Root canal treatment

Root canal treatment has the worst reputation of anything in dentistry, and most of that reputation is forty years out of date. It is carried out under local anaesthetic, it is the treatment that relieves severe toothache rather than causing it, and the alternative to it is losing the tooth.

Why a tooth needs it

At the centre of every tooth is the pulp — nerves, blood vessels and connective tissue — running from a chamber in the crown down narrow canals inside each root. When bacteria reach it, usually through deep decay but sometimes through a crack, a leaking filling or an injury to the tooth, the pulp becomes inflamed and then infected. It cannot recover once infection is established, because there is no room inside a rigid tooth for the swelling that would normally be part of healing.

Infection then spreads out of the end of the root into the bone, which is an abscess. The pattern is usually recognisable: severe throbbing pain, often worse with heat and worse lying down, sometimes relieved briefly by cold; then, when the pulp dies, a deceptive period of no pain at all; then pain on biting, tenderness, a bad taste, or facial swelling.

Root canal treatment removes the infected tissue, cleans and shapes the canals, and seals them so that bacteria cannot recolonise. It does not remove the tooth's attachment or its blood supply from outside, so a root-filled tooth stays firmly in place and works normally.

The honest framing of the choice is this: root canal treatment keeps the tooth, extraction does not. Extraction is a legitimate option, and sometimes the better one — a tooth with too little structure left to restore, or severe gum disease as well, may not be worth saving. But a gap at the back has consequences of its own, and the teeth either side of it are sound teeth that would have to be involved in any bridge. It is a decision to discuss rather than one that makes itself.

What the treatment involves

Local anaesthetic first — the same as for a filling, and a tooth with an acutely inflamed pulp sometimes needs more than usual, which is worth saying rather than enduring.

The tooth is then isolated with a rubber dam, a small sheet clipped around it. This is not optional detail: it keeps saliva and its bacteria out of the canals being cleaned, and it stops anything being swallowed. A small opening is made through the biting surface or the back of the tooth into the pulp chamber, and the canals are located.

Each canal is cleaned with fine files and flushed with a disinfecting solution, which does most of the actual work of removing bacteria. The length of each canal is measured, by X-ray and usually by an electronic device, so that the cleaning reaches the end of the root and no further. The canals are then dried and filled with gutta-percha, a rubbery material, with a sealer.

Finally — and this matters as much as anything that happened inside the tooth — the opening is sealed. A leaking seal at the top lets bacteria back in and is a common reason for failure, so a temporary filling is a holding measure rather than a finish.

It takes one or two appointments, sometimes more for a molar with several curved canals. Where it is done over two visits, an antibacterial dressing is left inside between them.

Afterwards, and the crown question

The tooth is often tender to bite on for a few days, occasionally longer, as the inflammation in the surrounding bone settles. Paracetamol or ibuprofen by the label covers it. Worsening pain, swelling or pain that is still significant after a week is a reason to go back.

A root-treated tooth is more brittle than it was, because the pulp chamber and canals have been opened up and the tooth has usually lost structure to decay as well. A back tooth will normally need a crown or an onlay to stop it splitting, and a tooth that splits below the gum line is usually unsaveable. Where a crown is advised, having it is not an upsell; delaying it indefinitely is how successfully treated teeth get lost. Front teeth with small access openings can often be restored with a filling alone.

Front teeth that have been root-treated sometimes darken over the years. That is dealt with by bleaching from inside the tooth rather than from outside, which is a different procedure from ordinary tooth whitening.

One thing to note: a root-treated tooth has no nerve in it, so new decay around a filling or under a crown can progress a long way without hurting. It needs examining like any other tooth, and arguably more attentively.

When it does not work

Root canal treatment succeeds in the large majority of cases, but not all. Canals can be narrow, curved, blocked or simply hard to find; a missed canal is a common reason for persistent infection; and bacteria can re-enter through a leaking restoration years later.

Where it fails, the options are re-treatment — reopening the tooth, removing the old filling material and cleaning again, which is slower and more difficult than the original and often done by a specialist — or an apicectomy, a small operation to remove the tip of the root and seal it from the end, or extraction. Failure is not automatically the end of the tooth.

Antibiotics are not a treatment for an infected pulp. They cannot reach inside a tooth with no blood supply, so they damp the symptoms down temporarily while the cause remains, and the infection returns when the course ends. They have a place where infection is spreading or someone is unwell, as a holding measure alongside treatment rather than instead of it.

The claim that root canals cause illness

This circulates persistently, usually as a claim that root-filled teeth harbour bacteria that cause chronic disease or cancer. It descends from the focal infection theory of the early twentieth century, which held that many systemic illnesses originated in the mouth and led to a great many healthy teeth being extracted for no benefit. The theory was abandoned decades ago because the evidence did not support it, and no reputable body endorses extracting root-treated teeth to prevent systemic disease.

It is worth saying plainly because the practical consequence of believing it is having sound, functioning teeth removed — and because the people who promote it are generally selling the removal.

See also tooth decay and cavities, fillings, crowns and implants and paying for dental care.