Dental Caries


What Is It?

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 build up on the teeth (along with saliva, bits of food and other natural substances) in a sticky film called plaque. Plaque forms especially easily in certain places. These include:

  • Cracks, pits or grooves in the back teeth
  • Between teeth
  • Around dental fillings or bridgework
  • 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. This erodes the enamel or creates pits in it that are too small too see at first. But they get larger over time. The damage can occur anywhere the tooth is exposed to plaque and acid. This includes the hard outer enamel on the tooth crown or parts of the root that have been exposed because of receding gums. Once decay penetrates the protective enamel, it can enter the softer, vulnerable dentin. This is the main body of the tooth. A cavity can even penetrate the soft tooth pulp and the sensitive nerve fibers within it. No one really knows what causes the pain people get with cavities. Theories include:

  • Inflammation caused by bacteria
  • Exposure of the root surface
  • Imbalance of fluid levels in tiny openings called 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.This will be part of the exam, whether it is a routine visit or an appointment made because of pain. The dentist will look at the teeth and will probe them with a tool called an explorer to look for pits or areas of damage. X-rays will be taken on a set schedule, or if the dentist suspects hidden caries.

Expected Duration

How long caries lasts is determined by the stage at which it is found. White spots may indicate early caries that has not yet eroded through the enamel. Early caries may be reversed if acid damage is stopped and the tooth is given a chance to repair the damage naturally. Caries that has destroyed enamel cannot be reversed. Most caries will continue to get worse and deeper. With time, the tooth may decay down to the root. The amount of time the erosion takes will vary from person to person. Caries can erode to a painful level within months or years.


You can prevent cavities by reducing the amount of plaque and bacteria in your mouth. The best way to do this is by daily brushing and flossing daily and getting professional dental cleanings twice a year. You also can reduce the amount of acid in your mouth by eating sugary or starchy foods less often during the day. Your mouth will remain acidic for several hours after eating, so snacking 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 adults, molars can be protected with sealants. In children, both baby molars and permanent molars can be sealed. Dentists also can use sealants on molars that have early signs of tooth decay, as long as the decay has not broken through the enamel.


The standard treatment for a cavity is to fill the tooth. First, the dentist will numb the area. Then the decayed material in the cavity is removed and the cavity is filled. Fillings usually are made of dental amalgam or composite resin. Amalgam is a silver-gray material made from silver alloyed with copper or other metals to make it more durable. Composite resin offers a better appearance because it is tooth-colored. 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, 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 part of the tooth you can see remains relatively intact, but there is damage inside 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.

When To Call A Professional

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 drinks, contact your dentist.


If a cavity is not treated, it likely will cause the tooth to erode significantly. Eventually, the tooth may be destroyed by uncontrolled decay. Having caries increases your risk of more caries for several reasons:

  • The same oral care and dietary habits that led to the erosion of teeth by plaque and acids may cause more decay.
  • Bacteria tend to stick to fillings and other restorations more than to smooth teeth, so those areas will be more likely to have new caries.
  • Cracks or gaps in the fillings may allow bacteria and food to enter the tooth, leading to decay from beneath the filling.