The most common cause of a toothache is tooth decay, although toothache may not be present in the early stages of decay. Other causes of a toothache might include:

• An infection of the tooth (abscess). A red, swollen, painful bump may be found near or on the side of the sore tooth. The tooth may especially hurt when you bite down.
• An impacted tooth. Gums may be red, swollen, and sore. The area around this tooth can ache, throb, and be quite painful.
• Problems with or injury to the pulp.

A toothache can also be caused by another health problem, such as:

• An early sign of a heart attack.
• A sinus infection.
• Vitamin deficiencies, such as too little vitamin B12.
• Facial shingles.
• Cluster headaches.
• Nerve-related disease, such as trigeminal neuralgia.
• Diseases such as diabetes or alcoholism.
• Illegal drug abuse, such as methamphetamines.