Tooth brushing is the act of scrubbing teeth with a toothbrush equipped with toothpaste. Since only two thirds of the outer tooth can be reached by a toothbrush, interdental cleaning (with floss or an interdental brush) can usefully accompany tooth brushing. Together, these two activities are the primary means of cleaning teeth, one of the main aspects of oral hygiene. Brushing teeth properly helps prevent cavities, and periodontal, or gum disease, which causes at least one-third of adult tooth loss. If teeth are not brushed correctly and frequently, it could lead to the calcification of saliva minerals, forming tartar.