In dentistry, calculus or tartar refers to hardened plaque on the teeth, formed by aging in the presence of saliva, debris[?], and minerals. Its rough surface provides an ideal medium for bacterial growth, threatening the health of the gums[?] and absorbing unaesthetic stains far more easily than natural teeth.
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... Maritime Province in East Siberia, Russia. The European names derived from misinterpretation of a Manchu name "sahaliyan ula angga hada" (peak of the mouth of Amur ...