Whitening is the one cosmetic treatment where the cheap option sometimes genuinely works and the expensive option sometimes genuinely does not.

What determines the outcome is not the price. It is what is actually causing the discolouration — and that is worth establishing before you spend anything.

Why teeth darken

This determines which treatment will work, so it comes first.

Surface staining from coffee, tea, red wine, tobacco and curry. Sits on the enamel. Responds well to whitening, and a good deal of it comes off with a professional clean alone.

Age-related darkening. Enamel thins over decades and the dentine beneath — which is yellower — shows through more. Responds reasonably well, though there is a limit.

Deep intrinsic staining — tetracycline banding from childhood antibiotics, fluorosis, or a single dark tooth after trauma or root canal treatment. Whitening may improve these modestly or not at all. Tetracycline staining in particular often needs veneers to address properly, and no amount of whitening will change that.

Restorations that no longer match. Not discolouration at all. An old crown that has darkened, or bonding that has stained, will not whiten, and whitening the teeth around it makes it more obvious rather than less.

A five-minute look tells us which of these you have. It is the difference between money well spent and money wasted.

The three options

Over-the-counter

Strips, pens, whitening toothpastes. Inexpensive.

Whitening toothpastes mostly work by abrasion — they remove surface stain rather than changing the colour of the tooth. That is a real effect, but a limited one, and the more abrasive ones wear enamel and scratch composite over time.

Strips contain genuine whitening agent at low concentration. They can lighten teeth somewhat. Their limitation is fit: they follow the arch loosely, so coverage is uneven, and gel contacting the gums causes irritation.

Worth trying for mild surface staining. Not worth persisting with if it is not working after a full course.

Professional take-home trays

Trays made from impressions of your own teeth, with a professional-strength gel used at home for a period each day over one to two weeks.

For most people this is the best value in whitening. The custom fit is the whole point — gel sits against the tooth surface evenly and stays off the gums. You control the pace, and if sensitivity builds you simply take a night off.

The trays last for years. Topping up later costs only the gel, which is a small fraction of the original price. That is the part people do not factor in when comparing options.

In-office whitening

A high-concentration gel applied in the practice with the gums protected, usually over an appointment of an hour or two.

The advantage is speed — a visible change the same day, which matters if there is an event next week. The cost is several times a take-home kit.

Worth being clear: in-office whitening is faster, not necessarily lighter at the finish. Take-home trays used properly over two weeks reach a comparable place. Many practices, ours included, combine them — in-office to start, trays to maintain.

Sensitivity tends to be more pronounced with in-office treatment, because the concentration is higher.

Sensitivity

Common, and the reason people abandon treatment halfway.

It is usually short, sharp sensitivity to cold during and shortly after treatment, and it resolves within a day or two of stopping. It does not indicate damage.

What helps: a sensitivity toothpaste for a week or two before starting, shorter sessions, taking days off rather than pushing through, and avoiding very hot or cold drinks for a day after each session.

If you already have sensitive teeth, say so before starting rather than after.

What will not whiten

Worth stating plainly, because it is the commonest disappointment.

Crowns. Veneers. Bonding. Fillings. None of them respond to whitening agents at all.

If you have visible restorations on your front teeth, whitening the natural teeth around them will make the mismatch worse. The usual sequence is: whiten first, let the shade settle for a week or two, then replace the restorations to match.

That is not a reason to avoid whitening. It is a reason to know the full plan and the full cost before starting.

How long it lasts

Typically one to three years, depending almost entirely on what you drink and whether you smoke.

A heavy coffee drinker will see it fade sooner. Topping up with your existing trays for a night or two every few months keeps it stable and costs very little.

Rinsing with water after coffee, tea or red wine helps more than most people expect.

On safety

Professionally supervised whitening at appropriate concentrations is well established. The concerns worth knowing about:

Gum irritation from poorly fitting trays or over-filled gel — which is exactly what custom trays prevent. Unregulated high-concentration products bought online, which can genuinely damage soft tissue. And whitening done over untreated decay or leaking fillings, which is why an examination comes first.

Whitening is also not recommended during pregnancy or breastfeeding, and it is not typically done for children.

Finding out what will work for you

The useful first step is a short examination to establish what is actually causing the colour — and, quite often, a professional clean, which resolves more staining than people expect before any whitening is needed. Book an appointment and we will tell you what a realistic result looks like for your teeth.

Common questions

Which option gives the best value?

Custom take-home trays, for most people. The trays last years and top-ups cost only the gel.

Is in-office whitening whiter?

It is faster. Take-home trays used properly reach a comparable result over a couple of weeks.

Will it work on my crowns?

No. Crowns, veneers, bonding and fillings do not whiten.

Does it damage enamel?

Professionally supervised whitening at appropriate concentrations does not. Abrasive whitening toothpastes used heavily over years can wear enamel.

How white will my teeth get?

Depends on the starting shade and the cause. Surface and age-related staining respond well; deep intrinsic staining often does not. We will give you a realistic expectation before you start.

What if my teeth become sensitive?

Take a day or two off, use a sensitivity toothpaste, and resume. It resolves after treatment finishes.

How long does it last?

One to three years typically, shorter if you smoke or drink a lot of coffee. Top-ups with your trays maintain it cheaply.

Should I whiten before getting veneers?

Yes. Whiten first, let the shade settle, then match the veneers to it. Doing it the other way round means replacing them.