3-13. REQUIREMENTS FOR IMPRESSION MATERIAL
a. General. An impression material must meet a wide range of requirements in order to provide an accurate impression of the different tissues.
b. List of Requirements. The following are some of the more important requirements.
(1) The material should flow or be pliable at a temperature that will not injure the oral tissue.
(2) It should set quickly, preferably within 2 to 4 minutes, at body temperature.
(3) It should unite into a solid mass without adhering to the oral tissues or to the material used for the cast.
(4) It should fall into all irregularities and fine lines in the area to reproduce without displacing soft tissue.
(5) It must retain an accurate reproduction of surface detail when it solidifies and is withdrawn from the mouth.
(6) It must have dimensional stability. It must not expand, contract, or become deformed in any way because of temperature changes, atmospheric conditions, or the pouring of the cast.
(7) It must not be too unpleasant to the patient.
(8) It must not flake (after solidifying) when trimmed with a sharp knife at room temperature.