| (FGDP) Diploma Restorative Dentistry
TITLE OF ASSIGNMENT
| Discuss the range of impression materials available for use in fixed and removable prosthodontics and indicate where you might use each material.
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Discuss the range of impression materials available for use in fixed and removable prosthodontics and indicate where you might use each material.
To provide a current and relevant report of impression materials available to clinicians. A sound knowledge is imperative to achieve an accurate replica of intra-oral structures and good quality fixed and removable prosthesis.
Impression material can be classified as elastic or ridged. The ridged impression materials cannot engage undercuts that may present on teeth or bone. Consequently their use is restricted to edentulous patients. An example of this is impression compounds which softens at 60°C.
Elastic materials are subdivided in to hydrocolloid and elastomeric. Hydrocolloid impression materials include:
* agar, a reversible hydrocolloid (although does give good surface detail, requires a water bath, slow setting times, hence not used commonly these days) * alginate, which is irreversible and very commonly used. The elastomeric materials are:
* polysulphide, the very fits type of material, this is now deemed ‘old fashioned and rarely used due to demanding technique, unpleasant smell and possible toxicity of lead dioxide ingredient. * Polyether
* Silicone (condensation-cured)
* Silicone (addition-cured)
Desirable properties of impression materials:
Accurate reproduction of surface detail: requires a low viscosity material allowing it to adapt closely to the hard and soft tissues. Hydrophillic...
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