The Root Canal Procedure

Before taking the decision of proceeding to a root canal treatment, the dentist must make sure that the pulp/nerve is not alive. If the tooth does not respond to hot or cold stimuli, it is an indication that the pulp is dead. Some dentists use a device called electric pulp tester to identify the condition of the pulp. The results of these tests will indicate whether or not an endodontic procedure is necessary.

The first step is to identify the tooth with the problem. This might not be as simple as it sounds, since sometimes the pain is so strong that it radiates to adjacent teeth, making it difficult to understand where the source of the pain is. In some cases, an x-ray might be needed to provide evidence of an abscess at the end of the infected tooth.

Preparation for root canal treatment

If there is inflammation and swelling, the dentist may prescribe an antibiotic or/and anti-inflammatory medicine for some days before starting the root canal procedure. The purpose is to control the infection and to ease the swelling which can make the anesthetic less effective. If the condition is painful, the patient will have to take an over the counter or prescription analgesic to relieve the tooth pain until the procedure.

The next step in the procedure is to take an X-ray to check the shape of the root canals and determine if there are any signs of infection in the surrounding bone.

Anesthesia

Anesthesia may not be necessary, since the nerve is usually dead, but most dentists still use anesthesia to make the patient more relaxed. The tooth and the surrounding area are completely numbed with one or more injections of local anesthesia.

Root canal treatment is a delicate procedure that requires precision by the dentist. As the process can take some time it is important that the patient remains comfortable and relaxed throughout the procedure. In addition to anesthetic, a dentist may use dental sedation, such as nitrous oxide, oral sedation, or IV sedation in cases of severe dental anxiety.

Isolating the tooth

Before the dental pulp is exposed, the dentist will place on the tooth a device called rubber dam. It is a rubber sheet places around the tooth and held in place by a small clamp that grasps to the tooth. The purpose of the rubber dam is to isolate the tooth, keep it dry and prevent the contamination of the tooth by saliva bacteria during the root canal procedure.

Gaining access to the dental pulp

In order to perform the root canal treatment, the dentist must gain access to the infected pulp area inside the tooth. First, the dentist will remove any tooth decay from the crown of the tooth. Then, an opening is drilled through the crown into the pulp chamber, over the position where the dentist expects to find the nerve. On the back teeth the access hole is made on the chewing surface of the tooth, while in front teeth the hole is made on the lingual side of the tooth, to keep it off sight.

Opening the dental pulp chamber relieves the pressure inside the tooth and offers significant pain relief.

Measuring

It is important for the dentist to know the exact length of each root canal. If the length is measured shorter than actual then it is possible that the end tip of the root canal will not be cleaned or sealed properly. If it is estimated longer than actual, the instruments used for cleaning the canal (or the filling material) may get beyond the edge of the canal injuring the periodontal ligament and the jaw bone.

The dentist removes some of the infected or dead pulp tissue until the root canals location is revealed. A root canal file is carefully placed in each of the root canals and one or more x-rays are taken. By examining the x-rays and measuring how close the file is to the end of the root canal, the dentist can calculate the exact length of each root canal.

Another option in measuring the length of the root canals is an electronic device called ‘apex locator’. The device can provide an accurate length calculation of the distance from the pulp chamber to the tip of the root (apex). Some times both methods are used in combination, for better accuracy.

Root canal files are small instruments that look like flexible pins with serrations along their length. They are available in sets of different sizes with increasing diameter. There are 3 kinds of root canal files:

• Root canal broaches that are used to remove (extirpate) the pulp from the root canal.
• Root canal reamers that are used to enlarge the root canal.
• Root canal files that are used to enlarge and smooth the walls of the root canal.

Cleaning

After the canals have been measured, the dentist or endodontist will start the cleaning procedure that involves the removal of bacteria, nerve and dead tissue debris from the interior of the tooth.

First, any remaining pulp tissues are removed from the pulp chamber with the use of a slow speed handpiece (drill). After the pulp chamber is cleaned the dentist inserts endodontic files into the root canal to remove the nerve from inside the canal. When the nerve is removed, the root canal has to be slightly enlarged, shaped and smoothed for the correct application of the filling material in the next step.

