The bacteria in tooth plaque are free to release acids that damage tooth enamel. Regular acid assaults on enamel can wear holes in teeth, commonly called cavities. If left alone, plaque build-up gradually hardens, creating tartar or calculus on your teeth. Tartar is petrified plaque. Once it’s there, you need the help of a dentist or dental hygienist - tartar cannot be brushed off. Tartar above the gum line also contributes to gingivitis, or gum disease.