Tooth pain after whitening: why it happens and what helps

What’s probably going on

Most whitening products use peroxide to bleach the tooth. The peroxide doesn’t stay on the surface. It passes through the enamel into the softer layer underneath (dentin) and can reach the nerve, where it causes mild, short-lived inflammation. That’s the zing or ache you feel.

This is common. The American Dental Association says mild to moderate sensitivity can affect up to two-thirds of people early in a whitening treatment. It tends to be worse with:

• Stronger gels. Higher concentrations of peroxide cause more sensitivity.
• Longer contact. Leaving the gel or strips on longer, or using a whitening light for longer, adds up.

Sore gums are a separate thing

If your gums burn or feel sore where the gel touched them, that’s irritation of the gum tissue, not the tooth. It often comes from a tray that doesn’t fit well or gel that squeezes out onto the gums. Wipe away extra gel and keep it off your gums.

When it may not be the whitening

Whitening sensitivity tends to fade after you stop. Pain that stays in one tooth, or keeps going, deserves a closer look. It can mean something else is going on that whitening just brought to your attention:

• A cavity. Decay lets cold, sweets and bleach reach the nerve more easily.
• A cracked tooth. Sharp pain when you bite down or let go. See cracked tooth.
• A worn or leaky filling.
• Gum disease or an exposed root.

If one tooth hurts more than the rest, have a dentist check it before you whiten again.

How long it lasts

The ADA’s summary of the research says sensitivity can show up within two or three days of starting a whitening program and usually resolves by about the fourth day after treatment. Cleveland Clinic’s dentists say much the same: it’s common, and it tends to go away fairly quickly.

If sensitivity is still there several days after your last treatment, or it’s getting worse instead of better, see a dentist.

What to do tonight

1. Take a break from whitening. The ADA’s consumer site says you can delay the treatment and try again later.
2. Brush with a sensitivity toothpaste. It helps block the signal from the tooth surface to the nerve. It usually takes several brushings to work, so start now. See the best toothpaste for sensitive teeth.
3. Go easy on very cold or very hot food and drinks for a day or two. Lukewarm is often more comfortable while teeth are sensitive.
4. When you start again, go gentler. Cleveland Clinic suggests switching to a milder product. Research the ADA cites found that lower-strength peroxide caused less sensitivity and still whitened teeth well.

What not to do

• Don’t keep whitening through the pain, or leave gel on longer to finish faster.
• Don’t use more product, or use it more often, than the directions say. The ADA warns that overusing whiteners can damage enamel or gums.
• Don’t assume a sore single tooth is from the whitening. Get it checked.

How a dentist fixes it, and what it costs

For ordinary whitening sensitivity, there’s usually nothing to fix. It fades on its own once you stop.

If a dentist finds a different cause, the treatment matches the cause: a filling for a cavity, a new filling for a leaky old one, or often a crown for a cracked tooth. For stubborn sensitivity, a dentist can apply a fluoride gel or other in-office treatment. See tooth sensitive to cold for more on those options.

The price depends on the treatment, the tooth and your coverage, so ask for a written estimate first. If you don’t have dental insurance, a dental savings plan (a discount membership, not insurance) can lower the price at participating dentists. The dental cost estimator gives rough national ranges.

How to whiten more comfortably next time

• See a dentist before you start. Both the ADA and Cleveland Clinic recommend it. A dentist can spot cavities, cracks or gum problems first, and tell you whether whitening will even help. Brown teeth may not respond as well, and teeth with gray tones may not bleach at all.
• Know that crowns, veneers and fillings won’t whiten. Only natural teeth change color, so a front crown may no longer match.
• Start with a lower strength and shorter sessions. Build up only if your teeth are comfortable.
• Look for the ADA Seal of Acceptance on whitening products. It means the product was tested for safety and effectiveness.
• Tell your dentist if your teeth are already sensitive. They can help you pick a gentler approach.
• Stick to the directions. More isn’t better; overuse can harm enamel and gums.

A soft, gentle brush helps too. See the best electric toothbrush.