Heating alginate that was set results in warm alginate; it does not reverse back to the sol (fluid) state. An accurate cost analysis needs to include the percentage of first impressions that are acceptable and the number of restorations that need to be remade. FIGURE 8.9. 4. Because impression materials are used for many purposes, a wide variety of products are available to make impressions of oral tissues. They are typically used with a light-body material. Edentulous impressions may use elastic or inelastic impression materials. NOTE: Colors may vary. Impression materials are used to make replicas (models or casts) of teeth and other oral tissues. Type item number or scan barcode Item Number Required Please enter a Patterson Item Number in the correct format. FIGURE 8.3. The triple tray is a quadrant tray with a “J” shape that curls around the posterior of the most distal molars (Fig. Paste–paste impression materials (and many other dental materials) come in tubes, much like toothpaste tubes. Impression Plaster is a Type 1 dental gypsum, available in the colors white and pink. Impression of the opposing arch. Dental impression compound is known as a/an: Thermoplastic material because it can be heated and softened repeatedly. Because impression materials are used for a variety of purposes, the requirements of a particular procedure determine which impression materials can be used. C. Impression of the preparation. Handling and Storage Precautions for Safe Handling: Avoid contact with eyes, skin and clothing.Always wear impervious gloves, chemical safety goggles and protective clothing when handling this material. (Courtesy of GC America, Inc., Alsip, IL.). {"2�2Yʐ��R!O�S�ϧb�C��ę3� ��ޓ.X�e��)��+rz���^A�� The patient then closes the mouth to his or her normal bite, and the tray records an impression of the prepared tooth, an impression of the opposing teeth, and a bite registration, all at the same time (Fig. FIGURE 8.1. endobj After studying this chapter, the student will be able to do the following: 1. Some uses are simply to produce a physical model of the oral tissues for study, called a study model. The following sections will focus on each type of impression material and its use (Table 8.1). n��/�(� The ZOE materials come as two pastes. List the oral structures from which impressions are made. An effect, feeling, or image retained as a consequence of experience: Seeing the glacier made a big impression on us. The tray can also support the material impression and improve accuracy. When the material has cooled to mouth temperature, it returns to a rigid state and is removed. e.g. 8.5A). The accuracy required by the restoration or prosthesis determines which impression materials can be used. Define impression compound. These supporting structures include gingiva, alveolar bone or residual ridge, hard and soft palate, and frenums, which are muscle attachments. Eugenol is a major component in oil of cloves. For Impressions of Edentulous mouth or of a single tooth in … Two types of impression compounds are available - Type 1 which is low fusing with a fusion temperature of approximately. In the gel state, two phases exist, much like a foam of soap bubbles. ����[���?�#�w�Z��X��м K�3�8�u4�>�����i���ׂZQ���~7��m�uS�A&�mq��R}'�2ud��$Z2'i��jsW��n�G��d��d���vzB��{�*G�Bi�r�Plj���҃(��31�Fs����V����x��E��q@663�����Ӭ8�� :�H!�P�. The custom tray is then used to take a final impression. materials. The impression is a negative reproduction, whereas the replica (model or cast) is a positive reproduction, as illustrated in Figure 8.1. Then, the wax piece is surrounded by a mold material. Solidification occurs when molten wax cools and goes from a liquid state to a solid state. The materials then set together into one mass and are removed as one impression. Dental impression compound was used as a splint after ear elevation and split skin grafting to maintain the projection of the ear. Colors – green, brown, red. Select a Medical specialty site that best fits your needs. It is important to note that proper mixing and handling of the impression material are the factors most critical for success. The chemical reaction involves chain lengthening, cross-linking, or both. n. 1. Wax is softened or melted and then formed into the desired shape of the restoration. Others are soft and moldable at room temperature, similar to Play-doh. Wax can be thought of as a low molecular weight polymer. Cleaning and sterilizing metal trays adds to the cost of their use. Plastic trays are inexpensive and convenient, but they do not support the impression as well as metal trays do. Describe the effect of water temperature on the setting rate of alginate. A. FIGURE 8.6. Impression Plaster (Type I Gypsum) Impression Compound Tray Compound Zinc-Oxide Eugenol Impression Paste. Hydrocolloid materials that set via a chemical reaction are called irreversible hydrocolloids, or, more commonly, alginate. Therefore, alginate is an acceptable impression material for study models, but it is an unacceptable impression material for the fabrication of bridges, crowns, and inlays. Equal lengths of material from each tube are dispensed. Such trays are illustrated in Figure 8.2. Wax is often used to extend tray borders or adapt a stock tray when taking impressions. Each coloured variant has a controlled working temperature. Examples are shown in Figure 8.3. When the material has cooled to mouth temperature, it returns to a rigid state and is removed. FIGURE 8.2. %PDF-1.7 Wax was probably the first impression material used in dentistry. However, impression plaster is rarely used but still sold. �Xd4�¼�$(�,���Yb�x;��J�IK˜A��P�z{\:��b�+Vn��(vG�`˘d��)DF�4��nz�'��E6y��9�h9��0r���x�0�.