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Dental caries is the medical term for tooth decay or cavities. It is caused by acid erosion of tooth enamel. Many different types of bacteria normally live in the human mouth. They accumulate (along with saliva, food particles and other natural substances) on the surface of the teeth in a sticky film called plaque.

Plaque forms especially easily in cracks, pits or fissures in the back teeth; between teeth; around dental fillings or bridgework; and near the gum line. Some of the plaque bacteria convert sugar and carbohydrates (starches) in the foods we eat into acids. These acids dissolve minerals in the surface of the tooth, forming microscopic pits or erosions that get larger over time.

The damage can occur anywhere the tooth is exposed to plaque and acid, including the hard outer enamel on the tooth crown or the unprotected root of the tooth that has been exposed by gum recession. Caries can penetrate the protective enamel down to the softer, vulnerable dentin (main body of the tooth) and continue through to the soft tooth pulp and the sensitive nerve fibers within it. No one really knows what causes the pain associated with cavities, but theories include inflammation caused by bacteria, exposure of the root surface and an imbalance of fluid levels in the tubules inside the dentin.


Early caries may not have any symptoms. Later, when the decay has eaten through the enamel, the teeth may be sensitive to sweet foods or to hot and cold temperatures.


A dentist will look for caries at each office visit, regardless of whether it is a routine visit or an appointment made by the patient because of pain. The dentist will examine the teeth visually and will probe the teeth with an instrument called an explorer to determine if there are pits or areas of damage. Periodically, or if the dentist suspects hidden caries, X-rays will be taken by looking at the teeth.


Cavities can be prevented by reducing the amount of plaque and bacteria in the mouth. The best way to do this is by daily brushing and flossing and professional dental cleanings twice a year. You also can reduce the amount of acid in your mouth by eating sugary or starchy foods less frequently during the day. Your mouth will remain acidic for several hours after eating, so snacking throughout the day is more likely to lead to caries than avoiding between-meal snacks. Chewing gum that contains xylitol helps to counteract the acidity that occurs after eating.

Teeth can be strengthened by fluoride. A dentist can evaluate your risk of caries and then suggest appropriate fluoride treatments. In children, new molars can be protected by having the dentist apply a sealant as soon as the teeth come fully into the mouth.


The standard treatment for caries is to fill the tooth. After the dentist removes the decayed material in the cavity (usually following the use of anesthesia to block the pain), the cavity is filled. Fillings usually are made of a dental amalgam, which is a silver-gray material made from silver alloyed with copper or other metals in order to improve durability, or of a composite resin, which is tooth-colored for a better appearance. Amalgams are used primarily in molars and premolars. Resins are used primarily in the front teeth, although it is possible to use them in all teeth. Gold inlay may be used if greater strength is needed, but this is more expensive.

If a cavity is large with extensive erosion, the remaining tooth may not be able to support the amount of filling material that would be needed to repair it. In this case, the dentist will remove the decay, fill the cavity, and cover the tooth with an artificial crown.

Sometimes the crown of the tooth remains relatively intact, and there is more damage in the interior of the tooth. In these cases, the dentist may refer you to a dental specialist called an an endodontist for root canal treatment. In this procedure, the endodontist removes the tooth's pulp and replaces it with an inert material. In most cases, the tooth's natural crown will need to be replaced with an artificial crown.

The early stages of decay are usually painless. Only regular professional examinations and X-rays can detect early trouble. If you develop sensitivity to chewing or to hot, cold or sweet foods or beverages, contact your dentist.