Whitening is the most requested cosmetic treatment we do and the one most often misunderstood. It is genuinely effective, it takes about an hour, and it is the least invasive thing in cosmetic dentistry — nothing is removed and nothing is added. But it only works on one thing: natural tooth structure.
How it works
A peroxide gel is applied to the enamel. It breaks down the pigment molecules trapped in the microscopic structure of the tooth. Nothing is stripped or sanded; the tooth is unchanged in shape and thickness, and the pigment inside it is simply broken up.
In-clinic whitening uses a stronger gel than anything sold over the counter, with your gums protected, which is why it does in an hour what home kits take weeks to approach.
What responds well
- Yellowing with age. Enamel thins over the years and the darker dentine beneath shows through. This responds reliably.
- Coffee, tea, red wine and tobacco staining. These are surface and near-surface stains, and they lift well.
- General dullness with no specific cause.
What responds poorly, or not at all
- Grey tones. Yellow lifts far better than grey. Greyish teeth, including those darkened by old tetracycline exposure, improve much less.
- A single dark tooth after a root canal. This is discoloured from the inside and needs internal whitening or a veneer or crown instead.
- White spots. Whitening lifts the whole tooth, so the spots usually remain visible — sometimes more so at first.
- Anything that is not tooth. This is the big one, below.
Crowns, veneers and fillings never change
Porcelain and composite do not respond to whitening gel at all. If you have a crown or a white filling on a front tooth and you whiten everything around it, that restoration stays exactly the shade it was — and will now stand out.
This is not a reason to avoid whitening. It is a reason to get the order right:
- Whiten first.
- Wait about two weeks for the shade to stabilise.
- Then have the crown, veneer or filling made to match the new shade.
Doing it the other way round means paying twice. If you are planning several treatments together, read planning a smile makeover.
Sensitivity
Some sensitivity for a day or two afterwards is common and normal — sharp, brief twinges to cold. It settles. A sensitive-teeth toothpaste in the week before and after helps a lot, and it is worth mentioning existing sensitivity beforehand so the gel and timing can be adjusted.
If you have untreated decay, gum disease or exposed roots, those get treated first. Whitening gel on an untreated cavity is genuinely unpleasant.
How long the result lasts
Realistically one to three years, depending almost entirely on what you drink and whether you smoke. Heavy coffee drinkers see it fade faster. Most people top up with home trays occasionally rather than repeating the full in-clinic treatment.
Nothing about whitening is permanent, and nothing about it is cumulative in a harmful way — repeated sensibly under supervision, it does not damage enamel.
If you are here for a few days
Whitening is a single appointment of roughly an hour, so it fits any trip, including the last afternoon. Two practical notes:
- For the first 48 hours, avoid coffee, tea, red wine, curry, soy sauce and tobacco. The enamel is temporarily more receptive to pigment, and Thai food is not a forgiving test of that.
- Whiten early in the trip if you are also having veneers or crowns made, so the technician can match the final shade.
How long does teeth whitening take?
In-clinic whitening is usually a single appointment of about an hour to ninety minutes.
Does whitening damage enamel?
Professionally supervised whitening at appropriate concentrations does not damage enamel. Sensitivity is common but temporary.
Will whitening work on my crowns and veneers?
No. Porcelain and composite do not change shade. Whiten first, then match new restorations to the result.
How long do the results last?
Typically one to three years, depending on coffee, tea, red wine and smoking. Home top-ups extend it.
Why is one of my teeth still dark after whitening?
A single dark tooth is often discoloured from the inside, usually after root canal treatment. That needs internal whitening or a veneer or crown rather than external gel.
Still not sure?
Tell us what is bothering you and we will tell you what it would take to fix — before you book anything.
