Why Are My Teeth Suddenly Sensitive?

Sudden sensitivity across several teeth is usually exposed dentine, from receding gums or worn enamel. Sudden sensitivity in one tooth is a different problem and more likely a crack, a failing filling or an inflamed nerve. Which pattern you have tells you how urgent it is.

Several Teeth or One Tooth?

This is the first thing to work out, because the two point in completely different directions.

Several teeth, usually along the gumline, sharp with cold, gone in seconds. This is exposed dentine. Something has removed the protective layer, either enamel from the outside or gum from the neck of the tooth. It is common, it is manageable, and it is rarely urgent.

One tooth, and it lingers. If a single tooth reacts and the ache carries on for thirty seconds or more after the cold has gone, that is a nerve becoming inflamed. It needs looking at rather than a change of toothpaste.

One tooth, sharp only when you bite down. That points to a crack or a failing filling rather than sensitivity at all. Covered in our guide to cracked teeth.

Why Teeth Become Sensitive at All

Under your enamel sits dentine, and running through it are thousands of microscopic tubules leading to the nerve. Enamel seals them. Gum covers the neck of the tooth where enamel is thinnest.

Remove either and those tubules are open to the world. Cold, heat, sweetness and air travel down them and reach the nerve directly. That is what sensitivity is: not damage exactly, but a lost seal.

It also explains why sensitivity often appears suddenly for something that developed slowly. Enamel wears gradually, then one day the last of the covering over a particular spot goes.

The Common Causes

Receding gums

The most frequent reason for sensitivity along the gumline. As gum pulls back, it exposes root surface that was never designed to be uncovered, and root has no enamel on it at all.

Caused by gum disease, by brushing too hard, and to some extent by age. You may be able to see it: the tooth looks longer, or there is a notch at the gumline you can catch with a fingernail.

Brushing too hard

The single most common self-inflicted cause, and almost everyone who does it thinks they are cleaning well.

Hard bristles and pressure wear a groove into the neck of the tooth and push the gum back at the same time. Scrubbing horizontally is worse than small circular movements. If your toothbrush bristles splay out within a few weeks, you are pressing too hard.

Acid erosion

Acid softens and dissolves enamel. The usual sources are fizzy drinks including sparkling water, citrus, fruit juice, wine, and vinegar-based dressings. Less obviously: reflux, frequent vomiting, and some medications that dry the mouth.

The timing matters more than the amount. Sipping something acidic over an hour does far more damage than drinking it in five minutes, because the acid attack is continuous.

Grinding and clenching

Grinding flattens the biting surfaces and flexes the tooth at the neck, which cracks off tiny flakes of enamel there. Many people have no idea they do it. Clues are an aching jaw in the morning, headaches at the temples, or a partner mentioning the noise.

After dental treatment

Sensitivity for a few days to a couple of weeks after a filling, a crown, or a scale and polish is normal and settles. Sensitivity after whitening is very common and temporary. Our page on what to expect after a filling covers the normal range.

A cavity or a failing filling

Decay reaching dentine causes sensitivity, and an old filling with a gap at the edge lets everything straight in. Both need treating rather than managing.

What Actually Helps

Things worth doing yourself

Switch to a sensitive toothpaste and use it properly. Most people rinse it away immediately, which wastes it. Brush with it, spit, and do not rinse. Better still, rub a little onto the sensitive spot with a fingertip at bedtime and leave it. Give it two to four weeks before judging it.

Change how you brush, not just what with. A soft brush, held lightly, small circles, angled towards the gum rather than scrubbing sideways. An electric brush with a pressure sensor is genuinely useful if you know you press hard.

Do not brush straight after anything acidic. Enamel is temporarily softened for around an hour afterwards, and brushing then scrubs it away. Rinse with water and wait.

Use a straw for acidic and cold drinks, and stop sipping them over long periods.

Wait a while before whitening again if that triggered it.

What a dentist can do

Fluoride varnish, painted onto the sensitive areas, which strengthens the surface and blocks the tubules. Quick, and often noticeably effective.

Bonding over exposed root surface. Where recession has left a notch at the gumline, filling it with tooth-coloured composite seals it physically. This is the most reliable fix for gumline sensitivity.

Treating the gum disease if recession is being driven by it. Sensitivity is a symptom there, and deep cleaning below the gumline addresses the cause.

A night guard if grinding is the driver.

Treating the cavity, filling or crack where one is responsible.

A gum graft, occasionally, for severe recession where tissue is taken from elsewhere in the mouth to cover exposed root. A bigger procedure, and rarely the first suggestion.

When Sensitivity Is Not Sensitivity

Some things get called sensitivity that are not, and treating them with special toothpaste wastes months.

Lingering pain after cold, throbbing on for a minute or more. Inflamed nerve, and it may need root canal treatment.

Pain that wakes you at night or comes on with no trigger at all. Not sensitivity.

Sharp pain only on biting, particularly on release. Cracked tooth.

Pain with swelling, a bad taste or a fever. Infection, and it needs an appointment now. Our guide to severe tooth pain covers what to do.

Sensitivity getting steadily worse over weeks despite doing the right things.

Frequently Asked Questions

Why have my teeth suddenly become sensitive?

Usually because dentine has become exposed, through gum recession or enamel wear that built up gradually and reached a threshold. Sudden sensitivity in a single tooth is more likely a crack, a cavity or an inflamed nerve.

Will sensitive teeth get better on their own?

Sensitivity from recent treatment or whitening usually settles within days or weeks. Sensitivity from recession or erosion does not, because neither reverses. It can be managed well, and the underlying wear needs addressing.

How long does sensitive toothpaste take to work?

Two to four weeks of consistent use. Do not rinse after brushing, and rubbing a little directly onto the area at bedtime works better than brushing alone.

Can receding gums grow back?

No. Gum tissue does not regenerate over exposed root. The recession can be stopped from worsening, the exposed area can be sealed with bonding, and severe cases can be covered with a graft.

Is tooth sensitivity a sign of decay?

Sometimes. Decay reaching dentine causes sensitivity, but so do several harmless things. Sensitivity in one tooth that lingers is more suspicious than mild sensitivity across several.

Why are my teeth sensitive to cold air?

Air moving over exposed dentine has the same effect as cold water. It usually means gumline exposure rather than anything in the biting surface.

Can whitening cause permanent sensitivity?

No. Whitening sensitivity is temporary, typically settling within a few days of finishing. If it persists beyond a couple of weeks, something else is going on.

Should I stop brushing a sensitive tooth?

No, and this is important. Plaque left on an exposed root surface causes decay quickly, because root has no enamel. Brush it gently with a soft brush rather than avoiding it.

Get It Diagnosed in Elephant & Castle

Sensitivity is worth an examination mainly to rule out the things that are not sensitivity. If it turns out to be exposed dentine, fluoride varnish or bonding usually deals with it quickly.

Call 020 7928 4474 or book online. We are in Elephant and Castle, minutes from Waterloo, Borough and London Bridge. Our hygiene page covers what a routine visit includes.

This page is general information, not a diagnosis. Last reviewed August 2026.