Does Purple Toothpaste Whiten Teeth?

Purple sits opposite yellow on the colour wheel, so the two cancel each other. A purple toothpaste, serum or strip leaves a very thin layer of violet pigment on the surface of the enamel. Under light, the yellow tint of the tooth is neutralised and the tooth looks whiter, in the same way a violet rinse is used on grey or yellowed hair.

No chemical change happens in the tooth. There is no peroxide in the mechanism, and the pigment never enters the enamel. What you see is an optical effect, and it exists only while the film is there.

The film is thin, so eating, drinking, brushing and saliva wear it away. Depending on the product, the brighter look can last from a few hours to a day or so before you reapply. When it has gone, your teeth are the same colour they were before.

That is not dishonest if you know what you are buying, and a purple product can be useful before a photograph or an event. The same idea is used by blue pigments in some whitening pastes, covered in the page about whether whitening toothpastes work. It becomes a problem only if you expect it to replace whitening.

Searches for purple whitening strips often mean products that combine a violet colour with, or instead of, a bleaching agent. Read the ingredient list. If it names hydrogen peroxide, carbamide peroxide or a peroxide alternative such as PAP (phthalimidoperoxycaproic acid), some real whitening may happen on top of the colour effect. If it names only a violet pigment, the result is cosmetic.

Peroxide strips and what they can do are covered in the page on teeth whitening strips. If a product makes dramatic claims and lists no active ingredient, treat it with caution.

If you accept it as a cosmetic touch-up, a purple product is low risk and cheap, and some people like the quick lift before an event. Expect a subtle effect. Teeth that are only mildly yellow show the biggest change, and heavily stained teeth show little.

It also pairs with proper whitening. After a peroxide course, a purple product can take the edge off the yellow that returns as the teeth pick up stain again, though it does not replace a top-up of the treatment itself.

The effect looks different in different light. A shade that appears whiter in a bathroom mirror can look flat or slightly grey in daylight, so judge it outdoors before you rely on it.

Read the label for two things: whether it contains a peroxide or PAP, and what the abrasive is. A purple paste that is also strongly abrasive can wear enamel over time, which makes teeth look more yellow, the opposite of the goal. Choose a fluoride toothpaste with moderate abrasivity and treat the purple as an optional extra.

Use it on teeth that are clean. The pigment sticks best to a clean surface, and on teeth with a layer of plaque or tartar the effect is patchy. If your teeth look dull, a scaling first gives the violet film something clean to work on.

Violet only cancels yellow. It does little for grey or brown teeth, where there is no yellow to cancel, and it cannot lift deep staining from tetracycline or from fluorosis, a developmental change in enamel from too much fluoride during childhood (see dental fluorosis).

It also cannot change crowns, veneers or fillings, and it does nothing for a single dark tooth, which usually means the nerve has died and needs a dentist. Used on a tooth that is heavily stained, a violet film can leave a faint grey or lilac cast instead of a clean white.

If you want the tooth itself to be lighter for months rather than hours, you need peroxide, used with the gums protected and the teeth checked first. Options range from strips to dentist-made trays to in-chair treatment, set out in the page on the professional whitening procedure.

A scaling and polish comes first if stain from tea, coffee or paan is the cause, because surface stain does not need bleaching. Call the clinic to ask which whitening options are available, and see the smile design service for the wider picture.