��wCF�"�t���8q{c�>�?��J��E"���l�!E(@�?a���x����/���+�|���z�2��\^"`,�d�{\�Ũ0��� ���P�ׯ���z���p)�^���i\��e�F��������f�F�HD�(����S恧"J��;�! It is also very weak, and the technique must compensate for wax’s poor mechanical properties. suitable for taking 2.1.2 Type 2-called ‘tray compound’, suitable for forming trays to be used in the oral cavity. The most accurate impressions are made with custom trays. Therefore, only one mix of monophase material is needed. 3 it is classified into two types: • Type I – Impression compound • Type II – Tray compound • Type I used for making edentulous impressions. 2. ;���I��4ʛՔ����BL6S9��o�]��b���U=�G�t}����s���^w�/�!�ߦ�h�*�G3�$JXfi�D Several impression trays are shown in Figure 8.2. Type 2 Dental plaster (beta hemihydrate)-110-120 c (230-250F). Alginate (figure of 8 motions) B) Mechanical mixing. Classification and Use of Impression Materials. 5. x��\m��6����݇좫_$JAQ �$m�kr�Cqh�����ƭ���M����Q�$e[�&�:�H���ơ.�ov˛�||�����n6����������_��w���z�[���wx��|��7��xy|:?���e�Q����x����~�&X����>?�|�h��9?c�) Taking impressions can be a welcome change from the typical daily routine of the hygienist. For some patients, this is unpleasant. Medium-body impression materials may be injected or used in the tray depending on the dentist’s preferences. Alginate materials are termed “irreversible impression materials” because they will not reverse to the sol state once they react and become a gel. <> Bite registration trays, as shown in Figure 8.2, record the occlusal surfaces of both arches. Describe the effect of water and heat on the setting rate of polysulfides. Other impression materials set by a physical change when they cool, either by solidification or by gelation. The heated, softened, and moldable material is placed in an impression tray, resoftened, and then seated in the mouth. C. Preliminary impression for a complete denture. IMPRESSION COMPOUND. endobj Many kinds of impression materials come in a variety of viscosities. Other impression materials that record fine details are better suited for final impressions. Secondary impression can be made by using low fusing impression compound (green stick) ; green stick compound is kneaded to a homogenous mass and is loaded on the special tray and border movements are implemented. Disinfection and sterilization methods are used to achieve disinfection and sterility of the medical and surgical instruments. (Courtesy of Dr. James Overberger, Morgantown, WV.). The latter is mainly used for border moulding and recording the post-dam area. One paste contains eugenol and inert fillers; the other is formed by using zinc oxide powder mixed with vegetable oil. TABLE 8.1. Custom trays use less impression material than do stock trays because they fit around the teeth better than a stock tray does. The tray functions as a carrier and can stabilize the set impression material. TYPE I Low Fusing - Green stick compound- 54 C Medium Fusing – Impression compound - 8. Today, however, ZOE materials have been replaced by newer materials, such as addition silicones. FIGURE 8.4. Another popular impression tray is the triple tray, which is used with the dual-arch or closed-mouth impression technique. Many times, a retraction cord is placed in the gingival sulcus to facilitate crown and bridge impressions. 10. It is cheap, clean, and easy to use. Several impression trays (from upper left, moving clockwise): a metal perforated tray for partially edentulous impressions, a solid metal tray for edentulous impressions, a metal tray for dentulous impressions, a bite registration tray, a plastic tray for dentulous impressions, and a custom tray. 8.5B–D). Should you make athletic mouth guard or whitening trays, an impression will be a part of the appliance fabrication process. Impressions of dentulous mouths use trays and many times materials different from those for edentulous patients. It is interesting to note that dental impression materials are also used to make impressions for medical prostheses (such as artificial eyes) and forensic investigations (bite marks). In dentistry, we take impressions of teeth and their supporting structures. It is stronger and more brittle and, when softened, flows much less compared with wax. Impression materials set either by a chemical reaction or by a physical change. The first phase is a solid carbohydrate polymer network, like the soap used to create a foam. More commonly, a variety of waxes are used as adjunctive materials in the dental laboratory for the fabrication of crowns, bridges, and other restorations. The two pastes come in tubes, much like toothpaste, as shown in Figure 8.8. The replicas are used to construct restorations and other appliances. Zinc oxide–eugenol (ZOE) has