Endodontics (Root Canal Treatment)

Normal Healthy Teeth

A normal healthy tooth is divided into two parts. The part of the tooth that is visible above the gum line is called the "crown" and that which is hidden under the gum is the root.

Teeth are held in the jaw by their roots. Front teeth normally have one root, but teeth further back in the jaw will have two or three and sometimes more. Each tooth is supplied with nerves and tiny blood vessels which enter the tooth through the tip of each root. The blood vessels carry nutrients and waste to and from the tooth. The nerves give feeling to the tooth and like all nerves in the body they act as an early warning system indicating injury, the onset of infection or disease.

Pulp

Both the nerves, blood vessels are housed in an area deep within the tooth called the pulp. The pulp is further divided into two parts which comprises the nerves or root canals which lie within each root and the pulp chamber which is found within the "crown".

Symptoms

When a tooth is healthy the nerves are alive. However, bacteria can enter the pulp through a loose filling, decaying cavity, a crack, or if injury exposes the nerves. Symptoms of nerve infection are often sensitivity to hot and cold foods, throbbing, aching, pain on chewing and swelling. Sometimes there are no symptoms and occasionally the only indication that the tooth is dead is that it turns grey or black in colour.

Abscess

In time the bacteria kills the pulp which contains the nerves and blood vessels. Unless there is a hole in the pulp, the only way the infection can escape is through the root opening where the nerves and blood vessels enter the tooth. The bone surrounding the root traps the infection so it forms an abscess around the root tip. The abscess creates pressure which can cause great pain and swelling. Long-term the abscess can destroy the bone supporting the tooth so causing it to become loose. Equally, the abscess can push the tooth partly out of its socket and stretch the periodontal ligaments which holds the tooth firmly in place so causing it to become loose.

On occasions, the pressure of the abscess causes the infection to create a drainage hole in the bone which may emerges between the gum and the root allowing the pus to escape in a continually discharging abscess. The escaping pus can also collect under the gum and form a "gum boil"

Why Root Canal Treatment?

It is highly likely that a tooth with a dead or dying nerve will have to be removed if it is not root treated. Although symptoms can sometimes subside, a dormant abscess often remains at the root tip which can flare up at any time.

When Is Root Canal Treatment Necessary?

Apart from bringing an unhealthy tooth back to health, a tooth requiring either a filling, crown or bridgework to restore it, but whose nerves are dead or dying and have not previously been root treated, will require root canal treatment before restoration work begins.

Failure to do so means that expensive dental work would have to removed, possibly destroyed and replaced with new in order to access the diseased nerves. Even though a dormant abscess may have been present and symptomless for a long time before any restoration work begins, it is highly likely that treatment will re-infect the abscess and painful symptoms reappear.

Reasons for Not Undertaking Root Treatment

The time and expense involved in root canal treatment means that some patients may decide to remove the tooth rather than save it. A tooth may be so decayed and broken down that it is impossible to restore it.

Treatment

Treatment may take one or two visits. Once the tooth has been numbed, a small rubber sheet or rubber dam is fitted around the tooth to isolate it from the others. The rubber dam has several functions:

1. Prevents bacteria contained within saliva from entering and re-infecting the nerve canal.
2. Prevents chemicals (bleach) used in sterilising canals from entering the mouth.
3. Prevents very small files and instruments which may be inadvertently dropped from falling down the throat.
4. Isolating the tooth allows the nerve canals to stand out in better contrast.

The dentist needs to make an opening in the tooth by removing an existing filling and decay. If a tooth is crowned it may necessitate making a hole in the crown or possibly removing it altogether to reach the nerves.

Narrow files are then used to remove the nerves. Once the nerves are removed, the nerve canals are then cleaned and sterilised. The nerve canals are then filled with gutta-percha, a firm rubber like material which seals them and prevents further infection entering.

Restoration

Once root treatment is completed, the access hole at the top of the tooth has to be filled in using either a permanent metal or white filling. On occasions a crown may be necessary to restore the tooth, but sometimes prior to fitting the crown, a post has to be cemented into the nerve canal to strengthen the tooth, or help retain the restoration. If decay was extensive prior to root treatment, the decayed tissue has to be replaced with a filling material which acts as a foundation core over which a new crown is fitted.

Long Term Predictability

Because of the complex anatomy of the root canal system, it is a recognised fact that it is impossible to completely eliminate all bacteria. Root canal therapy therefore cannot be guaranteed 100% and carries a 10 - 15% failure rate.

Root treated teeth are also dead and weaker than living teeth and carry the additional recognised risk of fracturing under pressure. Even those root treated teeth that are reinforced with posts to support either crowns or bridges, carry the same risk of fracture.

However, with care and attention most root treated teeth can and do last many years.

Consequences

If teeth are lost because of failure to undergo root treatment, there are possible long-term consequences. Missing teeth, especially those at the front where they are most obvious, will require either dentures, bridges and implants to fill the gap and whose costs can be far greater than root treatment itself.

Teeth are only held in position by adjacent and opposing teeth. Once a tooth or teeth are lost, it can allow adjacent teeth to move or tilt out of position causing spaces and recesses to develop which become traps for plaque and food that increases the future risk of decay and gum disease.

Teeth opposite gaps caused by missing teeth can overgrow and become out of alignment. Teeth can overgrow to such an extent, that if it is later decided to fill the space, the overgrown teeth may have to be cut down and crowned to allow room for the new replacement teeth. Movement of teeth may prevent or interfere with the correct way that top and bottom teeth close together (occlude). This may long-term cause abnormal wear and sensitivity of the teeth, plus possibly cause pain and clicking of the jaw joint.

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