Tooth sensitivity is a short, sharp pain when a tooth meets cold, heat, sweetness, acid, or air. It happens when the dentin underneath the enamel loses its covering, either because enamel has worn away or because the gum has receded and exposed the root. Dentin is full of microscopic tubules running to the nerve, so a stimulus at the surface is felt almost instantly. Most cases respond to a desensitising toothpaste and a change in brushing habits within two to four weeks. Pain that lingers after the stimulus is gone, or that wakes you at night, is a different problem and needs a dentist.
What is actually happening in the tooth
A tooth has three layers. Enamel on the outside is the hardest substance in the body and has no nerve supply. Underneath sits dentin, which is softer and riddled with thousands of microscopic channels called tubules, each running inward toward the pulp where the nerve lives. The pulp is the only part that can feel.
When dentin is covered, by enamel on the crown or by gum and cementum on the root, nothing much reaches those tubules. When it is exposed, fluid inside the tubules moves rapidly in response to temperature changes, pressure, or osmotic shifts from sugar and acid. That fluid movement tugs on nerve endings at the inner end of the tubule, and the brain reads it as a sharp, brief pain. This is called the hydrodynamic theory, and it explains why sensitivity is instant and why it stops the moment the stimulus is removed.
The common causes
Brushing too hard, or with a hard-bristled brush. The single most common cause in practice. Aggressive horizontal scrubbing wears a notch into the tooth at the gum line and pushes the gum back, exposing root dentin, which has no enamel at all. Our brushing guide covers the pressure and angle that avoid this.
Receding gums. From hard brushing, gum disease, grinding, or simply age. Exposed root surface is far more sensitive than the crown. See our guide to receding gums.
Acid erosion. Citrus, soda, sports drinks, wine, and reflux all dissolve enamel over time. Erosion is usually diffuse rather than a single spot, and often affects several teeth at once.
Grinding or clenching. Flexing a tooth under heavy load fractures enamel at the gum line and wears the biting surfaces. Sensitivity from teeth grinding often comes with jaw soreness in the morning.
A cracked tooth. Pain on biting and releasing, usually on one specific tooth, often worse with cold. Cracks can be invisible on an X-ray.
Tooth decay. A cavity that has reached dentin causes sensitivity to sweet things first, then cold (see early signs of a cavity). Our guide to what a cavity looks like covers the visual signs.
A failing or recent filling. New fillings are often sensitive for a few weeks; a filling with a gap underneath lets stimuli through indefinitely.
After whitening. Peroxide temporarily opens the tubules. Very common, harmless, and resolves within a few days of stopping. See teeth whitening sensitivity.
After a cleaning or deep cleaning. Removing tartar exposes root surfaces that were covered. Settles within a week or two.
Sensitivity or something worse? How to tell
This distinction matters more than anything else on this page.
| Sensitivity (dentin hypersensitivity) | Pulp inflammation (pulpitis) | |
|---|---|---|
| Pain duration | Seconds; stops when the stimulus goes | Lingers 30 seconds to many minutes |
| Trigger | Cold, sweet, acid, air | Cold and especially heat; may come with no trigger at all |
| At night | No | Often worse lying down; may wake you |
| Location | Often several teeth, or a general area | Usually one tooth, which you can eventually point to |
| Painkillers | Not usually needed | Often needed, and may not fully work |
| Outcome | Managed at home | Needs treatment, often a root canal |
If heat sets it off, if the pain lingers, or if it throbs on its own, stop treating it as sensitivity and book an appointment. The nerve is inflamed, and that does not resolve by itself.
What actually works
Desensitising toothpaste. The first-line treatment and effective for most people. Two active ingredients have good evidence: potassium nitrate, which calms the nerve ending, and stannous fluoride, which physically plugs the tubules. Use it twice a day, and for a faster result rub a small amount directly onto the sensitive area with a fingertip at bedtime and do not rinse. Give it a full two to four weeks before judging; the effect is cumulative, and stopping early is the most common reason people think it failed.
Change how you brush. Soft bristles only, light pressure, small strokes angled into the gum line rather than scrubbing across. An electric brush with a pressure sensor is genuinely useful here, because the most common cause is pressure people do not realise they are applying. Our electric toothbrush guide explains what to look for.
Wait after acid. Do not brush for 30 to 60 minutes after citrus, soda, wine, or vomiting; enamel is temporarily softened and brushing scrubs it away. Rinse with water instead.
A fluoride mouth rinse at a different time of day from brushing adds protection for people with ongoing erosion.
In the dental office, if home measures fail: a fluoride varnish applied to the sensitive spots, a bonded resin or filling to seal an exposed notch, a desensitising agent painted onto the root, a night guard if grinding is the driver, or a gum graft to recover the covering on a badly receded root. For a tooth where the nerve is already inflamed, a root canal is the definitive answer.
What does not work: charcoal and other abrasive “whitening” powders, which make erosion worse; cutting out all cold food, which treats the symptom and lets the cause continue; and switching to a harder brush, which is the exact opposite of what is needed.
Preventing it coming back
Most sensitivity is a wear problem, and wear is cumulative. Soft brush, light hand, fluoride toothpaste twice a day, keep acidic drinks to mealtimes and use a straw, treat grinding with a guard rather than ignoring it, and keep up six-monthly check-ups so recession and erosion are caught while they are small. If you whiten, space out the courses and use a sensitivity toothpaste for two weeks beforehand.
When to see a dentist
Book an appointment if sensitivity has not improved after four weeks of twice-daily desensitising toothpaste; if it is confined to one tooth; if pain lingers for more than 30 seconds after the trigger is removed; if hot drinks set it off; if pain appears on its own, throbs, or wakes you at night; if biting down on something hard produces a sharp pain, which suggests a crack; or if you can see a notch, a dark spot, a chip, or gum that has visibly pulled back. Treat facial swelling, fever, or a bad taste as urgent and see a dentist the same day, since that combination points to infection rather than sensitivity. Our guide to tooth abscess covers those warning signs.
Frequently asked questions
Why are my teeth suddenly sensitive?
A sudden change usually has a specific trigger: a recent whitening course, a new filling, a dental cleaning, a change of toothbrush, a period of grinding during stress, or a crack. If nothing obvious changed and it is confined to one tooth, have it checked rather than waiting.
How long does tooth sensitivity last?
Sensitivity after whitening or a cleaning usually settles within a few days to two weeks. Sensitivity from exposed dentin improves over two to four weeks of desensitising toothpaste but returns if the cause, usually hard brushing, continues.
Does sensitive toothpaste really work?
Yes for most people, with the caveat that it is cumulative. Potassium nitrate and stannous fluoride both have solid evidence, but they need twice-daily use for several weeks. Rubbing a little onto the sensitive spot at night and not rinsing speeds it up.
Can sensitive teeth be a sign of a cavity?
They can. Decay that has reached dentin typically causes sensitivity to sweet things, then to cold. A cavity usually affects one tooth and often has a visible dark spot or a catch you can feel with your tongue. Generalised sensitivity across several teeth is more often wear or recession.
Is tooth sensitivity permanent?
Not usually. The exposed dentin does not grow enamel back, but the tubules can be blocked and the nerve response calmed, so the symptom resolves. Where the cause is a deep notch or severe recession, a dentist can restore the covering with bonding or a graft.
