A glass of water and soft toothbrush on a bathroom shelf

Quick answer

Tooth sensitivity happens when the protective enamel or gum coverage thins, exposing the microscopic tubes that run to the nerve. Common causes: overenthusiastic brushing, gum recession, acid wear from diet or reflux, grinding, and early decay. Sensitivity toothpaste used correctly (twice daily, spit don't rinse, dabbed on the worst spots at night) genuinely works for simple cases within a few weeks. Sensitivity that's localised to one tooth, lingers after the trigger, or appeared suddenly needs an examination, because those patterns point to decay, a crack, or a dying nerve.

The mechanism, in one paragraph

Under the enamel, tooth structure is threaded with microscopic fluid-filled tubes that run to the nerve. When enamel thins or gums recede, cold, sweet and touch move that fluid, and the nerve reads movement as a zing. Everything that follows is about covering those tubes back up or calming the nerve behind them.

The usual causes

  • Brushing too hard. Enamel and gums both retreat under a scrubbing action and a hard brush. The fix is technique, not less brushing.
  • Gum recession. Exposed root surfaces have no enamel at all, so they feel everything. See our gum health guide for the disease version.
  • Acid wear. Citrus, soft drinks, sports drinks and reflux all dissolve enamel a little at a time. Rinse with water after acids and wait 30 minutes before brushing, because brushing softened enamel scrubs it away.
  • Grinding and clenching. Flexing teeth under load opens the tubes; grinders often wake with sensitive, tired teeth. That's a grinding problem wearing a sensitivity mask.
  • Whitening. Temporary sensitivity is common mid-treatment and manageable; see the whitening guide.
  • Early decay or a leaking filling. The cause that toothpaste can't fix, and the reason one-tooth sensitivity earns an X-ray.

Home treatment that actually works

  • Sensitivity toothpaste twice daily, every day; it builds protection over weeks, not doses
  • Spit, don't rinse, so the active ingredient stays on the teeth
  • At night, dab a smear directly on the worst teeth and leave it
  • Soft brush, gentle circles, 45 degrees to the gumline
  • Keep acids to mealtimes and rinse with water afterwards
Give the toothpaste routine three to four weeks of honest effort. Generalised, mild sensitivity usually improves. If it doesn't, or if one tooth stands out, stop treating blind and let us look.

When the dentist earns their keep

Sensitivity that is new, one-sided, lingering, or worsening gets an examination and usually an X-ray. In the chair we can seal exposed root surfaces with desensitising varnish or bonding, repair the decay or cracked filling that was masquerading as sensitivity, and fit a night splint where grinding is the engine. The fix that matches the cause is the one that lasts.