Considerations Common to Mainstream Dental Implant Treatment Protocols, Principles and Practice of Implant Dentistry, Impression Materials and Procedures for Removable Partial Dentures, Alan B. Carr DMD, MS, David T. Brown DDS, MS, in, McCracken's Removable Partial Prosthodontics (Twelfth Edition), B.W. Available in jars, bulk packaging and pre-measured packs. Constituents may leach out. When the impression material has set, it is removed from the mouth with the tray. Virus isolation can be done in porcine kidney, thyroid, or testicle cells; there is cytopathology, and isolates are identified with specific antisera, usually using an ELISA. It can be accomplished by using either a sectional or a single-step technique, using different types of materials. Alginate is currently one of the most popular impression materials. Two to three minutes after the surface tackiness has been lost, it can be removed from the oral cavity. Manipulation of the border tissues which demands a great Rubber-base impression material does have wide applications, and in cer- tain procedures it has … Impression/Modeling Compound, Impression Plaster Zinc Oxide Eugenol Impression Pastes (IIZ) Main types of Inelastic Impression Materials. 4. The immediate implication of this, and of reaction shrinkage in general, is that the thickness of material in the tray should be minimized. Hydrocolloid materials include agar, which is reversible, and alginate, which is irreversible. Impression materials are loaded into trays in their initial low viscous form (with the exception of impression compound) and then placed in the patient’s mouth. Elastomeric impression materials are also subject, of course, to thermal expansion and contraction. The choice of which impression material to use in each case will depend not only on the specific needs of each case, but also on the impression technique and tray to be used. (n, o) Set up for Reversible Hydrocolloid Impression Material. This classification is based on the capability of the material to withdraw over the undercuts it has set. Dentate metal perforated impression trays (, 4. Rigid impression materials include plaster and compo/zinc oxide-eugenol; however, since they cannot engage the undercuts, their application is limited nowadays. Oxygen is sometimes a byproduct of the reaction. The net effect is complicated. [Sticks]  Dry kneading with fingers. Figure 11.4 (a) Irreversible Hydrocolloid Impression material set-up. Method of disinfection 7. time to pour When a positive likeness of the arch or certain teeth is reproduced for orthodontic treatment, it is sometimes described as a model, although cast is the more proper term. Describe the Composition, setting 9 reaction, manipulation of Impression Compound. Impression materials containing an aromatic sulfonate catalyst have been reported to cause a delayed allergic reaction in postmenopausal women. Because of its high polymerization shrinkage, manufacturers make a high-viscosity catalyst commonly referred as “putty.” These putties are highly filled, so there is less polymerization shrinkage. Usually the impression material is carried to the mouth in an unset (flowable) condition in a tray and applied to the area under treatment. The catalyst contains an aromatic sulfonic acid ester and thickening agents. They are available in many viscosities and a range of colors. Hot water bath method. Soaking in warm water-bath [Sheets or cakes] Over a flame. ... flabby tissue region. Properties – Alginate Impression materials are termed “irreversible impression materials” because they will not reverse to the sol state once they react and become a gel. (h–m) Triple tray®. It sets by condensation polymerization with alcohol as a byproduct. is the short manipulation time of lo w fusing compound which . 2. Their composition includes agar, borax to improve strength, potassium sulfate to provide compatibility with the stone, preservatives, and flavoring agents. Manipulation of agar impression: The use of agar hydrocolloid involves special equipment called conditioning unit for agar. Long-term retained impression material may compromise prognosis, often severely. The tray is placed so the material is supported and brought into contact with the oral tissues, and then held without movement until the impression material has set. Wet kneading. They can be categorized as rigid and elastic impression materials. This way, any technique that allows compensation for scaling errors of these kinds at the point of final fabrication (say, mould expansion for casting, Chap. Dry kneading. Polyether impression materials tend to be more rigid than other materials. # Impression compound is characterised by all of the following except : A. warps at room temperature B. is a thermoset material C. shows increased flow when kneaded with water D. low coefficient of thermal conductivity ... C. Prolonged manipulation D. Using humidor It is thus not recommended for the fabrication of crowns and bridges. 