Whitening without the pain: sensitive teeth and enamel

Quick answer Whitening sensitivity happens when peroxide passes through enamel and irritates the tooth's nerve; it usually fades within a few days of stopping. Brush with a potassium nitrate or stannous fluoride toothpaste for 2 weeks before and during whitening, choose a lower strength and take breaks between sessions.

Why whitening makes teeth twinge

Under your enamel is dentin, a layer full of tiny tubes that lead to the tooth's nerve. Peroxide travels through enamel into dentin and can irritate the nerve for a while. The result is a short, sharp twinge with cold air or cold drinks, often in the first days of treatment.

Sensitivity is the most common side effect of whitening. It's usually mild and temporary, often settling within 1–3 days after you pause or finish. It's more likely when:

• the peroxide is stronger (in-office gels, high-percentage strips)
• the product stays on longer than directed
• trays fit poorly and gel leaks onto the gums
• you already have sensitive teeth, receding gums or worn enamel

Prepare your teeth before you start

• Switch toothpaste 2 weeks ahead. Desensitizing toothpastes need several uses to work. Potassium nitrate calms the nerve, while stannous fluoride and arginine help seal the open tubes in dentin. Keep using it twice a day while you whiten.
• Fix problems first. Cavities, cracked fillings and gum disease make whitening painful, so have a checkup before you begin.
• Use a soft brush and light pressure so you don't wear enamel or push back your gums. See how to brush your teeth properly.

Pace your whitening

• Start low. If you're prone to sensitivity, choose 10% carbamide peroxide or a low-strength strip rather than the strongest product. Compare them in every whitening option.
• Shorten sessions. Use the shortest time on the label, or wear trays for 1–2 hours instead of overnight.
• Skip days. Whiten every other day, or take a 2–3 day break as soon as teeth start to twinge. The final shade is usually the same; it just takes longer.
• Ask about a desensitizing gel. Dentists can supply a potassium nitrate and fluoride gel to wear in your trays for a short time before or after whitening.
• Go easy on very hot or very cold food and drinks for a few hours after each session.
• Stop and see a dentist if pain is severe, throbbing or still there after a few days off.

Is whitening safe for enamel?

Used as directed, peroxide whitening doesn't dissolve enamel. Lab studies show that very strong or very frequent bleaching can roughen the surface slightly, and overuse can harm enamel and gums. That's why it pays to follow label times, leave several months between full courses and keep using a fluoride toothpaste, which helps keep enamel strong. Acidic home remedies such as lemon juice or vinegar do erode enamel, so skip them.

Other causes of sensitive teeth

Not all sensitivity comes from whitening. Roughly 1 in 9 dental patients has sensitive teeth. Common causes include:

• Worn enamel from acidic drinks (soda, sports drinks, citrus), grinding or brushing too hard
• Gum recession, which exposes the root surface; roots have no enamel
• Cavities, cracked teeth or worn fillings
• Gum disease; see gum health
• Recent dental work such as a filling or a deep cleaning, which usually settles on its own

To protect your teeth, wait about 60 minutes after acidic food or drink before brushing, sip acidic drinks instead of swishing them, wear a night guard if you grind, and use a toothpaste made for sensitivity (see how to choose a toothpaste). Dabbing a little on a sore spot before bed can also help.