That sticky, invisible biofilm (a colony of microorganisms)
that forms daily on your teeth is
called plaque. If it's allowed to, harden, it's called tartar or calculus. Plaque contains bacteria, which turn sugars and
starches from food into an acid that causes tooth demineralization (dissolving
of the enamel) and leads to tooth decay (cavities, or caries). Calculus
irritates the gums, which brings about gingivitis (inflammation); if left untreated, this can develop
into the more serious periodontal disease.The bacteria that live in the human mouth are not normally harmful, but if they are not removed by brushing, they can build up into a thin layer. Then the bacteria nearest the tooth surface begin to metabolize food with anaerobic respiration (without oxygen); the waste ducts of that process are very acidic.
Daily brushing, flossing, and use of mouthwash are the primary preventative methods. Dentists can remove plaque in a process called scaling, if gum disease is present, root planting is utilized. (All Facts Considered, by Kee Malesky)