Most toothaches are caused by injury to the dental pulp, commonly referred to as the "nerve" in the tooth. Mild toothaches occur in each of us at some point in our lives, but normally will subside with time, as the pulp heals. They can be caused by tooth decay or trauma to the tooth, but often are "idiopathic", meaning they have no known cause. (Less commonly wisdom teeth or other teeth may cause pain unrelated to the nerve in the tooth, but this is usually caused by periodontal infection, i.e. infection of the gums and surrounding bone of a tooth.)
Toothaches usually start out as mild sensitivity, usually only to cold, then progress to sensitivity to heat, after which the tooth often hurts without any provocation, and may progress to excruciating pain. (Reputedly, the two worst sources of pain in humans are toothache and renal colic (passing kidney stones)). Intense pain is an indication of severe inflammation in the dental pulp, and eventually results in necrosis, or death of the pulp (i.e. nerve).
In rare instances, pulpal necrosis may occur in the absence of symptoms, however is almost always later accompanied by sensitivity to biting and chewing. In contrast to the earlier symptoms of hot/cold sensitivity, this pain is the result of inflammation in the bone at the tip of the root of the tooth where the nerve enters. Once the pulp in the tooth has died, however, the tooth itself can feel no pain. Instead, the pain is actually eminating from pressure in the bony socket around the root of the tooth, hence the sensitivity to biting. This is why many toothaches seem to sponataneously dissappear, only to reappear at a later date, once bone inflammationwhich is secondary to pulpal necrosis is present. Usually the inflammation in the bone is a reaction to bacterial infection of the dead pulpal tissue, and typically progresses in severity to become an abscess.
An acute abscess is characterized by severe pain, which is worsened by biting or tapping the affected tooth.
A chronic abscess is usually characterized by slight to moderate pain, but with the presence of a "gum boil" located in the gum near the root tip of the affected tooth. A chronic abscess will typically follow an acute abscess, once a drainage route, called a fistula, has formed. This allows drainage of pus from the abscess. The severe pain subsides because the pressure is relieved.
It is important that any abscesses be treated, as they can progress to life-threatening illnesses.
Assessment of Toothaches
Mild toothaches and/or sensitivity often disappear over time without any treatment. In fact, most sensitivity to cold is actually caused by gum recession and not any injury to the pulp.
The roots of teeth do not have the dense, protective layer of enamel over their surfaces. Thus, if the gums recede past the point at which the enamel ends, the highly sensitive bare root surface will become exposed in the mouth, at times causing great sensitivity of short duration especially to cold liquids. This type of sensitivity also often presents as pain when scraping a fingernail along the gumline of a tooth. Fortunately, root sensitivity usually gets better with time, sometimes aided by the use of a sensitivity toothpaste. (Gum recession, however, is not considered a normal process, and if progressive in nature, usually is a sign of periodontal disease.)
Sensitivity in a tooth to sweets often indicates a deep cavity in the tooth, or leaky filling. This can usually be corrected simply by placing a new filling in the tooth.
If there is tooth sensitivity that lingers well beyond the point of stimulus (e.g. cold), exquisite sensitivity to heat, or spontaneous pain, this is strongly suggestive of irreversible inflammation of the dental pulp, or "nerve." In other words, the nerve is probably dying, and cannot repair itself. This condition of "irreversible pulpitis" can usually be detected before the severe pain sets in, and therefore best treated early if the diagnosis is very clear.
Treatment of Toothaches
There are only two treatment options available to alleviate pain caused by inflammation or necrosis of the dental pulp.
First, but usually less favorable, is removal of the tooth. This option is normally reserved for situations in which the tooth is not functional or capable of being restored to function. This is often the case with the wisdom teeth.
The second option, and by far more common, is root canal therapy. Contrary to popular myth, root canal treatment is rarely painful. Rather, it relieves the pain in the tooth. Many recent advancements in this field have made this a relatively simple, atraumatic procedure. In contrast to even the recent past, most root canal treatments can now be performed completely in a single appointment, usually with no or only mild post-operative discomfort.
What is Root Canal Therapy?
Root canal therapy, or endodontic treatment, involves removing the dental pulp from the canal or canals which run the length of the respective roots of each tooth. The procedure is performed under local anesthetic through a small hole made in the top of the tooth in back teeth, or in the back of the tooth for front teeth. After the pulp has been removed, the canals are carefully cleaned and sterilized, and then are filled with a biologically inert substance called gutta percha, which seals off the canals to prevent bacterial infiltration.
In cases where an acute abscess is present, and the pulp is necrotic (i.e. dead), the infection can usually be drained through the small hole made in the top of the tooth, which relieves the pressure and pain. Once the infection has been cleared up with the aid of antibiotics, the treatment can then be completed.
It is important to recognize that even though the "nerve" in the tooth may no longer exist, a tooth will still be able to function normally. However, endodontically treated teeth tend to have more brittle and weaker tooth structure than vital (live pulp) teeth. It is for this reason that it is almost universally recommended that these teeth be reinforced with a post and core, and covered with a crown.
(insert labeled diagram series here)