Cavities, which dentists sometimes call dental caries, are spots of tooth decay. They can range in size from tiny to large enough to break teeth.

In 2011–2012, 91% of adults in the United States had cavities, yet many did not know it. This is because cavities do not typically hurt until they get deep enough into the tooth to affect the nerve below.

Cavity pain can range from mild to unbearable. When a cavity eats away at the enamel of a tooth, a person might find that it is more sensitive, especially when brushing the teeth or drinking hot or cold beverages.

Cavities that cause deeper damage in the tooth can affect the nerve, causing intense pain.

Sometimes, cavities can grow so large that bacteria can get into the gums, or even the bone underneath the teeth. This can cause intense, unrelenting pain, as well as serious infections.

Sometimes, an abscessed tooth stops hurting for a period of time when the infection kills the nerve or the pulp of the tooth.

However, a person may still have other symptoms, such as swelling, and the pain may return if the infection reaches the gums or bone.

Bacteria that eat sugar live on the teeth. A person is likely to have more bacteria in their mouth when they eat a very sugary diet, do not brush their teeth, or do not seek regular dental care.

Over time, these bacteria can eat into the enamel of the teeth, eventually causing decay deep in the tooth.

These bacteria form biofilms that cause plaque, making them more difficult to remove. Over time, the bacteria damage the sensitive pulp and nerve of the tooth, causing cavity pain.

Many factors can influence a person’s susceptibility to cavities, including their individual microbiome. The microbiome is a person’s unique colony of bacteria and other microoranisms that can either help or hinder the growth of harmful bacteria in the mouth.

Research also suggests that the bacteria that cause cavities are contagious. A person can transmit cavity-causing bacteria to another person by kissing them, sharing food or drinks with them, or sneezing on or near them.