What causes sensitive teeth?
Something has exposed the layer underneath your enamel. The useful question is what — and whether the pain is the ordinary kind or the kind that needs seeing to this week.
Healthy enamel feels nothing. It has no nerve supply, which is why you can bite something frozen and, if everything is intact, register only cold. Sensitivity means the layer beneath it — dentine — is exposed somewhere, and dentine is a different material entirely.
The mechanism, briefly
Dentine is not solid. It is threaded with millions of microscopic channels called tubules, running from its outer surface inward toward the pulp, where the nerve lives. Those tubules are full of fluid.
When exposed dentine meets something cold, sweet or simply a toothbrush, that fluid moves. The nerve endings at the inner end of the tubules detect the movement and report it as a short, sharp pain. That is the whole of it — the tooth is not damaged by the cold drink, it is reporting a pressure change through a channel that should have been covered.
This is why sensitivity is sharp and brief rather than dull and lingering. It is also why it comes and goes: what matters is whether the tubules are open.
What exposes dentine
| Cause | What it looks like | What helps |
|---|---|---|
| Receding gums | Sensitivity at the gumline; teeth look longer; a notch you can feel with a fingernail | Stop the recession first — see what causes receding gums |
| Acid erosion | Generalised, often worse on the inside surfaces; teeth look glassy or thin at the edges | Cut acid frequency; do not brush for 30 minutes after |
| Abrasion from brushing | Wedge-shaped notches at the gumline, often worse on one side | Soft brush, light pressure, pen grip |
| Recent whitening | Started with treatment, affects many teeth at once, fades over days | Pause; it is usually temporary and reversible |
| A new filling or crown | One tooth, began after the appointment | Usually settles in a few weeks; tell the dentist if it does not |
| Grinding | Flattened biting surfaces, jaw ache on waking | A night guard; treat the grinding, not just the symptom |
| Decay or a crack | One tooth, getting worse, may hurt on biting | A dentist. This is not ordinary sensitivity |
The distinction that actually matters
Ordinary sensitivity is sharp and stops within a second or two of the cold going away. That is a tubule problem and it is manageable.
Pain that lingers for thirty seconds or more after the stimulus, arrives unprovoked, wakes you at night, or hurts when you bite down is a different thing. That pattern suggests the nerve itself is inflamed or the tooth is cracked, and no toothpaste addresses either. Book an appointment rather than waiting it out — this is the one part of this page worth acting on today.
What sensitivity toothpaste actually does
There are two mechanisms on the shelf, and they work differently.
- Potassium nitrate calms the nerve itself, making it less reactive to the fluid movement. It does not seal anything.
- Stannous fluoride, arginine and similar physically block the open ends of the tubules. They also deposit fluoride, which is useful in its own right on exposed root.
Both need two to four weeks of consistent use. This is the single most common reason people conclude sensitivity toothpaste does not work — they try it for four days. Use it as your ordinary toothpaste, twice daily, and judge it at the end of the month.
One trick worth knowing: after brushing, smear a little onto the sensitive spot with a fingertip and leave it rather than rinsing. And do not rinse after brushing generally — see is mouthwash bad for you? for why that habit undoes your fluoride.
What makes it worse
- Brushing straight after anything acidic Acid softens the surface temporarily. Brushing then scrubs away mineral you would otherwise have recovered. Rinse with water and wait half an hour.
- Pressure Hard bristles and a firm grip abrade the exact area that is already thin. If your brush splays within a month, that is your answer.
- Repeated whitening Peroxide opens tubules temporarily. Occasional use is fine; back-to-back courses are not. See natural teeth whitening for what actually works.
- Ignoring a dry mouth Less saliva means less remineralisation and more acid sitting around — dry mouth makes everything on this page worse.
See a dentist if
The pain lingers, wakes you, or comes without a trigger; one tooth is clearly worse than the rest; it hurts to bite; there is swelling; or a month of sensitivity toothpaste used properly has changed nothing. Sensitivity is common and usually benign, but it is also how a cracked tooth and an inflamed nerve announce themselves, and those get more expensive the longer they wait.