Why Teeth Become Sensitive, and What Actually Helps
Sensitivity · 26 August 2026 · 5 min read
Sensitivity usually means dentine, the layer beneath enamel, has become exposed — from enamel wear, a crack, gum recession, or a leaking filling. Desensitising toothpaste can mask mild cases, but it does not treat the cause, so sensitivity that persists or is getting worse is worth having examined rather than managed indefinitely.
What sensitivity actually is
Enamel has no nerve endings of its own. Dentine, the layer underneath, is riddled with microscopic tubules that connect to the nerve at the centre of the tooth. When dentine is exposed — at the gum line, at a worn edge, or under a leaking filling — fluid movement in those tubules is what produces the sharp, brief sensation from cold, sweet or acidic things.
The common causes
Enamel wear from grinding or acid erosion is one of the most frequent causes, because it thins the enamel covering the dentine beneath. Gum recession is another: as the gum line moves, root surface that was never meant to be exposed is left bare, and root surface has no enamel over it at all. A crack or a filling with a failing margin can expose dentine at a single point, which is why sensitivity confined to one tooth is treated differently from sensitivity across many.
Why toothpaste alone often isn’t enough
Desensitising toothpaste works by blocking the tubules or calming the nerve response, and for mild, generalised sensitivity it genuinely helps. What it cannot do is fix a crack, rebuild worn enamel, or seal a leaking filling margin. Using it as the only response to sensitivity that is getting worse, or that sits in one specific tooth, usually just delays finding out what is actually causing it.
How a cause is found
A cracked tooth or an early lesion at the margin of a filling is not always visible to the eye. Near-infrared imaging can show a crack or early decay as a shadow, with no radiation, and a 3D scan taken at one visit can be compared with a later one to see whether recession or wear has actually progressed, rather than relying on memory.
What can help, depending on the cause
Exposed root surface from recession can be covered with a bonded resin. Sensitivity from grinding is addressed with a night guard and, where relevant, gum treatment if recession is active. Wear from acid erosion improves by removing the source and changing when brushing happens — not brushing for about half an hour after something acidic, since brushing softened enamel removes it. A cracked tooth or a failing filling margin needs the specific repair, not a coping strategy.
Questions
Is sensitivity always something serious?
No. Mild sensitivity to cold that comes and goes is common and often responds to a desensitising toothpaste. Sensitivity that is getting worse, is sharp rather than mild, or is confined to one tooth is more likely to have a specific cause worth finding.
Can whitening make teeth more sensitive?
Yes, temporarily, for some people. It usually settles within a few days of finishing treatment. Persistent sensitivity after whitening is worth mentioning at a review.
How long should I try toothpaste before seeing a dentist?
A couple of weeks of consistent use is a reasonable trial for mild, generalised sensitivity. If it has not improved, is getting worse, or is limited to one tooth, have it looked at rather than continuing to manage it.
Can sensitivity be reversed?
It depends on the cause. Exposed dentine from recession or wear can be covered with a bonded resin. Sensitivity from a crack or a leaking filling is resolved by treating that specific problem, not by managing the symptom indefinitely.