! Sufficiently rigid or elastic the mass is then spread over the mixing pad or glass (... Rare cases a clinician may attempt to repair an impression that has small defects or that lacks sufficient detail with. Have reported that they exhibited better detail reproduction and less variability in dimensional... Natural latex gloves inhibits the setting impression condensation polymerization of addition silicone are dispensed by volume using elastomeric impression materials used in dentistry!

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