18§4.6). The need for more satisfying impression materials promotes the development of elastomeric impression materials. Edentulous metal perforated impression trays (, 2. This, unfortunately, is in direct conflict with the recommendation for avoiding stress-set effects (§11.7). Thus, if the tray were to be at the same temperature as the impression material when that was set, with the same value of the coefficient, cooling would compensate for the impression material’s shrinkage by reducing the enclosed volume (cf. Many early versions of low viscosity PVS impression materials had excellent flow characteristics but tended to flow away from the prepared tooth after injection of the impression material. However, it does not produce very accurate surface detail, and has poor dimensional stability. Different types of impression materials are available, which vary in their properties. Courtesy Dr. Charles Mark Malloy, Portland, OR. Edentulous plastic perforated impression trays (, 3. The material is fairly stiff but very hydrophilic. Care must be taken to ensure that the water bath is not contaminated during use (Figures 11.2n–11.2o). It is set by a condensation polymerization reaction. Technique, accuracy, taste, ease of manipulation, cost, dimensional stability a… It should be noted, however, that these materials are not compatible with the addition reaction silicone impression materials and should not be used to border mold custom trays when the silicone impression materials are to be used as the final impression material. The powder is mixed with water. molding impression trays since it was introduced by green brothers in 1907. MATERIALS DEFINITION “Impression is defined as negative likeness or copy in reverse of surface of an object, an imprint of teeth and adjacent structures for use in dentistry.”. Secondary impression can be made by using low fusing impression compound (green stick) ... by using tissue function or manual manipulation of the tissues to shape the border area of an impression material. In case of mandibular impression the tray is centered exactly over the ridge and seated straight down. IMPRESSION. The clinical impression technique and the production of the cast vary with each impression material. – A multitude of waxes are used in dentistry. (f) Step 5 – Water mea/>, 1. Alginate impression (A) and gypsum stone cast (B). Polysulfide rubber is still used in many countries because it is inexpensive and has plenty of working time. The base contains a polysulfide base polymer, fillers, and plasticizers. Frederick C. Eichmiller, Carlos A. Muñoz-Viveros, in Contemporary Esthetic Dentistry, 2012. Polyether rubber was developed in the late 1960s and is characterized by a relatively short working time but achieves great accuracy. The polyethers have low to moderate tear strength and much shorter working and setting times, which can limit the usefulness of the material. The impression compound was gently pushed to fill the defect (Figure 2) and withdrawn when half set as it might be difficult to withdraw the completely set hard impression compound from the undercuts. However, this is affected by the filler content in the normal way (6§2.1). Charles M. Weiss DDS, ADAM WEISS BA, in Principles and Practice of Implant Dentistry, 2001. After the appropriate contact time the impression can be removed, rinsed thoroughly with tap water, shaken gently to remove adherent water, and poured. The cast is made by filling the impression with dental stone or other model material or by scanning the impression and printing a plastic model from the digital impression (see Chapter 14). (d, e) Dentate plastic perforated ‘stock’ trays. – They have advantages and disadvantages similar to those of reversible hydrocolloid materials because both types of materials are predominantly water. The tissue will quickly recover if this is done in a timely manner. Fig. manipulation 2. Casts (positive reproductions) are created from dental impressions and are used to fabricate various dental prostheses. These characteristics can limit the use of polyethers in removable partial denture impression procedures. According to the ADA specifications number 3, the Green stick compound is a Type 1 Low Fusing Impression Compound. Three … The impression material will set chemically or physically and then may be removed from the mouth for use extra orally. Impression compound (Hard) 450C Impression compound (Soft) 370C