Notches at the gum line: wear or tooth decay?

What the notch looks like and where it appears

You usually notice it when your fingernail catches or when you look in the mirror: a small hollow on the cheek side of a tooth, right where it meets the gum. This area is called the neck of the tooth; the enamel ends here and the root begins. The hollow can be a sharp-edged V or a shallow, rounded dip. It is most common on premolars and canines, often on several teeth at once, and becomes more frequent with age. Dentists call it a ‘non-carious cervical lesion’ (cervical means the neck of the tooth): the hollow is caused not by bacteria but by tissue being lost gradually over many years.

Three possible causes, often working together

A notch rarely has a single cause. The three processes below tend to reinforce each other: acid softens the surface, and the brush then wears the softened surface away more easily. The shape of the hollow gives a clue but does not prove the cause on its own.

• Abrasion (mechanical wear): a hard-bristled brush, scrubbing sideways, pressing too hard or an abrasive toothpaste. Studies most often point to brushing method and frequency, but according to one systematic review the data are largely inconclusive.
• Erosion (acid wear): acidic drinks, frequent citrus fruit or vinegary foods, reflux or repeated vomiting. Acid dissolves enamel without any bacteria involved, and the hollow it leaves is usually shallower and more rounded.
• Abfraction (loss from flexing): the idea is that stress building up at the neck of the tooth during clenching or grinding breaks enamel away in tiny fragments. Sharp-edged, V-shaped notches are often explained this way.

Why the role of clenching and grinding is debated

The idea of abfraction rests largely on laboratory tests and computer models: a strong bite flexes the tooth very slightly, and the stress gathers at the neck. Studies in patients do not show the same clear picture. A systematic review of the link between the bite (the way the upper and lower teeth meet) and these notches found that the studies differed widely in design and diagnostic criteria, and that the role of the bite has not yet been established. So clenching your teeth does not show that it caused your notch. Clenching still matters, though, because it can affect how long a filling lasts.

How it differs from decay

Decay is caused by acid from bacteria in plaque, and it softens the tooth. The surface of a notch that is not decay, by contrast, is usually hard, smooth and shiny. A yellowish colour does not mean decay: the dentine beneath the enamel is naturally yellow, and that is the tissue the notch exposes. Your dentist touches the surface lightly with a fine instrument to check its hardness and colour and whether it holds plaque. The two can also occur in the same place: because the root surface is softer than enamel, decay can start at the edge of a notch on a tooth where the gum has receded.

A notch can also be sensitive: very fine channels in the exposed dentine lead towards the nerve, and cold, sweet food or the brush can set off a short, sharp twinge. How strong it is does not always match the depth; a deep hollow may not twinge at all, while a shallow one can be clearly sensitive.

Filling or monitoring

Not every notch is filled. A shallow notch that is not sensitive and not growing is often simply monitored; these notches usually progress slowly over years. Your dentist can record the notch with a photo or an intraoral scan and compare it at later check-ups. A filling is usually discussed when:

• Sensitivity continues despite a sensitivity toothpaste or a varnish applied at the practice.
• The notch is deepening and weakening the neck of the tooth, or getting close to the nerve.
• The hollow traps plaque and food and is becoming hard to keep clean.
• Decay has started in the notch, or you are unhappy with how it looks.

The filling is usually a tooth-coloured material bonded to the tooth: composite resin or glass ionomer.

Why a filling sometimes comes out

Fillings at the neck of the tooth come out more often than fillings on its other surfaces. Their edges sit very close to the gum, which makes it hard to keep the area dry during treatment, and because there is little enamel here, the filling bonds mostly to dentine. In a meta-analysis of how well these fillings stay in place, they were lost more often on teeth with wear facets from clenching or grinding, and held better on front teeth; the certainty of the evidence ranged from moderate to low.

Stopping the cause

Lost tooth tissue does not grow back, but progression can often be slowed. A European consensus report on acid wear also stresses that fillings are placed to ease pain and sensitivity and to restore appearance and function, but only alongside preventive steps.

• Use a soft-bristled brush, do not press, and use small movements from the gum towards the tooth instead of scrubbing sideways.
• Ask your dentist how abrasive your toothpaste is; some whitening toothpastes are more abrasive than others.
• Have acidic drinks with meals and finish them quickly rather than sipping them throughout the day.
• If you have reflux or vomit often, mention it at your check-up; it needs treatment beyond the teeth as well.
• If you grind your teeth at night, talk to your dentist about a night guard.

This content is for general information only and does not replace an examination.