Tooth decay is caused by two kinds of bacteria​—“mutans streptococci and lactobacilli”—​that become a part of plaque, a sticky film of bacteria and food debris that forms on the teeth. Plaque bacteria feed on sugar and convert it into harmful acids that begin decay. Certain types of sugar are more easily turned into acids or are more likely to adhere to the teeth, giving the plaque more time to begin tooth decay.b Plaque that is not removed can harden into calculus, or tartar, around the gum line.

Controlling the plaque and especially the mutans streptococci bacteria is essential for preventing the spread of tooth decay. So if you want to preserve your smile, daily oral hygiene is a must. The Columbia University School of Dental and Oral Surgery states: “Combined with flossing, [brushing the teeth] is the single most important thing that you can do to maintain the health and vitality of your teeth and their supporting tissues.” Effective methods of brushing and flossing are illustrated on this and the following page. Your dentist may recommend other tools and techniques that will help you to clean your teeth effectively and thus protect your smile.

Dentists are being trained more and more to implement preventive measures in order to reduce the damage from demineralization. By treating lesions when they are small, many times the decay process can be reversed. Thus, by focusing on early detection and treatment, your visit to a dental health care professional need not be an unpleasant experience.

However, if the acid created by plaque remains on the teeth, caries, or decay, will result. If the decay is not stopped, a cavity may develop. The tooth then needs attention. When decay has not yet reached the pulp, the tooth’s nerve supply, the tooth is usually restored with a filling.

The dentist uses a drill to clean the cavity and to shape the opening for a filling. Then the filling material is inserted into the opening. Amalgam fillings harden quickly and are carved to shape, while composite resins are cured using a blue fiber-optic light. If cavities are left untreated and decay spreads to the pulp of the tooth, root-canal therapy or even tooth removal may become necessary.