Impression materials

Any substance or combination of substances used to record an impression or negative reproduction those are called as impression materials.

Impression technique

A method and manner used in making a negative likeness.

Classification

1. Based on material use

A. Inelastic or rigid

• Impression plaster
• Zinc oxide eugenol
• Compound wax

B. Elastic

• • Alginate

• • Polysulphide

• • Silicone

• • Polyether

• • Elastomers

• Agar

2. Based on setting of materials

A. Chemical reaction

• POP
• ZnOE
• Alginate
• Silicone

B. Physical change

• Agar-agar

3. Based on viscosity

A. Mucostatic

• Impression plaster
• Agar
• Light body elastomer

B. Mucosuppressive

• Impression compound
• Alginate

C. Pseudo-plastic

• Addition silicone

4. Based on interaction with water

A. Hydrophobic

• Polysulphide
• Addition silicone

B. Hydrophilic

• Putty impression plaster

5. Based on use

A. Primary impression materials

• Impression compound
• Alginate

B. Secondary impression materials

• ZnOE
• Medium body elastomers

C. Duplicating materials

• Agar

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