Post-whitening tooth sensitivity: normal or a warning sign?

The sensitivity that appears after teeth whitening is almost always described in the same way: a “shock,” a sudden chill from cold air, water, or even a simple touch. For some people, it lasts for minutes; for others, it accompanies the day like a small electric current that appears without warning. It is not pleasant, but it does not mean that something has gone wrong. Post-whitening sensitivity has a clear biological explanation, limits that deserve attention, and ways to prevent or reduce it without compromising the result. This is where the difference between “normal” and “warning sign” becomes essential.

Why does whitening cause sensitivity?

During teeth whitening, agents such as hydrogen peroxide or carbamide peroxide penetrate through the enamel to reach the dentin, where accumulated pigments are found. This process occurs by diffusion and is entirely expected. What we know today is that the released molecules can stimulate fluids within the dentinal tubules, activating nerve fibers and creating a transient response, similar to the sensitivity caused by acid wear or overly vigorous brushing.

Clinical studies show that sensitivity is the most common complaint in whitening, with a prevalence between 55% and 75% of patients, varying according to the concentration of the agent and the application time. The good news is that in most cases, the discomfort is temporary and subsides spontaneously within 24 to 72 hours. The mechanism is irritative, not destructive; it does not cause permanent damage to the tooth structure.

What is considered “normal” sensitivity after whitening?

Not all sensitivity is the same, and it is important to understand the limits of what is expected. There is a typical, benign pattern:
• It arises during the session or within the following 12 hours
• It is triggered by cold, sweets, or air
• It is short-lived, lasting only a few seconds
• It improves with simple painkillers
• It gradually diminishes over one to three days

This type of sensitivity is associated with the whitening mechanism itself: temporary opening of the dentinal tubules and increased nerve response. It does not alter the enamel, does not “wear down” the tooth, and does not compromise the result.

There are factors that increase the likelihood of experiencing it: gum recession, cervical abrasion, thin enamel, history of previous sensitivity, frequent exposure to acids, or hard brushing. In these cases, the protocol should be adjusted before starting treatment.

When sensitivity is no longer normal

There are situations that require clinical attention because they point to a cause other than whitening:
• Pain that does not subside after 72–96 hours
• Constant spontaneous sensitivity, not just provoked
• Pulsating or prolonged pain after cold (may indicate pulp inflammation)
• Sensitivity localized to a single tooth, always in the same spot
• Pain when chewing or percussion (may be a crack, deep caries, or structural lesion)

These signs are not typical of bleaching and should be evaluated to rule out pulp pathology or pre-existing lesions that the patient was unaware of. Bleaching does not cause caries or fractures, but it can “reveal” symptoms in a tooth that already had structural vulnerability.