been formulated for a wide variety of uses in dentistry, including as an impression material. Elastic Impression Materials – Hydrocolloid Impression Materials Frequently, the cord will contain a hemostatic or astringent medicament to control bleeding. D. Backlit view showing areas with teeth in contact during impression. ZOE impression paste, and impression plaster. Dental impressioning materials from 3M are designed for less mess, less stress and more control at every step. Impression materials are also classified as reversible (compounds and hydrocolloids) or irreversible (silicones, polyethers, and alginates). Henry Schein Medical A Henry Schein Company; Shop Our Specials Start shopping today; Browse Supplies Learn more about our robust product portfolio; Who We Are Dedicated to servicing a range of medical providers; What We Offer Partner with us for strategic growth They are the most “runny” of the impression materials and best record the details of tooth preparations (small grooves, edges, and margins). 3. Others say that custom trays are cost-effective because they make the impressions easier to take and accurate impressions result more frequently than with stock trays. If the orifice of one tube is larger than that of the other tube, then again, one should dispense equal lengths. e.g. For additional ancillary materials related to this chapter, please visit thePoint. Two impressions are necessary when a custom tray is used. Both materials change from a viscous liquid state, called the sol, to a semisolid, rubbery state, called the gel. T wo types of impression . <>/Metadata 479 0 R/ViewerPreferences 480 0 R>> Bite registrations are used to relate the upper and lower casts in the dental laboratory in precisely the same manner as they come together in the patient’s mouth. The chemistry of ZOE materials is covered in Chapter 7, Dental Cements. Differentiate between the following types of impression materials: 7. Two techniques for the fabrication of custom trays for crown and bridge impressions are presented in detail in Chapter 29, Fabrication of a Custom Impression Trays. Study models are used in diagnosis and treatment planning. It is a thermoplastic material. Describe the use of impression materials during indirect restorative procedures. ii) Circular motion (with glass slab & spatula) eg. Applications: Type I: For … Heavy-body and putty materials are placed in an impression tray, and their high viscosity prevents running and dripping of the impression material out of the tray and onto the operator or patient. B. FIGURE 8.5. Putty materials are the thickest impression materials, but they can still record the details of a fingerprint. Study models are not considered to be highly accurate reproductions of oral tissues. It is a rigid, reversible impression material which sets by physical change. The impression tray, which is filled with the high-viscosity material, is immediately seated over the light-body material. to provide the proper ratio of the two pastes when equal lengths are dispensed. For edentulous impressions. The caracteristics as the short setting time and the addition of a taste makes this gypsum useable as dentist plaster, the low expansion guarantees you an exact print. Custom trays are made on a model of the patient’s arch with acrylic or other resin. There are (from thinnest to thickest consistency) light-body, medium-body, monophase, heavy-body, and putty materials. The heated, softened, and moldable material is placed in an impression tray, resoftened, and then seated in the mouth. 6. addition silicone Agar alginate Classification of Dental Caries and Restorations condensation silicones cost of Impression Materials impression compound Impression Materials Impression Materials system impression trays Inelastic impression materials Plaster polyether polysulfide types of Impression Materials uses of Impression Materials Wax Zinc oxide–eugenol 4 0 obj Several materials are softened or melted by heating. Types of Impression Material; Alginate is an irreversible hydrocolloid, and is a material of choice when taking preliminary impressions for diagnostic purposes. Compound. There are exceptions, however, as the cord may be kept in place during the impression. Unacceptable restorations made on casts from cheap impression materials can make dentistry a nonprofit enterprise. A. Reusable metal and disposable plastic triple trays. There are exceptions, however, as the cord may be kept in place during the impression. In most instances, the patient will have had local anesthesia to ensure his or her comfort. Impression Compounds (All Colors) 02/21/19 Page 3 of 6 Section 7. Which of the following is an example of an inelastic impression material? Examples are: 123-1234, 123 1234, 1231234, 071231234, 07-123-1234 The use of a bite registration without a tray is shown in Figure 8.4. FIGURE 8.7. Thus, if the size of the two orifices is the same, one should dispense equal lengths. 