impression materials classification

Classification of Impression materials. The ability of impression materials and gypsum products to reproduce detail in the cast is normally determined by measuring the contact angle which a drop of aqueous calcium sulphate solution makes with the surface of the impression material. Dental Materials PRIME. Let's understand the properties, behavior, uses, and manipulation of the various materials used in dentistry.. all simplified, just for you! Once positioned in the patient’s mouth, the materials undergo ‘setting’ by either a chemical or physical process. Start studying Impression materials. Figure 16.5 shows diagramatically the way in which a set material is placed under stress during the withdrawal of the impression. But retention is not good for mucostatic impression technique. Zoe impression paste, Impression plaster. Can wear Dentures overnight invites Denture Stomatitis? 4 Classification of agar hydrocolloid impression materials. Dentist must know the impression materials used for specific condition. It should be remembered however, that viscosity often varies with the applied stress (p. 19). Figure 16.1 gives a simplified classification according to viscosity in which materials with the highest viscosity are shown at the left of the figure and those with the lowest viscosity are shown on the right. This results in thermal contraction, the magnitude of which depends on the value of coefficient of thermal expansion of the impression material and impression tray to which it is attached. This may effect the fine detail which can be recorded in impressions of hard tissues and may influence the degree of tissue compression or displacement achieved with soft-tissue impressions. An impression is imprint of the mouth. As per the name it imparts compression forces on mucosa.Hence, it is also known as Definite pressure impression.Since,it is applying compression forus to oral tissues,this technique ,has good retention While chewing.Material of Choice for Mucocompressive impressiontechnique includes Impression compound,Soft liners. (a) The tray contracts and reduces the impression space. (b) The impression material contracts towards the tray (providing it is bonded) and increases the impression space. Impression technique A method and manner used in making a negative likeness. Dental impression.Materials. 16.3. This is illustrated in Fig. The term elastic as applied to impression materials is fairly unequivocal since the materials which form this group all possess the ability to be stretched or compressed and give a reasonable degree of elastic recovery following strain. Based on setting of materials … a) Rigid. As the name signifies Muco static means no pressure is applied On the tissues while taking Impression. Classification of impression materials. It is very important for us to understand taking a good impression using a correct impression technique. Fig. (b) Contraction results in an oversized impression space. Many dental appliances are constructed outside the patient’s mouth on models of the hard and/or soft tissues. Impression materials: basic properties Gen Dent. It may be less confusing if the terms rubbery and non-rubbery were used instead of elastic and non-elastic. Before setting, the property most normally used to characterise materials is viscosity. In cases where the impression is made from a hydrophobic material the hydrophilic slurry of calcium sulphate hemihydrate in water may not be able to approach closely enough to the surface of the impression (on a microscopic scale). Additional retention is achieved by using perforated trays. Establishment of the classification of and specification of the requirements for impression materials in powder form containing an alginate as the gel-forming ingredient. Elastic impression materials include reversible (agar-agar), irreversible (alginate) hydrocolloids and synthetic elastomers (polysulfides, polyethers, silicones). Agar; b) Irreversible. (a) If the impression material is bonded to the tray, contraction occurs towards the tray. Fig. The key comparison between them is the amount and part of the tooth that they cover. i) Reversible (thermoplastic) E.g. A more widely used classification of materials involves consideration of the properties of the set material. (c) This results in an oversized die. This factor is primarily responsible for governing the principal applications of the materials. Mucostatic Impression technique. Impressions are the Key for a good prosthesis. Simos S. PMID: 29235338 [Indexed for MEDLINE] Publication Types: Case Reports; Comparative Study; MeSH terms. 780. denture prostheses. Requirements for impression material: Accurate & persise - mainly depend on viscosity of the mixed and the ability of the impression material to adapt closely to both the soft and the hard tissues. An inlay will incorporate the pits and fissures of a tooth, mainly encompassing the chewing surface between the cusps. Many criteria may be used to classify impression materials. The function of an impression material is to accurately record the dimensions of the … Impression is a negative replica of a mouth, same as film for a picture. Classification of materials according to viscosity is not, therefore as simple as it may seem. In addition to the requirements given above, there are two further requirements which apply specifically to materials used for recording undercuts. 16.4. Classification of impression materials: According to the elasticity of the materials. Start studying Chapter 46 Test Review. The newest class of impression material is the vinyl-polyether hybrids that include SENN (GC America, Alsip, IL; soon to be introduced in the U.S.). 16.1 Classification of impression materials by viscosity at a constant shear rate and temperature (23°C). When a substance behaves in this way, it is said to be pseudoplastic. Alginate; ii) Elastomeric impression materials The impression recorded with the elastic material accurately records the true shape of the tooth with the correct degree of undercut. Three Impression Material Classifications: A Comparison. Classification according to elastic properties and chemical type. They could be described as possessing rubbery characteristics. E. Classification of Impression Materials 1. a) reversible. For most materials, the dimensional change is a contraction and, providing the impression material is firmly attached to the impression tray, this produces an expansion of the impression ‘space’ and an oversized die, as illustrated in Fig. The thickest parts of the impression are compressed against the tray when they pass the widest part of the tooth crown. Prosthesis fabrication starts with an impression. This normally results in the formation of a ‘blow hole’ in the impression. For such products, a dry field of operation is essential. On being withdrawn from the patient’s mouth, which is typically at a temperature of 32–37°C, into the dental surgery, at a temperature of around 23°C, the impression undergoes approximately 10°C cooling. The tray is required because the materials are initially quite fluid and require support. The impression recorded with the viscoelastic material gives a distorted shape. 