Teeth whitening sensitivity: why it happens and how long

Why the sharp zings happen

Whitening sensitivity is a short, sharp shock lasting a second or two, and it comes from peroxide passing through enamel into the dentinal tubules and reaching the nerve, producing a brief and reversible inflammation of the pulp. It is not damage. It typically starts a few hours after the session, peaks within the first twenty-four hours and settles within forty-eight to seventy-two. Many patients notice nothing at all, and most of those who do describe it as annoying rather than painful.

What we do before the gel goes on

Sensitivity is largely predictable, which means it is largely preventable. We check for exposed root surfaces, cracks, leaking old fillings and untreated decay first, because those are the teeth that hurt afterwards, and each of them is treated before whitening is booked at all. Patients who already report cold sensitivity start a potassium nitrate desensitising toothpaste two weeks before the appointment, and a fluoride varnish goes on immediately after the last gel application.

The forty-eight hours that decide your experience

Avoid ice, very cold drinks and anything scalding for two days; the tubules are temporarily open and thermal stimuli travel straight down them. Skip whitening and combined sensitivity-whitening toothpastes during this window and use a plain fluoride paste instead. A standard anti-inflammatory painkiller taken an hour before the session lowers the peak for patients who have had trouble previously. Do not stack a second session onto the following day to chase a brighter shade.

When sensitivity means something else

There is one pattern we ask you to report. Generalised sensitivity that fades over two or three days is normal bleaching behaviour. Pain localised to a single tooth, lingering more than thirty seconds after cold, or still present a week later is not caused by the whitening. It is a crack or an inflamed nerve that the peroxide has revealed. That tooth needs assessment, and root canal treatment starts at €120 if the pulp is involved.

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