1. Increase by addition to the periphery of material of the same nature as that already present; e.g., the manner of growth of crystals. SYN: accrementition (2). 2. In dentistry, foreign material (usually plaque or calculus) collecting on the surface of a tooth or in a cavity. 3. A growing together. [L. accretio, fr. ad, to, + crescere, to grow]
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ac·cre·tion ə-'krē-shən n the process of growth or enlargement esp increase by external addition or accumulation (as by adhesion of external parts or particles) compare APPOSITION (1), INTUSSUSCEPTION (2)
ac·cre·tion·ary -shə-.ner-ē adj
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ac·cre·tion (ə-kreґshən) [L. ad- to + crescere to grow] 1. growth by addition of material. 2. accumulation. 3. adherence of parts normally separated.Medical dictionary. 2011.