| hydrocolloid | A gelatinous colloid in unstable equilibrium with its contained water, useful in dentistry for impressions because of its dimensional stability under controlled conditions. (05 Mar 2000) |
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| reversible hydrocolloid | A hydrocolloid composed of a base substance whose physical state may be changed to that of a liquid by the application of heat and then changed to that of an elastic gel by cooling. (05 Mar 2000) |
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| irreversible hydrocolloid | A hydrocolloid whose physical state is changed by an irreversible chemical reaction when water is added to a powder and an insoluble substance is formed. (05 Mar 2000) |