A gelatinous colloid in unstable equilibrium with its contained water, useful in dentistry for impressions because of its dimensional stability under controlled conditions.
- irreversible h. a h. whose physical state is changed by an irreversible chemical reaction when water is added to a powder and an insoluble substance is formed.
- reversible h. a h. composed of a base substance whose physical state may be changed from a solid or semisolid to a liquid by the application of heat and then changed to that of an elastic gel by cooling.
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hy·dro·col·loid -'käl-.ȯid n any of several substances that yield gels with water (as alginic acid salts, agar, carrageenan, and related polysaccharide gums) and that are used esp. as protective colloids and as impression materials in dentistry
hy·dro·col·loi·dal -kə-'lȯid-əl, -kä- adj
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hy·dro·col·loid (hi″dro-kolґoid) [hydro- + colloid] a colloid system in which water is the dispersion medium.Medical dictionary. 2011.