There are several scenarios in which the tooth pulp can become diseased. The disease process is generally related to germs (ie. an INFECTION) or due to tissue irritation (INFLAMMATION).
Infectious disease: The mouth is full of bacteria (germs). Through life, these germs attack the teeth. Certain types of oral bacteria produce acid. The acid that is produced burns a hole in the tooth. Commonly, these holes are referred to in more technical language such as “cavities”, “caries”, or “tooth decay”. Sometimes the infection penetrates so deeply into the tooth that the tooth pulp is breached. Other scenarios in which bacteria may penetrate into the tooth are cracks or leaky restorations.
The presence of bacteria in the root canal system may lead to a toothache (due to the germs irritating the pulpal tissues) or it may lead to a silent death of the tooth.
Toothache:
Exaggerated pain to cold/hot and throbbing or spontaneous pain may be the result of inflammation in the tooth. A good example of the irritation of inflamed tissue elsewhere in the body occurs when one has sunburn and then takes a hot shower. When the skin has been irritated by the sun (ie. is inflamed), a relatively minor stimulus such as hot water is suddenly quite painful. The same holds true in the tooth. When the pulp tissue is inflamed, normal stimulation such as room temperature foods and cold air are painful.
The presence of spontaneous or lingering pain indicates that the pulp is diseased and not likely to recover on its own. One option is to extract the tooth. The other option is to perform root canal therapy (see below).
Although a primary reason for inflammation is bacterial invasion, other reasons can include multiple procedures to the tooth such as large fillings or crown preparations.
Infection:
Sometimes the tooth dies silently. Once the pulp tissue is dead, there is no longer blood flow into the root canal space. Therefore, the body’s immune system is not able to protect the tooth against bacterial invasion. When bacteria overwhelm the root canal space, they can then influence the bone around the body. This may result in irritation to the bone surrounding the tooth, or can lead to infection in the body or soft tissues of the mouth. Changes to the bone are generally diagnosed by taking radiographs (x-rays).
Symptoms of infected teeth include no sensation of cold or hot, but pain to biting or chewing. Sometimes the presence of infection such as an abscess leads to the diagnosis of a root canal infection.