16.2 Impression materials. Since no pressure is applied, Tissue health is preserved.Hence, it is also known as Minimal pressure technique. 16.3 Diagram illustrating the effect of setting contraction. For greatest accuracy, the dimensional change should be minimal. The effect on the accuracy of fit of the resultant restoration depends on the type of restoration and the complexity of shape involved. Major 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. Impression techniques can be broadly classified into Muco static, Muco compressive, and selective pressure technique. Fig. The requirements of impression materials can be conveniently discussed under four main headings: In order to record the fine detail of the hard or soft oral tissues, the impression material should be fluid on insertion into the patient’s mouth. – As mentioned earlier, those that replace lost tooth structure and restore the function of the teeth mus t be strong and hard. E.g. – NUTRITION AND ORAL HEALTH. Based on material use A. Inelastic or rigid. (4) Additional factors such as cost, taste, colour etc. The accuracy of the model depends on the accuracy of the impression in which it was cast. Individual with deep undercuts, the material of choice for recording impression is alginate with perforated stock trays. I) Based on mode of setting & elasticity. A relatively fluid impression material confined in a close-fitting impression tray will compress the soft tissues to a greater extent than the same material used in a loosely-fitting tray. Hence impression materials are classified as being elastic or non-elastic. Fig. Impression materials is a group of auxiliary dental materials that is used in prosthodontics in the dentist’s everyday practice. The figures show the different test apparatus, instruments and components. Other materials are more compatible with moisture and saliva and no special precautions are necessary. Alginate; Polysulphide; Silicone; Polyether; Elastomers; Agar; 2. 16.3, the oversized die will result in a ‘loose-fitting’ crown. Precision impression making materials of lightly flowing consistency with ideal flow characteristics, maximum wetting power, and elastic resilience. Any substance or combination of substances used to record an impression or negative reproduction those are called as impression materials. This controls the thickness of the impression material and hence the pressure transmitted to the underlying tissues. impression waxes) and in other cases are very rigid but show little evidence of plastic deformation (e.g. A dental impression is an imprint of teeth and/or soft tissues, formed with specific types of impression materials that is used in different area of dentistry including Prosthodontics.. A correctly made dental impression will capture a part or all of a person's dentition and surrounding structures of oral cavity. By Dr. George Ghidrai. A ____ is a reproduction of someone's bite with the use of wax or elastromeric material. 16.5b) as well as the viscoelastic properties of the material itself. Inlays and onlays are used in molars or premolars, when the tooth has experienced too much damage to support a basic filling, but not so much damage that a crown is necessary. b) Elastic. The degree of distortion depends on the severity of the undercut, the thickness of the impression material and the time for which the impression is maintained in a compressed state (Fig. As we say, first impression should be good,likewise a dental impression recorded should cover all minute details of the mouth. If a material is rigid after setting it may not be possible to remove it from undercut areas. The behaviour of viscoelastic materials is described on p. 15–16, where the influence of time as an important parameter is discusse/>. It is of great importance, therefore, that inaccuracies are minimized at this stage, otherwise they will be carried through and possibly compounded later on. There are often significant variations between different brands of the same type of material and these variations can spread across the divisions between different levels of viscosity. The ‘setting’ of impression materials, whether it involves a chemical reaction or simply a physical change of state, generally results in a dimensional change which, naturally, affects accuracy. We need to understand which impression material and technique are used in an individual. The properties which are most important are rigidity and elasticity, since they determine whether an impression material can be used to record undercuts. Classification 1. Dental Impression Materials / classification Elasticity Elastomers / … watch our you tube video on dental pathshala to understand the classification of impression materials. Author R Giordano 2nd. Which of the following is not considered a classification of impression materials? However, silicones work best in a dry environment and may not be ideal if there is a lot of saliva. The impression stage is the first of many stages involved in the production of dentures, crowns, bridges, orthodontic appliances etc. Based on the degree of tissue Compression or the amount of pressure applied on the tissues. The accuracy of ‘fit’ and the functional efficiency of the appliance depends upon how well the model replicates the natural oral tissues. impression plasters). This … Learn vocabulary, terms, and more with flashcards, games, and other study tools. These materials must have adequate elastic properties and adequate tear resistance, coupled with a rigidity which is low enough to enable the impression to be removed. E.g. This new class of impression material combines properties from addition silicone and polyether impression materials. i) Hydrocolloid. – The chemical reaction invo lves chain lengthening, cross-linking, or both. Why wisdom tooth is called wisdom tooth? The effects of thermal changes are minimized if the values of coefficient of thermal