Even with diligent brushing some spots between the teeth can be missed, and even the most attentive flossing won’t clean all the plaque that hides beneath the gum line. When plaque bacteria is missed in hard-to-reach places, it hardens into tartar which can only be removed by a professional oral hygienist. A buildup of plaque and tartar left untreated can lead to more serious oral health problems such as tooth decay and gum disease.