Impression materials can be classified based on their properties and composition. The main classifications of impression materials are as follows:
Based on setting mechanism:
a. Chemical-curing impression materials: These materials set by a chemical reaction, such as the polymerization of a monomer to form a polymer.
b. Physical-curing impression materials: These materials set by physical changes, such as cooling or evaporation of a solvent.
Based on physical state:
a. Hydrocolloid impression materials: These materials are hydrophilic and set by gelation of a colloid in water, such as alginate.
b. Non-hydrocolloid impression materials: These materials do not rely on gelation of a colloid and may include elastomers, silicones, or metal impression compounds.
Based on flexibility:
a. Rigid impression materials: These materials have low flexibility and are used for capturing fine details in the impression.
b. Flexible impression materials: These materials have higher flexibility and can be used in areas with undercuts or irregularities.
Based on composition:
a. Alginate impression materials: These materials are made from calcium alginate, a natural polysaccharide derived from seaweed.
b. Silicone impression materials: These materials are made from silicone polymers and are known for their dimensional stability and tear resistance.
c. Polyether impression materials: These materials are made from polyether polymers and are known for their accuracy and high detail reproduction.
d. Impression compounds: These materials are typically made from waxes and resins and are used at higher temperatures for preliminary impressions.
It is important to select the appropriate impression material based on the specific requirements of the clinical situation, such as accuracy, detail reproduction, dimensional stability, compatibility with gypsum products, and patient comfort.