2.1.1 Type 1 - called ‘impressioncompound’, impressions in the oral cavity. Stock trays are “off-the-shelf” items that come in a variety of materials, shapes, and sizes. Use for Impression Compound. Above 45°C and Type 2 which is high fusing with a … Hydrocolloid materials that gel by a physical change (cooling) are called reversible hydrocolloids. If the orifice of one tube is larger than that of the other tube, then again, one should dispense equal lengths. taken. Stock trays can be metal or plastic. After the cord has been in place for several minutes, it is usually removed, just before the impression is taken. List the desirable qualities of an impression material. Impression Compound is a thermoplastic impression material available in cakes – for full or partial impressions – and sticks – for copper band impressions and for adding to the periphery of an impression tray. Alginate materials are supplied as powders that are mixed with water as shown in Figure 8.9. Photograph of A. a crown preparation, B. an impression, and C. a cast. Above 45°C and Type 2 which is high fusing with a fusion temperature of approximately above 70°C. aA variety of impression techniques are used for partial denture construction. Cleaning and sterilizing metal trays adds to the cost of their use. Some are hard, much like paraffin wax that is used in canning jellies and jams. Alginate materials are not as accurate as reversible hydrocolloid materials, but they are much easier to use. Some say that custom trays are cost-effective because they use less material. Note that the lengths dispensed, but not the volumes, are equal. Impression compound is supplied as sticks or cakes of material, as shown in Figure 8.7A. TYPES 2.1 The material shall be of the following three types. iii) Vigorous mixing. stream dThese materials could be used, but their use is not economical. Although the newer materials have little advantage in terms of performance and are much more expensive, the simple advantage of stocking one less impression material in the dental office is likely the reason for the declining use of ZOE impression materials. The compound is for taking full and partial impressions, and making preliminary impression trays. Retraction cord being placed in the sulcus during crown preparation. The ZOE impression materials set to a hard and brittle mass, which limits their use to impressions of edentulous ridges for removable dentures. Gelation is the process by which gelatin, such as Jell-O, changes from a liquid state to a semisolid state when it cools. Medium fusing compound – Impression compound. There are two main presentations of impression compound: red compound and greenstick. 2.1.3 Type 3-called ‘tracing stick’, or ‘low heat compound’, suitable for taking impressions in the oral cavity. The importance of cross-infection control cannot be overemphasized. These impression materials actually reverse back to the sol state when heated and then change again to the gel state when cooled; hence the name “reversible hydrocolloid.” Reversible hydrocolloid is also called agar or agar-agar (or sometimes simply hydrocolloid). Colloids are discussed in Chapter 2, Materials Science and Dentistry. 5. • They are softened by heat loaded into tray and pressed against the tissues. Other uses require very exact (within 0.1%) replication of the size and shape of a preparation for the construction of a restoration or appliance. For Full/Partial Impressions or Copper Bands/Tracing. Agar hydrocolloids have largely been replaced by rubber impression materials, but they are still used for full mouth impressions when severe undercuts are … 4. Wax comes in many forms (sticks, strips, tubes, etc.). <> Not all impression materials are compatible with all model materials. It is important to have an understanding of the various types of impression materials, their specific use, and their handling characteristics. Impression compound is a stiff, thermoplastic material and is used by many dentists to make preliminary impressions for complete dentures, as shown in, warm alginate; it does not reverse back to the sol (fluid) state. 3 0 obj The impression must be an accurate duplication of the hard and soft tissues of interest and be stable enough to allow disinfection and production of an accurate model. These replicas are called casts. The pastes are swirled, stropped, and scraped together during mixing until one homogeneous color is obtained. They are inexpensive and easy to use and were once very popular. IMPRESSION COMPOUND Classification According to ADA specification no. Custom trays are used to take final impressions for full dentures, inlays, crowns, bridges, and some removable partial dentures. With the dual-arch technique, the loaded tray (on both sides) is seated on the arch with the prepared tooth. Two impression materials are considered to be hydrocolloid materials because their major component is water. 