How long does teeth whitening last, and who should not have it?

Whitening breaks down the colour molecules within the tooth using peroxide-based gels. It does not abrade the surface, and when done under dental supervision it has not been shown to damage enamel. How long the result lasts depends on habits and on the type of discolouration.

Types of discolouration

Extrinsic (surface) stains come from tea, coffee, tobacco and coloured foods; scaling and polishing remove most of them. Intrinsic discolouration is due to age-related darkening of the dentine, trauma, root canal treatment or certain medicines; this is what whitening actually targets. Yellowish shades respond well; greyish and banded discolouration responds only partially.

In-office and at-home

In-office whitening applies a high-concentration gel in a single visit with the gums protected; results are fast. At-home whitening uses custom trays with a low-concentration gel for 1–2 weeks; sensitivity is lower and the patient is in control. A combined protocol using both is one of the most durable approaches.

How long it lasts

The shade achieved is usually kept for 1–3 years. Smoking, several cups of coffee/tea a day and red wine shorten it. A short annual top-up with the home trays is enough; more frequent use is not advised because of the sensitivity risk.

Sensitivity

Cold sensitivity during and for 1–2 days after treatment is common and temporary. Using a desensitising toothpaste beforehand and short cycles reduce it. Exposed dentine and decay are treated first; otherwise there will be pain.

Who should not have whitening?

• During pregnancy and breastfeeding
• Under age 16 (the pulp chamber is large)
• With untreated decay or gum disease
• With a peroxide allergy
• With many fillings or crowns in the front region — these will not lighten and a shade mismatch results; planning is done at the examination

Whitening toothpastes and strips

Toothpastes remove surface stains but do not lighten the tooth's shade. Over-the-counter strips are low-dose, touch the gums and give uneven results. A lasting shade change needs dentist-supervised treatment.

How many shades, and when is the result seen?

In-office treatment lightens 2–6 shades within the visit; for the first 24 hours the teeth look whiter than they are because of dehydration, and the true shade settles in 1–2 weeks. With home whitening the change is gradual and becomes obvious in 7–14 days. Yellow-brown tones respond better than grey.

To prolong the effect

• Dark drinks through a straw and with meals; rinse with water afterwards
• No smoking — the strongest stainer
• Brush twice a day and polish every 6 months
• A 2–3-night home top-up once a year (keep the trays)
• Limit acidic drinks: worn enamel looks more yellow

Does whitening damage teeth?

Whitening done under supervision, at the right dose and duration, has been shown not to cause permanent enamel damage. Temporary sensitivity and gum irritation are the commonest side effects, reduced by barriers and dose adjustment. Damage usually comes from unregulated products, too-frequent repetition and abrasive home remedies.

Where results are limited

• Tetracycline staining (grey bands): partial response with a long home protocol; veneers if marked
• Fluorosis: white spots may look more obvious after whitening; microabrasion/resin infiltration first
• Many fillings or crowns in the front region: mismatch after whitening; restorations are replaced
• Thin enamel and widespread wear: sensitivity risk, low dose and short sessions

Frequently asked

How often can it be repeated? A full course usually every 1–2 years; short top-ups once a year.

Can it be done while breastfeeding? Because data are limited, postponing until after breastfeeding is advised.

Can teeth be whitened straight after orthodontics? 2–4 weeks after the brackets come off, once enamel and gums have recovered.

Solutions by cause: Why do teeth turn yellow? · Treatment: Teeth whitening