Plaque contains bacteria that cause cavities and gum disease. As plaque forms and is not removed by proper brushing and flossing, it can harden into tartar — sometimes called calculus — which is calcified (or hardened) plaque that attaches to the enamel on your teeth, as well as below the gum line.
Our mouths are full of bacteria. These bacteria, along with mucus and other particles, constantly form a sticky, colorless “plaque” on teeth. Brushing and flossing help get rid of plaque. Plaque that is not removed can harden and form “tartar” that brushing doesn’t clean. Only a professional cleaning by a dentist or dental hygienist can remove tartar.