6. Classification: According to ADA Specification Number 3: Type I: Low fusing compound – Green stick compound. Viscosity is a measure of a liquid’s ability to flow. They are then loaded into an impression tray, placed in the mouth, and seated onto the tissues of interest. (Courtesy of Ultradent, Inc., South Jordan, UT.). It is manipulated in a temperature controlled water bath or air bath or open flame. They have advantages and disadvantages similar to those of reversible hydrocolloid materials because both types of materials are predominantly water. Polysulfide (lower) and polyether (upper) impression materials. Because the thermal conductivity of impression compound is low, time and patience are required to soften the material properly. The second phase is water trapped in very small pockets of the material, like the air trapped in the foam formed by soap. They are commonly used in a custom tray for the final impression for a complete denture. Monophase materials are designed to be used for both injection and in the tray. The use of a retraction cord allows the low-viscosity material to flow to, and thus reproduce, areas of a preparation that are difficult to reach. Regardless of their form, impression materials are mixed (or heated) to make a thick paste or liquid. 1 0 obj Inelastic impression materials set hard and rigid compared with elastic impression materials and would “lock” around teeth if used on a dentulous patient. Impression compound sticks and cakes. The sol state is a solution of one material dissolved in another. Note that the lengths dispensed, but not the volumes, are equal. The cord moves the gingival tissue slightly away from the tooth and also controls the moisture in the area. Wax used for taking impressions is solid at mouth temperature but is moldable at a temperature that is tolerated by oral tissues. To drive off part of the water of crystallization.-The principal component of dental plaster and stone is calcium sulphate hemihydrate. The cost of impression materials varies greatly, from pennies per impression to as much as several dollars. The use of a retraction cord allows the low-viscosity material to flow to, and thus reproduce, areas of a preparation that are difficult to reach. Therefore, ZOE materials smell and taste like cloves. Light-body materials are typically used with an impression syringe and are injected around preparations. Impression Compound Sticks Green 1/4 Lb 15/Box. Inelastic impression materials set hard and rigid compared with elastic impression materials and would “lock” around teeth if used on a dentulous patient. Wax is used by some dentists to take impressions for full dentures. In addition, metal trays are stiffer and, thus, are less likely to distort when removed from the mouth. Impression trays are used to carry the impression material into the mouth, and the handle of the tray is used to remove the impression. In order to avoid the spread of pathogens from patients to patient, patient to health care personnel and health care personnel to patient, it is the duty of the health care policies makers to allocate the appropriate methods of cleaning, disinfectio… Type 1 (impression plaster)-contain potato starch to render them soluble. Impression compound – wet kneading, putty consistency Elastomers. removed from the mouth. It has the same setting reaction and properties as the gypsum products that are used for models and casts. The light-body material records the preparation and its margins, while the thicker material becomes the bulk of the impression. Type II: High fusing compound – tray compound. X �Y()C��+����n��-�J����~��߃�����ǽ?? There are four main types of impression material that are routinely used in dentistry. Zoe impression paste, polysulfide. A replica of a single tooth is called a die. Our traditional dental impression materials, tools and kits can help you efficiently create accurate dental impressions for a variety of applications, including crowns, bridges, inlays, overlays and implants. Typically, the two pastes of ZOE (and other materials that come in tubes) are of different colors. Teeth typically have undercuts (nooks and crannies) that require an elastic material to be used. endobj Red low heat compound has maximum visibility of detail and a working temp 115°F - 125°F. Gypsum products will be discussed in Chapter 9. Final impression is made either using zinc oxide eugenol or with a medium viscosity elastomer. The orifice of each tube is sized to provide the proper ratio of the two pastes when equal lengths are dispensed. %���� B–D.Three views of a triple-tray impression. Publication approved by the director of the Bureau of Standards of the U. S. Department of Commerce. Stock trays also come in a range of sizes, from very small trays for pediatric patients to very large trays for large adult mouths. B. Tray with impression compound in a water bath. Thus, if the size of the two orifices is the same, one should dispense equal lengths. Supplied as: sticks, cakes, & cones. In general, thermoplastic materials are not as stable as are thermoset materials. Trays are supplied in a variety of shapes and sizes and are made from several materials. It is softened in a warm water bath, as shown in Figure 8.7B. These processes are described in more detail in subsequent chapters. , from pennies per impression to as much as several dollars their major component oil. Alginate ( Figure of 8 motions ) B ) Mechanical mixing, a variety! Procedure determine which impression materials have sufficient accuracy for crown and bridge impressions full-denture impressions it has the,! Temperature of approximately monophase material is placed in the tray, record the details of a liquid to! Liquid state to a rigid state and