The dentist or endodontist will start with a very thin file followed by progressively larger diameter files until the entire mass of the nerve is removed and the sides of the root canals are made smooth and clean. After each pass with the endodontic files, the pulp chamber and the root canals are irrigated with a dilute solution of laundry bleach in order to wash out bacteria, dead tissue and debris, and to sterilize and chemically neutralize any dead tissue that may be missed by the files. Instead of bleach solution, some dentists use a solution of chlorhexidine. Chlorhexidine is a strong antiseptic that is less caustic and foul tasted than bleach if it gets in contact with the mouth beyond the rubber dam.

Cleaning the root canals is the most critical part of the dental root canal procedure. The dentist has to be careful to clean all the infected tissue, do not miss any root canal or branch of and use the files exactly up to the measured length of the root canal, no less – no more. The procedure is usually performed by the dentist by hand, moving up and down and twisting the endodontic file inside the root canal, in order to scrape and scrub the sides of the canal. Other options include the attachment of the file to a low speed handpiece or using ultrasonic equipment.

The cleaning phase of a root canal procedure might need more than one appointment, especially in cases when the dentist suspects that the root canals are branched in a way that infected tissue and bacteria might be left in areas that the dentist can not see or the files can’t reach. In these cases, the dentist will put antimicrobial medication in the pulp and canal area to kill any remaining bacteria and will use a temporary filling to protect the tooth until the next visit.

The dentist may decide to leave the tooth open for a few days to allow drainage of a periapical abscess and prescribe an antibiotic to stop the infection. If the infection is not controlled until the next appointment, the process is repeated.

Filling the root canal

For a root canal treatment to be successful, the tooth should never be permanently filled and sealed before it is completely free of active infection. Some dentists wait for a week or more after the root canal procedure before they proceed to the filling of the tooth. Of course, if a dentist is sure that the infection is sustained and the tooth is completely cleared, there is no problem in finishing the root canal treatment in one single appointment.

When the dentist decides that it is safe, he will dry the interior of the root canals with paper points and start to fill them with a permanent root canal filling material. The material used for the filling is often a biocompatible rubber-like material called “gutta percha” in combination with an antibacterial cement (sealer). Gutta percha is a pink colored root canal filling material shaped in cones that come in different diameters in order to match the files which are used to clean out the inside of the tooth and fit exactly to each root canal. The creamy sealer is inserted first in the root canal or it is applied to the cone's surface. Then the dentist inserts the gutta percha cone carefully into the canal exactly up to the tip of the root. This is the phase where the measuring of root canal’s length and diameter, done in previous phases comes to use. Additional gutta percha cones may be placed besides the first one to fill the entire root canal. The dentist uses the gutta percha cones to put pressure on the soft creamy cement so that it is forced against the canal’s walls and into every tiny branch of the canal.

The purpose of the process is to seal completely the canal from its environment, to prevent bacteria from entering the tooth in the future. Sometimes the gutta percha is warmed (or applied with a thermal ‘gun’) to better adapt to the precise shape of the interior of the tooth.

If the tooth has suffered significant damage from tooth decay and it is unable to support a crown, the dentist will place a metal post in the pulp chamber to provide structural support for the crown restoration.

As soon as the root canals are filled, the opening at the crown of the tooth can be sealed with a permanent filling but usually a temporary filling or crown is used until a permanent restoration may be made.

After the tooth is sealed, the root canal treatment is considered completed. The crown of the tooth should then be restored with a permanent filling or crown within a relatively short time.

Restoring the Tooth After Root Canal

After the completion of the root canal procedure only the interior of the tooth is treated. The external surface of the crown has to be restored for the tooth to get back its form and functionality. The final tooth restoration should not be postponed for a long time (no more than a month) because it increases the risks of a re-contamination of the tooth. Another problem is that the tooth remains weak until restored, and it will fracture easily if pressured.

Depending on the general condition of the tooth and the amount of tooth structure lost, the dentist will decide if a permanent composite filling is enough or a crown should be placed. Endodontically treated teeth often become brittle with time after treatment. Crowning the tooth is usually safer, especially if a molar is involved. A crown or a crown and post are cemented on the tooth to strengthen its structure and improve appearance, by a general dentist or a prosthodontist. With properly performed root canal procedure and restoration, a treated tooth can function normally for a lifetime.