Anatomy

The root canal is a space within the root of a tooth that contains the pulp, which consists of nerves, blood vessels, and connective tissue.  These tissues are essential during tooth development to allow proper root formation.  After the tooth is fully formed, the pulp tissues provide a feedback response to irritants, such as bacteria and their toxins.  The pulp is vulnerable to bacteria and can become inflamed or infected by a rapidly approaching cavity.

Etiology

The main cause of a tooth infection is bacteria.  The immune system within the pulp can defend itself from small amounts of bacteria, but it can easily be overwhelmed as the bacteria increase.  An infected root canal can lead to a condition known as apical periodontitis, which is inflammation and loss of bone around the root tips.  Apical periodontitis may be asymptomatic or may present as discomfort to chewing, biting, or tapping the tooth.  Sometimes pain is spontaneous and without provocation.

Endodontists are specialists in treating disease of the pulpal and periapical tissues.  The focus of endodontics is to prevent or cure inflammation of the periapical tissues through root canal therapy, root canal retreatment, and apical surgery.  These procedures are aimed at the elimination of bacteria within the root canal system.  The ultimate goal is to save your tooth.

Root Canal Treatment

The goal of root canal treatment is to prevent the migration of bacteria and inflammation into the surrounding tissues, or to resolve an already established infection.  Root canal treatment involves removing the inflamed or infected tissue from the root canal system of a tooth.  After the canals have been adequately cleaned, shaped, and disinfected, a filling is placed in the canals and the tooth is restored with a filling or a crown.

Depending on the complexity of the case or degree of infection, a root canal will usually take 1 or 2 visits for completion.  A follow-up of 1 year is performed to assess the degree of healing or to ensure that infection has been prevented.

Upper molars cause problems due to the second canal located in the mesiobuccal root.  Failure to locate and instrument this second canal can result in the development of post-treatment endodontic disease.  

Root Canal Retreatment

Sometimes a root canal treated tooth fails to heal.  This may be due to inadequate disinfection of the root canal, resulting in a persistent infection.  On the other hand, a root canal can become re-infected due to a leaky restoration, a crack in the tooth, or a new cavity.  Under these circumstances, retreatment of the root canal can be performed.

Lower premolars can present a challenge when containing multiple canals.  The following case demonstrates how the bone around an infected root canal treated tooth healed following non-surgical retreatment.
 

Apicoectomy

Obstructions such as posts, separated instruments, or blocked canals may prevent non-surgical access to the root canal system.  A complex anatomy may also protect bacteria from disinfection during the original root canal procedure.  In these cases, a surgical approach can be taken to remove tip of the infected root, where the persistent bacteria reside.  A filling is then placed in the back end of the root to seal root canal and prevent any future infection.

The following tooth #14 received two non-surgical retreatment procedures, both of which failed to eliminate the source of the infection.  Following an apicoectomy, the bone around the root tips completely healed.
 

Traumatic Injury and Cracked Teeth Management

Traumatic dental injuries can also managed by endodontists.  In the event of a fractured, displaced (luxated), or knocked-out (avulsed) tooth, an endodontist is trained to provide the best treatment for tooth retention and preservation of the supporting dental structures.  Timely treatment following a traumatic injury is paramount as the chance of saving a traumatized tooth declines with time.

Sensitivity to cold or chewing may be an indication of a cracked tooth.  A crack in the enamel can allow air and liquids to stimulate the nerves that are otherwise protected from exposure.  Bacteria and their toxins may also be able to gain entry through the crack and cause inflammation within the pulp.  A crack may also propagate vertically and cause more extensive damage to the crown and root of the tooth.  Therefore, it is important to seek treatment at the first signs of a potential cracked tooth. 
 

Emergency Treatment

Many times a root canal infection may remain asymptomatic throughout its development.  Alternatively, root canal infections may also present with pain and swelling, which can develop quickly without warning.  The job of the endodontist is not to cause pain but rather to relieve pain.  Emergency treatment is focused on the alleviation of pain and/or swelling through cleaning of the root canal system, and administration of appropriate pain medications and antibiotics.  Every step will be taken to ensure that the procedure is done as painlessly as possible.

The patient below knocked out her front tooth on the playground.  The tooth was not replanted at the scene of the accident, so therefore root canal therapy was performed on the tooth prior to its replantation.  Considering this tooth spent more than 24 hours out of the socket, the prognosis is guarded and the tooth may eventually require replacement with an implant.  But at a young age, the root canal treated tooth will serve to preserve the bone until a more definitive restoration can be done.  Special thanks to James Han, D.D.S, M.B.A. for his integral role in this case.

Revascularization/Regeneration

In the case of an immature tooth that develops an infection, continued root growth ceases.  A revascularization procedure allows disinfection of the root canal with the potential re-establishment of the blood supply to the tooth.  This re-established blood supply can generate new tissue within the tooth which may allow for continued root growth.  Revascularization is one of the newest concept in endodontics and provides a gateway to potential regeneration of teeth and other structures of the oral cavity through stem cell research.

The following case depicts closure of a wide canal apex with MTA.  After thorough disinfection of the canal space, an MTA plug was place at the canal apex.  The MTA sealed the apex and allowed the compaction of gutta percha to fill the rest of the canal space.  Significant healing was seen at the 18-mo follow-up.

Additional Endodontic Case Examples

This case involved internal resorption of both the mesial and distal roots of tooth #30. These cases require a vital pulp and often present as asymptomatic. Upon completion of root canal therapy, the pulpal cells responsible for the resorption were removed and the resorptive process stopped.

The following molar represents a case of radix entomolaris, which simply means an extra root in a mandibular molar tooth. Most mandibular molar teeth have two roots. This tooth had three roots and four canals.

This patient presented with mild symptoms associated with the maxillary incisors. Radiographs showed periapical radiolucencies on teeth #’s 8, 9, and 10, indicating the presence of post-endodontic disease. The decision to perform apicoectomies was chosen over non-surgical retreatments mostly due to financial considerations. Complete healing of the periapical tissues was seen at the 9-month recall visit.

Wisdom teeth can also be treated with root canal therapy if the symptoms should indicate the need, and the tooth is functional and restorable. Tooth #32 served as a distal abutment for a 4-unit bridge, and was symptomatic to hot and cold. Pulpal sensitivity testing produced results consistent with irreversible pulpitis.

This patient presented with post-treatment endodontic disease.  A separated instrument was noted at the apex of the mesial root.  Non-surgical retreatment was first performed under the assumption that the separated instrument was not going to be retrieved or potentially bypassed. Despite not removing the instrument, reducing the bacterial load below a certain threshold is sometimes enough to allow for apical healing. Nine months following the retreatment, apical healing was not apparent and therefore apicoectomy was performed. The 12-month recall showed that the apical tissues completely healed.