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Teeth whitening isn’t permanent. Published sources give anything from a few months to around three years, depending on the method and, above all, on what you eat, drink and smoke afterwards.
Key facts
- No method is permanent. Teeth pick up new stains, and the shade drifts back a little over time.
- Most figures you read online have no source. The few measured ones come from studies of whitening trays.
- The light doesn’t change how long it lasts. LED, laser or no light at all: studies find no difference.
- Our own sessions: we haven’t measured how long results from The Smile Bar last, so we don’t quote a figure.
How long each whitening method lasts
| Method | Published range | Who says it | Type of evidence |
|---|---|---|---|
| Whitening by a dentist, in the clinic | 6 months to 3 years | Dental clinics, health media | Claims, no study cited |
| Whitening through a dentist | Around 3 years | UK National Health Service | Public health guidance |
| LED whitening | A few months to 3 years | Brands and clinics | Claims, no study cited |
| Laser whitening | 6 months to 3 years | Dental clinics | Claims, no study cited |
| Custom trays from a dentist | Stable for 1 to 2.5 years | A 2023 review of 24 studies | Measured |
| Whitening strips | 1 to 6 months | Clinics, health media | Claims, no study cited |
| Whitening toothpaste | Upkeep only | American Dental Association | It removes surface stains, it doesn’t bleach |
| LED session in a whitening studio | Not measured | No follow-up study found | None |
How long does LED teeth whitening last?
Brands and clinics quote anything from a few months to three years, without citing studies. What research does show is that the light makes no difference to the result: two analyses of clinical trials (21 trials and 28 trials) found that light-activated whitening did no better than whitening without light.
So how long LED whitening lasts depends on the gel, your starting shade and your habits, not on the lamp.
How long does laser teeth whitening last?
Clinics quote 12 to 18 months, or 6 months to 3 years. No study shows that laser lasts longer than other methods. We don’t offer laser: our guide to laser teeth whitening in Bangkok compares it with LED.
How long do trays, strips and toothpaste last?
- Trays: the best-studied method. A 2023 review found the colour stays stable for 1 to 2.5 years.
- Strips: 1 to 6 months according to clinics and health media, with no study behind the figure. More in whitening strips in Bangkok.
- Toothpaste: it keeps surface stains away for as long as you use it. It doesn’t change the shade of the tooth.
Is teeth whitening permanent?
No. Two things happen over time:
- New stains. Coffee, tea, red wine and tobacco colour the surface again.
- A slow drift back. In a study that followed people for 30 months after tray whitening, teeth had darkened somewhat, even after a professional cleaning.
Before and after an LED session at The Smile Bar.
What makes whitening fade faster
| Factor | What we know | Evidence |
|---|---|---|
| Smoking | Tobacco stains teeth and makes stains worse | American Dental Association |
| Coffee, tea, red wine, dark sauces | Frequent pigmented food and drinks build up stains | American Dental Association |
| Coffee right after whitening | Reduced the result slightly in one clinical trial | One trial, 2020 |
| No professional cleaning | In one study, the shade stayed stable for a year when stains were removed by cleaning | One follow-up study |
| Heavy discolouration to start with | More likely to come back | 2023 review |
| Age, thin enamel | Often mentioned by clinics | No source given |
The first 72 hours after your session
At The Smile Bar we ask you to avoid strongly coloured or acidic food and drinks, and tobacco, for 72 hours.
- Avoid: coffee, tea, red wine, dark sodas, soy sauce, curry, tomato, citrus, chocolate.
- Fine: water, milk, chicken, white fish, rice, plain noodles, bananas.
- Shortcut: with the Nano Protection add-on (750 THB), we lift this rule.
It’s a precaution: research on the “white diet” is mixed. The full list is in what to eat after teeth whitening.
How to make teeth whitening last longer
| When | What to do |
|---|---|
| First 72 hours | Pale, low-acid food and drinks. No tobacco |
| Every day | Brush twice. Use the whitening toothpaste and mouthwash included in your package |
| After coffee, tea or red wine | Rinse with water |
| Once or twice a year | A professional cleaning at a dental clinic |
| When the shade has dropped | A single touch-up session |
Every package includes a whitening toothpaste and mouthwash to take home.
How often can you whiten your teeth again?
No dental association sets an interval. Clinics most often mention every 6 to 12 months.
A touch-up makes sense when:
- your teeth look clearly darker than after your last session;
- you have an event coming up: see how to whiten teeth fast;
- any sensitivity from last time has completely gone: see does teeth whitening hurt?
What to expect at The Smile Bar
| Package | Whitening | Visit | Price |
|---|---|---|---|
| Single Whitening | 1 × 20 minutes | About 30 minutes | 2,399 THB |
| Double Whitening | 2 × 20 minutes | About 60 minutes | 4,399 THB |
| Triple Whitening | 3 × 20 minutes | About 90 minutes | 5,799 THB |
- Result on the day: 2 to 9 shades lighter, 5 on average.
- How long it lasts: we haven’t measured it, so we won’t give you a number. It depends mostly on your habits.
- Not for: women who are pregnant or breastfeeding, people who wear braces, anyone under 18.
Book a session in Siam Square
- Where: ground floor, 392/27-28 Siam Square Soi 5, next to BTS Siam
- When: every day, 10 am to 8 pm
- How: book online, or walk in when a chair is free
Prices are on our teeth whitening prices page.
Frequently asked questions
Is teeth whitening permanent?
No. Teeth pick up new stains and the shade drifts back over time. How fast depends mostly on what you eat, drink and smoke.
How long does teeth whitening last?
Published sources range from a few months to around three years. The best-measured method, custom trays, stays stable for 1 to 2.5 years in studies.
How long does LED teeth whitening last?
Brands and clinics quote a few months to three years, without studies. Research shows the light doesn’t change the result, so it depends on the gel and your habits.
Does laser whitening last longer than LED?
No study shows that. Analyses of clinical trials found no type of light gives a better result than another.
Can I drink coffee after whitening?
We ask you to wait 72 hours. After that, rinsing with water after coffee helps your result last.
How often can I whiten my teeth again?
There’s no official interval. Clinics most often mention 6 to 12 months. Wait until any sensitivity has gone.
Does whitening toothpaste keep teeth white?
It helps with surface stains. It doesn’t change the shade of the tooth itself.
How long do you keep teeth whitening gel on for?
At The Smile Bar, each session is 20 minutes. More in teeth whitening gel explained.
