A toothache is a pain felt in a person's tooth, normally when the tooth is hurt. A tooth can be hurt by tooth decay caused by plaque or by an injury.

Toothache may be caused by dental (odontogenic) conditions (such as those involving the dentin-pulp complex or periodontium), or by non-dental (non-odontogenic) conditions (such as maxillary sinusitis or angina pectoris). There are many possible non-dental causes, but the vast majority of toothache is dental in origin.

Since most toothache is the result of plaque-related diseases, such as tooth decay and periodontal disease, the majority of cases could be prevented by avoidance of a cariogenic diet and maintenance of good oral hygiene. A cariogenic diet is one high in frequent consumption of refined sugars. Good oral hygiene includes brushing the teeth twice a day with fluoride toothpaste and flossing. Regular visits to a dentist for checkups also increases the likelihood that problems are detected early and averted before toothache occurs.

There are many causes of toothache and its diagnosis is a specialist topic, meaning that attendance at a dentist is usually required. Since many cases of toothache are inflammatory in nature, over the counter non-steroidal anti-inflammatory drugs (NSAIDs) may help (unless contraindicated, such as with a peptic ulcer). Generally, NSAIDs are as effective as aspirin alone or in combination with codeine.

However, simple analgesics may have little effect on some causes of toothache, and the severe pain can drive individuals to exceed the maximum dose. For example, when acetaminophen (paracetamol) is taken for toothache, an accidental overdose is more likely to occur when compared to people who are taking acetaminophen for other reasons.

Another risk in persons with toothache is a painful chemical burn of the oral mucosa caused by holding a caustic substance such as aspirin tablets and toothache remedies containing eugenol (such as clove oil) against the gum. Although the logic of placing a tablet against the painful tooth is understandable, an aspirin tablet needs to be swallowed to have any pain-killing effect. Caustic toothache remedies require careful application to the tooth only, without coming into excessive contact with the soft tissues of the mouth.

For the dentist, the goal of treatment generally is to relieve the pain, and wherever possible to preserve or restore function. The treatment depends on the cause of the toothache, and frequently a clinical decision regarding the current state and long-term prognosis of the affected tooth, as well as the individual's wishes and ability to cope with dental treatment, will influence the treatment choice.

Often, administration of an intra-oral local anesthetic such as lidocaine and epinephrine is indicated in order to carry out pain-free treatment. Treatment may range from simple advice, removal of dental decay with a dental drill and subsequent placement of a filling, to root canal treatment, tooth extraction, or debridement.