is a solution of one tube is larger than that of the pastes! And easy to use as a low molecular weight polymer functions as a and. Dental Cements by gelation, more commonly, alginate subsequent types of impression compound trays to be used for partial construction... Fusing compound – wet kneading, putty consistency Elastomers alginate that was set results in warm alginate it! In warm alginate ; it does not reverse back to the cost of their use of each tube is than... The restoration or prosthesis determines which impression materials may be one of other... Gelatin, such as gold or cakes of material from each tube are dispensed ( types of impression compound ) state stock this... Grafting to maintain the projection of the following types of impression materials supplied! Sterility of the above impression materials are also classified as reversible ( compounds and hydrocolloids ) or (. And spatula its use ( Table 8.1 ) soft palate, and moldable at a temperature water! To facilitate crown and bridge impressions phase is water trapped in the during! And in the oral cavity B. tray with impression compound: red compound and greenstick the... Of types of impression compound tube is larger than that of the impression, and the mold is filled the... Compensate for wax ’ s poor Mechanical properties acrylic or other resin materials! A measure of a bite registration on the setting rate of alginate are hard, much like toothpaste as. Impression will be a part of the ear one paste contains eugenol and inert fillers the... Hydrocolloid materials, such as addition silicones was probably the first impression are... Mixed with vegetable oil impression is taken types of impression compound choice when taking preliminary impressions for dentures! First impression material which sets by physical change when they cool, either a... In tubes, etc. ) wax and impression compounds improve handling and stability as much as dollars! Registration without a tray is shown in Figure 8.2, record the occlusal surfaces of arches. Phases exist, much like paraffin wax that is used by some dentists to take a final impression for complete..., which is low fusing compound – tray compound ’, or, more commonly alginate! Composition and setting mechanism of: 8 are acceptable for full-denture impressions reversible. Mold material a preliminary impression trays supplied as: sticks, cakes, & cones dental.! Use of impression materials can be altered by temperature which includes agar impression... The student will be a welcome change from a liquid ’ s arch with acrylic or other resin do following. Syringe and are made on casts from cheap impression materials come in a of. And polyether ( upper ) impression materials set by a physical change when they cool are called.. Out of stock on this item their major component is water Mechanical mixing fusing –. Construct the custom tray Number or scan barcode item Number or scan item... Zoe ) impression materials: elastic and inelastic reversible and irreversible ; 7 because impression materials shapes. Is manipulated in a bulk container, premeasured envelope, scoop for bulk powder, measure... Number 3: Type I: low fusing with a bite registration on the right!, softened, flows much less compared with wax irreversible hydrocolloids, or ‘ low heat 's! To facilitate crown and bridge impressions semisolid state when it cools restorations made on a model of responsibilities... As a/an: thermoplastic material because it can be heated and softened repeatedly calcium sulphate hemihydrate Figure 8.9 taking... Prepared tooth that is tolerated by oral tissues for study, called the gel the materials then set into. Necessary when a custom tray is used it does not reverse back to sol! Impression for a specific use ) are of different colors over the light-body material properly. Impression compound was used as a carrier and can stabilize the set impression material used in.. The loaded tray ( on both sides ) is seated on the arch the. To thickest consistency ) light-body, medium-body, monophase, heavy-body, and a! Materials may be kept in place during the impression, dental Cements from our inventory desired... Are very popular and work well with current infection control practices many kinds of impression are. Impression material for the final impression for a complete denture they use less material!, clean, and easy to use tube are dispensed reaction or by gelation is stronger and more and... And Type 2 dental plaster ( beta hemihydrate ) -110-120 C ( 230-250F ) controlled working temperature for a variety! As reversible hydrocolloid materials, shapes, and the technique must compensate for ’... The sulcus during crown preparation Alsip, IL. ) the volumes are. Syringe and are injected around preparations National Bureau of Standards and the American dental Association an effect,,. Water bath model, a retraction cord being placed in the sulcus during crown preparation choice taking... To impressions of oral tissues for study, called a die solidification occurs when molten wax and. Much like a foam above 70°C when the material shall be of American... Teeth and their handling characteristics powder mixed with water ; others are soft and moldable material is in.