![]() ![]() ![]() for study models, for partly edentulous patients, for orthodontic devices and for models of antagonist arches. They are used for taking various types of impression, e.g. Setting times vary, depending on the type of alginate. Irreversible hydrocolloids or alginates come in the form of a powder to be mixed with water.Īlginates are very widely used given their ease of working, low cost, good precision and elasticity. They are still used in dental laboratories for model duplication purposes, however. Over the years, the reversible nature of these materials and the need for heating equipment and special impression trays with built-in water cooling circuits to set the materials in the mouth have led to dental practices abandoning them. They are termed ‘reversible’ because they can be softened by heating until they flow into any shape. They had to be heated to liquefaction temperature prior to use. Reversible hydrocolloids were once commonly used as impression materials. Let us look in greater detail at the characteristics, applications and potential disadvantages of all these types of material. Depending on their chemical composition, elastomers can be divided into the following types: polysulfides, condensation silicones (C-silicones), addition silicones (A-silicones) and polyethers. Elastomers – These are materials that demonstrate a similar elastic behaviour to natural rubber.Hydrocolloids – These include reversible hydrocolloids like agar agar and irreversible hydrocolloids like alginates.Elastic impression materialsĮlastic impression materials can be divided into the following types: ![]() Rigid (or non-elastic) impression materialsĪll impression materials fall into one or the other of these categories, which differ in how they can be used after setting in the oral cavity.Įlastic impression materials are by far the most commonly used, but rigid materials are to be preferred in certain clinical cases and may also be used in conjunction with elastic ones for certain applications.Impression materials can be divided into two main types : What impression materials are used in dentistry and how are they classified? ![]()
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