Root canal

Root canals are the long passages full of soft tissue deep within the dentin of a tooth, adjoined the pulp chamber. In dentistry, a pulpectomy is an endodontic treatment to cure an infection of the root canal; informally a root canal. A root canal, coupled with internal tooth bleaching, is also used to fix teeth that have blackened due to infiltration of decayed soft tissue into the dentin in the teeth, most often seen in frontal incisors that have been injured through a sudden impact.

Tooth structure

At the center of a tooth is a hollow area that houses soft tissue, known as pulp. This hollow area contains a relatively wide space towards the chewing surface of the tooth called the pulp chamber. This pulp chamber is connected to the tip of the root of the tooth via thin hollow pipe-like canals—hence, the term "root canal". Human teeth normally have one to four canals; teeth toward the back have the most canals. These canals run through the centre of the roots like pencil lead runs through the length of a pencil. The tooth receives nutrition through the blood vessels and nerves traversing these canals. Occasionally, a cavity on the outside of the tooth may allow this soft tissue to become infected. If left untreated a serious jaw infection can result. The infection and inflammation is very painful in most cases. Ideally treatment should take place before this happens.

Root canal treatment

Sometimes a tooth is considered so threatened (due to internal cracking etc) that future infection is considered likely or inevitable, and a pulpectomy is advisable to prevent it. But usually some inflammation and/or infection is already present, within or below the tooth. To cure the infection and save the tooth, it is necessary for the dentist to drill into the pulp chamber, and remove the infected pulp by scraping it out of the root canals. Once that is done, the dentist fills the cavity with an inert material and seals up the opening. This procedure is known as root canal therapy. If enough of the tooth has been damaged, or removed as a result of the treatment, a crown may be required.

The standard filling material is Gutta-percha, a thermoplastic polymer of isoprene, which is melted and injected to fill the root canal passages. Barium is added to the isoprene so the material will be opaque to X-rays, allowing verification afterwards that the passages have been properly completely filled in, without voids.

For patients, root canal therapy is one of the most feared procedures in all of dentistry; contrary to popular belief, however, modern root canal treatment may be relatively painless due to effective pain control techniques. Lidocaine is a commonly used local anesthetic. Pain control medication may be used either before or after treatment. However, in some cases it may be very difficult to achieve pain control prior to performing a root canal. For example, if a patient has an abscessed tooth, with a swollen area or "fluid-filled gum blister" next to the tooth, the pus in the abscess may contain acids that inactivate any anesthetic injected around the tooth. In this case, it is best for the dentist to drain the abscess by cutting it to let the pus drain out. Releasing the pus releases pressure built up around the tooth; this pressure causes much pain. The dentist then prescribes a week of antibiotics such as penicillin, which will reduce the infection and pus, making it easier to anesthetize the tooth when the patient returns one week later. The dentist could also open up the tooth and let the pus drain through the tooth, and could leave the tooth open for a few days to help relieve pressure. At this first visit, the dentist must ensure that the patient is not biting into the tooth, which could also trigger pain. Sometimes the dentist performs preliminary treatment of the tooth by removing all of the infected pulp of the tooth and applying a dressing and temporary filling to the tooth. This is called a "pulpectomy." The dentist may also remove just the coronal portion of the dental pulp, which contains 90% of the nerve tissue, and leave intact the pulp in the canals. This procedure, called a "pulpotomy," tends to essentially eliminate all the pain. A "pulpotomy" may be a relatively definitive treatment for infected primary teeth. The pulpectomy and pulpotomy procedures eliminate most all pain until the follow-up visit for finishing the root canal. But if the pain returns, it means any of three things: the patient is biting into the tooth, there is still a significant amount of sensitive nerve material left in the tooth, or there is still more pus building up inside and around the infected tooth. All of these cause pain.

After removing as much of the internal pulp as possible, the root canals can be temporarily filled with calcium hydroxide paste. This strong alkaline base is left in for a week or more to disinfect and reduce inflammation in surrounding tissue.^* Ibuprofen taken orally is commonly used before and/or after these procedures to reduce inflammation.

After receiving a root canal, the tooth should be protected with a crown that covers the cusps of the tooth. Otherwise, over the years the tooth will almost certainly fracture, since root canals remove tooth structure from the tooth and undermine the tooth's structural integrity. Also, root canal teeth tend to be more brittle than teeth not treated with a root canal. Placement of a crown or cusp-protecting cast gold covering is recommended also because these have the best ability to seal the root canaled tooth. If the tooth is not perfectly sealed, the root canal may leak, causing eventual failure of the root canal.

The procedure is often complicated, depending on circumstances, and may involve multiple visits over a period of weeks. The cost is high, typically at least $US 1,000 -- though exceeded by the even more expensive related crown procedure, typically around $US 2,000.

Innovation

In the last 10-20 years, there have been great innovations in the art and science of root canal therapy. Dentists now must be educated on the current concepts in order to optimally perform a root canal. Root canals have become more automated and can be performed faster, thanks to advances in automated mechanical instrumentation of teeth and more advanced root canal filling methods. Dentists also possess newer technologies that allow more efficient, scientific measurements to be taken of the dimensions of the root canal that must be filled. Many dentists use microscopes to perform root canals, and the general consensus is that root canals performed using microscopes or other forms of magnification are more likely to succeed than those performed without them. Although general dentists are becoming versed in these advanced technologies, they are still more likely to be used by specialist root canal doctors (known as endodontists). An Italian dentist named Arnaldo Castellucci has recently authored a 3-volume treatise on Endodontics which thoroughly covers these modern concepts.

Laser root canal procedures are a controversial innovation. Lasers may be fast but not thoroughly disinfect the whole tooth, and may cause damage.^*

Failure

Sometimes root canals fail. Patients should be educated on some of the reasons why root canals may fail. They may fail if the dentist does not find, clean and fill all of the root canals within a tooth. For example, on a top molar tooth, there is a more than 90% chance that the tooth has four canals instead of just three. But the fourth canal, often called a "mesio-buccal," tends to be very difficult to see and often requires special instruments and magnification in order to see it. So, it may be missed, and this infected canal may cause a continued infection or "flare up" of the tooth. Any tooth may have more than one canal, which may be missed while performing the root canal. Sometimes the canal may be unusually shaped, making it impossible to fill it completely, so that some infected material is still left in the canal. Sometimes the canal filling does not extend deeply enough into the canal, or it does not fill the canal as much as it should. Sometimes a tooth root may be perforated while the root canal is being performed, making it difficult to fill the tooth. The hole may be filled with a material derived from natural cement called "MTA," although usually a specialist would perform this procedure. Fortunately, a specialist can often re-treat and definitively heal up these teeth, often years after the initial root canal procedure.

Alternatives

Claims have been made that it is impossible to fully sterilize a tooth internally, or fill it in a perfectly inert biocompatible permanent fashion. There is an ongoing risk of infection, which may pose dangers to the rest of the body. Unfortunately, there is generally no satisfactory alternative. Pulling the tooth leaves a gap which poses both aesthetic and functional problems, and endangers the structure of the adjacent teeth.^*Weston Price conducted research on root canals and wrote two books about how toxic they can be. The pain associated with a failed root canal can be very intense.

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