Manipulation: • As impression compound is of low thermal conductivity, adequate time should be given for uniform heating to INCREASE flow during impression taking. Plaster, impression compound, zinc-oxide–eugenol, and other materials were originally developed as inelastic impression materials. These are generated by mixing a base paste consisting of nanofillers, polymers of silicone, cross-linker, and inhibitor with a catalytic paste, consisting of platinum catalyst and plasticizer. Courtesy Dr. Charles Mark Malloy and Dr. Kyle Malloy, Portland, OR. Fig. Again, we are faced with a compromise because of unavoidable sources of error. (b) Step 3 – Painting the stock tray with adhesive on an impression tray prior to use. The flow characteristics and flexibility of the polyether materials are the lowest of any of the elastic materials. The stiffness of the material can result in cast breakage when removal of the cast from a custom tray is attempted. These materials should be able to produce an accurate replica of the intraoral structure, to prevent deformation and be atraumatic when removing from undercuts; they should also have proper setting time and biocompatibility. The fillers are mainly zinc oxide, titanium dioxide, or zinc sulfate. These materials have a much lower chance of permanent deformation when removed and are able to reproduce the surface detail very accurately, but they are hydrophobic and therefore contamination of saliva will result in loss of surface detail to some degree. (A) Mandibular and maxillary rim-lock impression trays. In Craig's Restorative Dental Materials (Fourteenth Edition), 2019. MANIPULATION: 1. However, as soon as appreciable elasticity develops, distortion must develop as the expansion will be constrained. The irreversible and reversible hydrocolloids, modeling compound, plas- ter of Paris, waxes, and zinc oxide and eugenol pastes have been used with great success. It is then moved upward and backward direction. Modifications can be done with wax, tracing stick impression compound, or heavy-bodied silicone, depending on the operator’s convenience. Properties : Technique, accuracy, taste, ease of manipulation, cost, dimensional stability and the operator’s preference will dictate the choice of impression materials (Figure 11.1). Inelastic: impression compound. Prolonged immersion or over heating not recommended. – Alginate materials are […] These are used with heavy body materials in a tray to provide more rigidity to the impression and assist in forcing the low viscosity material into the gingival sulcus and accurately and completely capture the prepared cervical margin. The tray with the impression material is then removed from the mouth, and the impression is ready for disinfection and pouring with a cast material to make a positive replica. Once an impression is removed from the patient’s mouth, the following procedure should be undertaken: When receiving laboratory work, disinfect and rinse prior to inserting into the patient’s mouth. Wash in a designated sink to remove the same, The disinfection process will be impeded without adequate removal of blood and/or debris, Follow the manufacturer’s instructions in relation to the immersion of the dental impression in a disinfectant solution for material compatibility and length of immersion, After impression decontamination, rinse impression in the designated sink, It is essential that good cross-infection control practices are followed during impression decontamination; avoid contamination of immersion bath and sink. (g) Custom/special tray. Copyright © 2021 Elsevier B.V. or its licensors or contributors. Although rarely used today, reversible hydrocolloid impression material is the least rigid of all impression materials and may be the material of choice when making impressions of multiple prepared periodontally involved teeth. on applying heat, it softens and on cooling it hardens. It is necessary to decontaminate impressions to prevent cross-contamination. Such impression materials are referred to as duplicating materials (for additional information refer to website http://evolve.elsevier.com/sakaguchi/restorative). From: Little and Falace's Dental Management of the Medically Compromised Patient (Eighth Edition), 2013, Frederick C. Eichmiller, Carlos A. Muñoz-Viveros, in Contemporary Esthetic Dentistry, 2012. If clinical examination leads to suspicion of retained impression material as the cause of a tissue reaction, explore carefully and remove any retained impression material that may be found. Setting Time 5. (B) Custom impression tray. Figure 11.3 (a) Hydrogum® – Ahermack. (b) Xantalgin® Select – Heraeus. The application of dental impression compound has also