Sensitive teeth, and when to worry about it

Under the enamel sits dentine, and dentine is threaded with microscopic tubules running toward the nerve. When enamel wears through or the gum recedes and exposes root surface, those tubules are open. Cold, sweet or touch causes fluid movement inside them, and the nerve reads that as a sharp jolt.

Sharp, immediate, gone within seconds of removing the cold — typically exposed dentine. Uncomfortable, manageable, worth mentioning at your next visit.

Lingering — the ache continues for thirty seconds or more after the stimulus is gone, or heat sets it off, or it wakes you at night. That pattern points at the nerve inside the tooth rather than the surface, and it should be looked at rather than managed at home.

• Gum recession exposing root surface, which has no enamel over it.
• Brushing too hard, or with a hard brush, wearing a notch at the neck of the tooth.
• Grinding or clenching, which flattens and cracks the biting surfaces.
• Acid erosion — diet, reflux, or frequent vomiting.
• Short-lived sensitivity after a new filling or after whitening, which usually settles.
• A cracked tooth, which classically hurts on releasing a bite rather than making one.

Desensitising toothpaste works, but slowly — give it several weeks, and smear a little on the sensitive spot with a fingertip at night rather than rinsing it away. Switch to a soft brush and ease off the pressure. Cut the frequency of acidic drinks rather than only the quantity; it is the number of acid attacks a day that does the damage.

If it is getting worse, is confined to one tooth, or lingers, that is the point to stop self-treating and have it looked at. A single tooth behaving differently from its neighbours is always more significant than general sensitivity across the mouth.