When bacterial plaque is not removed on teeth, it can combine with other substances and may calcify into a rough, porous deposit called tartar or calculus. The removal of plaque and bacteria can be more difficult when tartar already accumulates on the teeth's surface and below the gums. Unlike plaque that can be removed by constant and proper brushing and flossing, only a dental hygienist can remove tartar or calculus. Once bacterial plaque and tartar are not eradicated, gum irritation and gum infection can arise causing damage to gums, bones and other connective tissues that supports the teeth. With these condition, teeth can eventually become mobile, may fall out or may have to be removed. Complex treatments may be required at this stage to prevent tooth loss.