decreased with the increased use of rubber impression materials, which can also be electro-formed to produce metal dies. The base is composed of a polydimeththylsiloxane, orthoalkylsilicate for cross-linking, and inorganic fillers. It is also worth nothing that the tray material also has an appreciable thermal expansion coefficient. Impression materials are also classified as reversible (compounds and hydrocolloids) or irreversible (silicones, polyethers, and alginates). Softening of impression compound. The catalyst or accelerator contains lead dioxide, hydrated copper oxide or organic peroxide as a catalyst, sulfur and dibutyl phthalate as a plasticizer, and other nonessential fillers. Needless to say, distortions arising from any of these sources of error cannot be compensated, as was discussed above (§9.1). 12.1. Impression materials need to flow readily into the minute details of cavity preparations and accurately capture grooves, pinholes, and cervical margin detail. 3§4.14). (Adapted from the Cross Infection Control Policy, Dublin Dental Hospital, 2010.). In Fenner's Veterinary Virology (Fifth Edition), 2017. PVS offer advantages of improved hydrophilic nature and thus better flow precision and accurate detailing (Kumar and Vijayalakshmi, 2006). The use of agar hydrocolloids is complicated by the need for a tempered water bath and prefabricated metal trays (Figure 2-34). They may be perforated for better retention of the impression material. Impressions are used in the dental surgery to produce accurate (varying degrees of accuracy) negative reproductions of the patients’ teeth, surrounding tissues and dental arches. Greenstick compound is one of the impression materials used during one step in the impression making for the complete denture preparation. (c–e) Step 4 – dispensing the powder. Alginates or irreversible hydrocolloids are the most widely used impression materials in dentistry. A snap-removal technique is required to minimize permanent deformation. While the tear strength of polyether impression materials is excellent, the amount of force required to remove the rigid impression may exceed the tear strength of the material. The properties of custom trays are discussed later in this chapter. It is mixed with water to achieve the desired mixture. For example, for typical addition silicone products, the value steadily decreases in progressing from ‘light’, through ‘medium’ and ‘heavy’ body to ‘putty’ materials, reflecting the steadily increasing volume fraction of filler. They are composed of a powder containing sodium or potassium alginate, calcium sulfate as a reactant, sodium phosphate as a retarder, fillers such as diatomaceous earth, potassium sulfate for stone compatibility, and flavoring agents. Because water is a byproduct of the reaction, the impression must be poured within 30 minutes. There is no manipulation needed for agar impression materials, but a special water bath with three compartments (Figure 11.1n) is needed to facilitate the use of this impression material. Figure 11.2 (a) Edentulous metal impression trays. Kneading improves plasticity. A measuring scoop and water measure are included with the alginate materials. Proportioning 2. [T Table 1] shows the properties of different elastomeric impression materials. In any case, setting shrinkage cannot be compensated thereby. Manipulation of ZOE Impression Paste. Casts of the mouth are used to evaluate the dentition when orthodontic, occlusal, or other problems are involved, and in the laboratory fabrication of restorations and prostheses. Set PVS materials are relatively rigid but seem to fall below the threshold where problems with fracture of dies are common. Agar impression materials have been largely replaced by rubber impression materials. While the material is warming, whether from the heat of reaction or from contact with the mouth, and it is still fluid, there will be no adverse effects. It is supplied as a base and catalyst pastes. After removal, the impression compound bulb was inserted and removed repeatedly so as to acquire the desired shape of the defect. Elastomeric materials include polysulfide, polyether, condensation-cured silicone, and addition-cured silicone. Some have an unpleasant taste, and because the material will absorb moisture, it cannot be immersed in disinfecting solutions or stored in high humidity for any extended period of time. Stick compound is preferable as wax is nonrigid. Wax and Impression Compound A. Wax – Wax was probably the first impression material used in dentistry. This can present a problem with long, thin preparations of mandibular incisors or periodontally involved teeth. 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