External cervical resorption is an uncommon condition in which a tooth is broken down from the outside, starting at the neck of the tooth near the gum line. The process is painless for a long time, which is why the damage is usually found on an X-ray, or because of a lump in the gum, rather than because anything hurts.
External cervical resorption is a process in which the body’s own cells break a tooth down from the outside, starting at the neck of the tooth close to the gum line. The damage works inwards, hollowing out tooth structure that cannot grow back.
The condition is uncommon, and in the early stages causes no pain at all.
A knock to a tooth is the commonest trigger, and the gap between the injury and the damage appearing is often decades. Most people have long forgotten the original accident.
Other recognised triggers include orthodontic treatment, internal whitening of a root-filled tooth, gum treatment and surgery around the tooth. In a proportion of cases no cause is ever identified.
The process begins on the outer surface of the tooth, away from the nerve, and advances slowly. Pain tends to appear only once the damage reaches the nerve, or once infection follows.
By the time a tooth becomes uncomfortable, the resorption has usually been present for a long time.
Most cases are found on a routine X-ray, with no complaint from the patient at all.
Where signs do appear, the commonest are a lump in the gum beside the tooth, a pink or darker patch showing through the enamel near the gum line, or a tooth that gradually changes colour. None of those signs is painful, and any one of them is worth having looked at.
A flat X-ray shows that something is present, but not how far the damage has gone. External cervical resorption wraps around the tooth in three dimensions, and a single flat image compresses that shape into one plane.
A CBCT scan shows the true extent: how deep the defect runs, how far below the gum the margin sits, and whether the nerve is involved. Examination under the dental operating microscope then shows the surface of the defect directly.
Those two findings together are what decide whether a tooth can be kept.
Treatment means reaching the defect, removing the resorptive tissue, and sealing the cavity so the process cannot continue. Gum is often recontoured first, so that the margin of the defect can be seen and kept dry.
Where the resorption has reached the nerve, or the nerve has already died, root canal treatment is needed alongside the repair.
Where the defect runs too deep below the gum to be reached and sealed, keeping the tooth may not be realistic. Finding that out early, and saying so plainly, matters as much as the treatment itself.
External cervical resorption does not stop on its own, and a tooth cannot repair the damage. A defect caught while still small and above the gum is far more straightforward to treat than one that has spread below the bone.
That is the argument for having a lump in the gum, or an unexplained change in tooth colour, assessed rather than watched.
A man in his forties with no symptoms at all, who noticed a lump in his gum. The cause traced back to a knock taken during a football match as a teenager.