Why is my tooth sensitive to cold?
Short answer: A short, sharp zing that stops as soon as the cold is gone usually means exposed root surface or worn enamel, and is manageable. Pain that lingers for thirty seconds or more after the cold has gone suggests the nerve inside the tooth is inflamed, which is a different problem and needs seeing promptly.
The one thing worth timing
Sensitivity is common and mostly harmless. The distinction that actually matters is how long it lasts once the cold is removed.
A few seconds. Fluid movement in exposed dentine tubules. Cause is usually gum recession exposing root, enamel worn thin, or a recently placed filling settling. Treatable and not alarming.
Thirty seconds or more, or a throb that builds. This suggests irreversible inflammation of the nerve — the pulp. It does not settle by itself and usually ends in root canal treatment or extraction. Booked promptly, it is far more comfortable than left.
Time it once with a cold drink before you call. It is the single most useful thing you can report.
Why it happens
- Gum recession. Exposed root has no enamel, so cold reaches the nerve far more directly. See can receding gums grow back?
- Enamel wear. From acidic diet, reflux, or brushing hard with an abrasive paste.
- Grinding. Wears enamel and flexes the tooth at the neck. See grinding at night.
- A crack. Especially if there is also pain on biting.
- Decay reaching the dentine.
- Recent whitening. Common, temporary, and settles within days.
What helps
Use a desensitising toothpaste properly: it needs weeks of consistent use, and rubbing a little onto the sensitive spot with a fingertip at night, without rinsing after, works better than brushing and spitting.
Switch to a soft brush and stop scrubbing — hard brushing is a leading cause of the recession that causes the sensitivity in the first place. Give acidic drinks a rest, and do not brush for an hour after them, because enamel is temporarily softened.
In the chair, fluoride varnish, a bonded covering over an exposed root, or treating the underlying crack or decay all help depending on the cause.
Common questions
How long should cold sensitivity last?
A few seconds. If pain lingers for thirty seconds or more after the cold is gone, or builds into a throb, the nerve is likely inflamed and you should be seen promptly.
Does sensitive toothpaste actually work?
Yes, for sensitivity caused by exposed dentine, but it takes several weeks of consistent use. Rubbing it onto the sensitive spot at night and not rinsing afterwards works better than ordinary brushing.
Why is one tooth suddenly very sensitive?
A single tooth changing suddenly is more concerning than general sensitivity. It suggests a crack, decay, a failing filling, or nerve inflammation, and should be examined.
Is sensitivity after whitening normal?
Yes. Temporary cold sensitivity is the most common side effect of whitening and typically settles within a few days of finishing. Tell your dentist if you already have sensitive teeth, because it changes how treatment is planned.