Toothache (cont.)

The most common cause of a toothache is a dental cavity. Dental cavities (caries) are holes in the two outer layers of a tooth called the enamel and the dentin. The enamel is the outermost white hard surface and the dentin is the yellow layer just beneath the enamel. Both layers serve to protect the inner living tooth tissue called the pulp, where blood vessels and nerves reside. Bacteria in the mouth convert sugar into acid. The acid softens and dissolves the enamel and dentin, creating cavities.

Small, shallow cavities may not cause pain and may go unnoticed. The larger deeper cavities can be painful and collect food debris. The inner living pulp of the affected tooth can become irritated by bacterial toxins or by foods and liquids that are cold, hot, sour, or sweet, thereby causing severe toothaches. Severe injury to the pulp can lead to the death of pulp tissue, resulting in a tooth infection (dental abscess). Deeper cavities can also lead to a small swelling or a "gum blister" which forms near the affected tooth. Toothaches from these larger cavities are the most common reason for visits to dentists.

Treatment for cavities depends on the severity. For a small and shallow cavity, treatment usually involves a dental filling. For a larger cavity, a filling may be insufficient, resulting in the need for an onlay or crown. For a cavity that has penetrated and injured the pulp or for an infected tooth, a root canal procedure of the affected tooth is typically required. In a few instances, an extraction may be unavoidable depending on the size of the infection. The root canal procedure involves removing the dying pulp tissue (thus avoiding or removing the tooth infection) and replacing it with an inert filling material. The procedure is used in an attempt to save the dying tooth from extraction. Once a root canal procedure is completed, the tooth is more prone to fracture and will oftentimes require a crown to protect it.

Sometimes, a dental abscess can be the cause of rapid swelling in the mouth that could potentially spread to nearby parts of the face such as the sinuses, the floor of the mouth, or the bloodstream. This rapid swelling is caused by the spread of infection and can be an emergency if the spreading cannot be controlled and results in a compromised airway or more serious condition. Treatment at a hospital emergency room may be necessary.

Source: MedicineNet.com
http://www.medicinenet.com/toothache/article.htm