What is black calculus?

According to this page on gums and gum disease from Britain.TV: "A principal cause of gum disease is calculus. This is the hard, chalky material that forms when soft plaque is left in place by inadequate brushing and flossing. Visible calculus is yellow or white, but black calculus also forms underneath the gums. Once started, the process encourages further plaque to form, and the amount and thickness of the calculus steadily increases." This page also lists a few more tidbits of information about causes and treatment. (It mentions "dental scaling" to treat calculus.) More opinions from FAQ Farmers: * Besides the definition of calculus already stated, calculus can turn black due to blood. Gingivitis and other Periodontal diseases cause inflammation and there is essentially ulceration of the tissue below the gum line, which can bleed when irritated. Bleeding is usually induced by brushing and flossing in an unhealthy mouth. Tartar can become dark when it is stained with blood. This usually happens when someone has gum disease, and tartar stays bellow the gum and get stained with blood.

If someone has black calculus, they should consider removing it with a dental cleaning or scaling at a dental office.