Bacteria create a biofilm known as plaque to help stay attached to the tooth. If this biofilm is not removed through proper brushing and flossing, it becomes a hard substance known as tartar or calculus. Calculus needs to be removed by your dental hygenist because it causes a great deal of inflammation in your gums- the foundation of support for your teeth. Active inflammation leads first to gingivitis and then, if left long term, to periodontitis- a disease involving loss of bone around your teeth which can cause them to become loose. Any area of active inflammation in the body is not good for your overall health and can negatively affect the stability of other health conditions you may have.