The final set structure consists of ZnO particles embedded in the matrix of zinc eugenolate. The second stage is a typical acid-base reaction in which zinc hydroxide reacts with eugenolic acid to form zinc eugenolate, forming a chelate and water as a byproduct. It sets in two steps: first, by the hydrolysis of ZnO to form zinc hydroxide (water is required to initiate the reaction).

Manipulation: equal lengths are squeezed out from both tubes on a paper pad or a glass slab and mixed with a broad end spatula until mixed to an even color. Instruments and armamentarium: paper pad or glass slab and broad end spatula. *Noneugenol pastes (for patients who are allergic to eugenol) contain carboxylic acids. The type 2 impression compound is used to make an impression tray to make a wash impression.įillers 20%, resinous balsam 10%, accelerator, color pigments 5% The type 1 stick impression compound is softened over a flame and placed on the borders of the custom impression tray. These impressions must be corrected with a second impression made in a custom impression tray fabricated on the primary cast of the patient. The impression compound is a mucocompressive material, meaning that it impresses the mucosa when subjected to compression. The water bath temperature is kept at around 55-60 degrees Celsius, above the impression compound's fusion temperature. Type 1 sheet impression compound is softened in a water bath with warm water and is placed in a stock tray to copy edentulous ridges. Instruments and armamentarium: water bath, gauge piece, burner, scalpel handle, and blade to modify the impression. It is a thermoplastic material that sets by physical reaction only. However, there is always a scope for new impression materials, as no impression material is 100% accurate until the date. With the advancement in technology, digital dentistry is also making its way into the field. First came polysulfide, then condensation silicone followed by polyether, and then addition silicones. When the algae used to manufacture agar was unavailable during the second world war, Americans used local algae to manufacture another elastic impression material known as alginate, which has gained popularity since then.Īlginate and agar have disadvantages, like dimensional instability and low tear strength, which led to the manufacture of elastomeric (also known as rubber-based) impression materials. Although this jelly-like material was elastic, it required a complicated procedure to be used as an impression material. That is when agar, a reversible hydrocolloid manufactured from algae, was introduced in dentistry. Thus, there was always a need for an impression material that could remain elastic even after setting. All the impression materials used until that date became rigid after setting and could not copy the oral tissues accurately. Still, the problem with this material was that it was rigid and could not reproduce undercut areas. Then in 1857, Charles Stent created a thermoplastic modeling compound similar to today's impression compound. Wax was the only impression material used in dentistry until the mid-19th century when gutta-percha first appeared.

The final restoration or prosthesis fit depends on how accurately the impression material has recorded the tissue details. Particular treatment, such as removable and fixed prostheses, can be executed thanks to dental casts. This procedure provides a tridimensional and accurate mouth replica, allowing dental work even in the absence of the patient.ĭental models enable dentists to perform a better diagnosis and treatment planning since the teeth can be meticulously visualized and studied from angles that are difficult to see in the patient's mouth. e.g.Impression materials are used to copy the teeth and surrounding oral structures by creating a dental impression poured with dental plaster to fabricate a dental cast.IV) Based on the amount of pressure applied Impression compound, zoe impression paste, alginate, Elastomers ZOE impression paste, Elastomers for CDĪ) Edentulous- For complete denture prosthesis Impression compound, Impression plaster, Alginate II) Based on type of impression & area of use Polysulfides Polyether, Addition silicones, Condensation silicones Zoe impression paste, Impression plaster. Definition: It is the negative replica of the structures of the oral cavity be it hard(tooth) or soft(gingiva, mucous membrane) structures, which are used to fabricate the cast or model of the patient, and for making crowns, dentures, and other prosthesis.

Dental impression meaning