expansion of the impression material and tray material are small. It should be remembered however, that viscosity often varies with the applied stress (p. 19). Dental Implantation, Endosseous/methods; Dental Implants; Dental Impression Materials/classification* Dental Impression Technique* Dental Prosthesis, Implant-Supported Many Dental Appliances Are Constructed Outside the Patient - Free download as Word Doc (.doc / .docx), PDF File (.pdf), Text File (.txt) or read online for free. Dental material However, the latter terms have been used for many years and are therefore likely to be familiar to dentists. impression compound; ii) Irreversible (thermosest) E.g. Other methods of classification are sometimes used and these may be based upon consideration of the properties of the materials either before or after setting. Impression plaster; Zinc oxide eugenol; Compound wax; B. Elastic. Classification by Use – Materials used to replace lost oral tissues are called r estorative materials. Most dentists are able to associate a material from a particular chemical group with a particular set of characteristics or properties which render it suitable for some applications but not for others. REVIEW OF DENTAL IMPRESSION MATERIALS R.G. The hydrophilic nature of the material allows it to be used in the. Hence, we have silicone materials, alginates, etc. The composition of the materials is … This standard replaces ISO/R 1563/1970 of which it constitutes a technical revision. Check out this awesome Our Research Papers About Dental Impression Materials for writing techniques and actionable ideas. Based on the degree of tissue Compression or the amount of pressure applied on the tissues. Punj et al. CRAIG Department of Biomaterials, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109 Adv Dent Res 2(l):51-64, August, 1988 ABSTRACT Major advances in impression materials and their application have occurred during the … Manufacturers of impression materials often supply tray adhesives which are used to enhance bonding. The way in which the material interacts with saliva is another factor affecting fine-detail reproduction. It is important that the impression material remains attached to the impression tray during the recording of the impression. Chemical Reaction or Physical Change – Impression mat erials set either by a chemical reaction or b y a physical change. To learn more about dentistry click on the link here, Impression Materials Classification with diagrams, Not eating can lose teeth? The fine detail recorded in an impression will only be transferred to the gypsum cast if there is adequate ‘wetting’ of the impression surface by the freshly mixed dental stone or plaster. After ‘setting’, the impression is removed from the patient’s mouth and the model cast using dental plaster or stone. This can result in blow holes and loss of fine detail. This requires a low viscosity or a degree of pseudoplasticity. Temporary. (b) During removal – the impression material is subjected to both compressive and tensile stresses. – Impression materials set by che mical reactions to form elastic rubber materials are called thermoset. 16.5 Diagram illustrating how an impression material is placed under stress during removal from an undercut area. Sep-Oct 2000;48(5):510-2, 514, 516. According to philips scienceof dental materials impression materials are classified on thebasis of setting and elasticity.Mode of setting rigid ElasticSet by chemicalreaction (irreversible)Impression plaster,zinc oxide eugenol.Alginate,polysulfide,polyether, silicone,Set by temperaturechange (reversible)Compound, waxes Agar hydrocolloid. Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), on 16 Impression Materials: Classification and Requirements, 30 Polycarboxylates, Glass Ionomers and Resin-modified Glass Ionomers for Luting and Lining. Impression techniques can be broadly classified into Muco static, Muco compressive, and selective pressure technique. As the name signifies Muco static means no pressure is applied On the tissues while taking Impression. Impression materials The materials which are used to take impression of natural teeth and their supporting tissue they are called as Impression materials. This obviously has a negative effect on the ability to achieve an adequate impression, but more seriously may undermine the viability of the remaining teeth as they may be subjected to a considerable stress if an attempt is made to remove the impression. Figure 16.2 lists the major groups of impression materials using the classification referred to above. As the impression is withdrawn it is likely that the material is also subjected to tensile stresses as the trapped material is stretched. Another complicating factor is the spacing of the impression tray. Materials which expand during setting result in undersized dies or casts. Impression materials that are used today can be classified according to their composition, mechanism of setting, mechanical properties, and applications. A low contact angle is favourable as it indicates good wetting. – Some restorative materials simulate the appearance of the tissues that are being replaced. Title: Impression materials (requirement and classification) 1 Impression materials (requirement and classification) Dr. Waseem Bahjat Mushtaha ; Specialized in prosthodontics; 2 Definition . Materials that very fluid are called mucostatic impression materials because they are less likely to compress soft tissues. SENN is supplied as a 2-paste automixing system and contains a polymer with polyether and siloxane (e.g., addition silicone) groups that will combine elements and benefits of both impression materials. wisdom tooth pain?. Classification of impression materials is the most frequently asked question for exams. When standing teeth are to be recorded, or when the patient has deep soft-tissue under-cuts, the set impression material must be flexible enough to be withdrawn past the undercuts and elastic enough to give recovery and an accurate impression. (a) Impression in place before removal. Receiving a qualitative impression is one of the main goals which the doctor faces at the prosthodontics treatment of patients with various diseases of a dento- For the simple crown preparation, illustrated in Fig. Thus, materials which are initially very fluid are often classified as mucostatic impression materials because they are less likely to compress soft tissues, whilst materials which are initially more viscous are classified as mucocompressive. 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