Root canal therapy is a procedure that involves cleaning, disinfecting, and sealing the central, small, hollow, inner space of a tooth. This space is where the blood vessels, nerve, and connective soft tissue of the tooth reside. Think of this space as the hollow part of a reed, only very small. Contamination of the space by bacteria, usually from decay or trauma to the tooth, can result in infections within the center of the tooth that dentists call abcesses. These infections can be painful, and can spread out the end of the tooth into the surrounding tissues. This can result in damage to adjacent structures such as, bone, adjacent teeth, sinuses, etc.
Dentists gain access to these infections by a hole drilled through the crown of the tooth into the center of the tooth where the canal(s) exists. Once accessed, the canal spaces are debrided, cleaned, shaped and disinfected using small mechanical or hand files. The canal space is then sealed and filled with a permanent material. Because the connective tissue and blood vessels are only needed during the original formation of the tooth, and not after, removing this tissue does not adversely effect the tooth. Depending upon the amount and location of the infection, the dentist may also use antibiotics to help clear up the infection.
Teeth that have had root canals are far more likely to fracture than teeth that have not had root canals. It is common to place crowns on root-canaled teeth to help prevent fractures. Untreated decay is the most common cause of abcesses. Therefore, early diagnosis/treatment of decayed teeth is definitely in the best interest of the patient.