Sensitive teeth

What happens in a sensitive tooth

The crown of a tooth is covered by enamel, and the root, below the gum, by a thin layer called cementum. Beneath both lies dentine, which is threaded with microscopic tubules that lead towards the nerve in the centre of the tooth.

While enamel and gum cover it, dentine is protected. Where the enamel wears away or the gum shrinks back, the tubules are left open. Cold, heat, sweetness or acid can then reach the nerve through them and cause a brief, sharp pain. The medical name for this is dentine hypersensitivity.

How it feels

Typically, the pain is sharp and short. It is set off by something cold, hot, sweet or acidic, by cold air, or by brushing, and it fades soon after the trigger is gone. It often affects several teeth, usually near the gum line, where roots are most likely to be exposed.

Common causes

• brushing too hard, or with a hard-bristled brush;
• gums that have receded, which becomes more common with age and after gum disease;
• acid wear of the enamel from fizzy drinks, fruit juices, citrus fruit or stomach acid, for example with reflux;
• grinding or clenching the teeth;
• tooth whitening, which usually causes temporary sensitivity;
• recent dental work, such as a new filling or a professional clean.

When it may be something else

Pain from exposed dentine is brief and comes with a trigger. Other problems can feel similar at first, including decay, a cracked tooth, a worn or leaking filling, gum disease or an inflamed nerve (pulp). See a dentist if:

• the pain is severe, or has come on suddenly;
• only one tooth is affected;
• the pain lingers after the cold or heat has gone, throbs, or wakes you at night;
• it hurts to bite;
• sensitivity lasts more than a few weeks despite a sensitive toothpaste.

Swelling of the gum or face, or a bad taste with pain, can mean infection. The guide to dental emergencies explains when this is urgent.

What helps at home

1. A desensitising toothpaste. Pastes containing potassium nitrate, potassium citrate or stannous fluoride work by blocking the open tubules or by damping the signal they carry to the nerve. Use one twice a day, every day: the effect builds up with regular use and fades if you stop. At night, a little can also be rubbed onto the sensitive area and left there.

2. Spit, don't rinse. After brushing, spit out the toothpaste without rinsing with water, so that the active ingredients and the fluoride stay on the teeth.

3. A soft brush and a light touch. Brush gently in small movements rather than scrubbing across the gum line.

4. Fewer acid attacks. Cut down how often you have acidic food and drink, and keep them to mealtimes. Avoid sipping acidic drinks slowly over a long time or holding them in the mouth. Water and milk are the kindest drinks between meals.

Advice differs on brushing after acidic food or drink. The Oral Health Foundation advises waiting at least an hour before brushing. The UK's Delivering better oral health finds no strong evidence that the timing matters much, and puts the weight instead on how often acidic food and drink are taken.

What a dentist can do

The dentist first looks for the cause, since treating it may be enough. Depending on what is found, options include:

• a desensitising varnish or fluoride gel painted onto the exposed areas;
• a toothpaste with a higher level of fluoride;
• a sealant, a bonded filling or, in some cases, a crown or inlay to cover worn areas near the gum line or repair a flaw in the tooth;
• treatment of gum disease and, where gum has been lost from the root, sometimes a gum graft;
• a night guard for grinding;
• root canal treatment, when sensitivity is severe and persistent and other measures have not helped.

Exposed roots are often linked to receding gums and gum disease. Pain that lingers can signal an inflamed pulp, which is explained on the page about root canal treatment.