What are tartar?

Hardened plaque: Plaque forms around your teeth all the time. If not removed it gets hardened by the minerals in your saliva. Once it has turned into tarter it is much more difficult to remove. It also becomes a surface for further plaque forms. This threatens the health of your gums.

Calcified plaque: Tarter, or calculus, is a hard substance that adheres to the outer covering of a tooth. It is the result of bacterial plaque that has accumulated on a tooth and lasted long enough to calcify.