The Romans used urine, we use lasers. What are the best methods to whiten your teeth?

People have long gone to great lengths for a pearly white smile. The ancient Romans used urine as a mouthwash to whiten their teeth, the ammonia proving handy for lifting stains. In Elizabethan England, people reportedly kept their smiles bright by rubbing their teeth with powdered fish bones, then rinsing their mouths out with vinegar and sulphuric acid.

Our methods have changed significantly over time (and thankfully no longer involve human waste), but we’re still just as intent on keeping our teeth white. Whitening trays, gels, lasers and charcoal toothpastes are all offered as solutions for teeth whitening.

But just how effective are they, and what causes our teeth to stain in the first place?

Why do teeth discolour?

Associate professor at the University of Melbourne and dental public health expert Matt Hopcraft says teeth staining or discolouration can be either surface (extrinsic) or internal (intrinsic).

“Extrinsic staining is most commonly caused by dietary factors like coffee, tea, red wine or tobacco smoking. Poor oral hygiene – lack of brushing and flossing – can then contribute if stains aren’t removed,” he says.

These surface stains are usually the easiest to remove. However, some teeth can discolour internally due to factors like age and trauma (damage to the nerve and blood vessels can result in discolouration).

Erosion of the outer layer of enamel can also cause teeth to go slightly yellow, Hopcraft says, since it exposes the yellowish underlying tooth structure, dentine. This is especially common among those with highly acidic diets and those who frequently drink soft drinks, sports and energy drinks and wine.

Sometimes, it’s just genetics, says Australian Dental Association aesthetic dentistry spokesperson Dr Fadi Yassmin.

“You can be born with a set of teeth that are slightly less white than the general population. There are also developmental factors – sometimes, taking a certain antibiotic, say, before the age of 11 or 12, can cause staining, or more heavily discoloured enamel.”

I love coffee. What else can I do?

The best way to minimise tooth discolouration, regardless of what you eat and drink, is to carefully clean your teeth regularly. This includes a professional dental clean every four to six months.

Emeritus Professor Laurence Walsh, from the school of dentistry at The University of Queensland, says this is because cleaning your teeth removes the “glue” that most materials stick to.

“Plaque grows on the surface of teeth, and the material that sticks the plaque to the teeth is called dental pellicle. If you have teeth that are fundamentally covered with invisible layers of plaque, then there’s more glue that things can stick onto,” he says. “But if your teeth are smooth and well-polished, there’s less surface area for stuff to stick on.”

However, if you’re intent on a whiter smile, Walsh says there are both in-clinic and at-home options, with in-clinic methods being most effective.

“Clinic [treatments] will always deliver the best result because the technology used, which ranges from a particle jet device, also called an airflow, through to an ultrasonic scale, can get rid of every type of external stain completely,” Walsh says.

At-home treatments are still popular, however, including whitening gels, LED mouth trays, strips and whitening toothpastes. Hopcraft says you can generally expect teeth to go anywhere from three to eight shades brighter with professional applications, but only about one to two shades lighter with take-home kits.

Since dental procedures (especially cosmetic ones) aren’t covered by Medicare, most people will have to pay for whitening treatments upfront. Some private health insurance plans may cover dental procedures via their extras coverage; however, this varies depending on the insurance provider.

According to price comparison website Canstar, professional teeth whitening can cost anywhere from $500 to $2000 per session. At-home kits, on other hand, usually cost between $300 and $600, or even as low as $30 if you’re buying over-the-counter products.

Regardless of which method you use, Yassmin says you must consult a dental professional first.

“There are certain cases where there’s a good chance the patient won’t even notice the result because of worn enamel, or there could be old fillings or bonding that they didn’t realise they had – you can’t whiten those,” Yassmin says. “Once you have the assessment, the dentist can manage your expectations and desired outcomes.”

Do whitening toothpastes work?

Whitening toothpastes are better used as maintenance for those who have already had their teeth professionally whitened, Yassmin says. However, many of these products – including charcoal toothpastes and “smokers’ toothpastes” – contain harsh abrasives like silica, which can wear away enamel.

“That’s the last thing you want,” Yassmin says. “Once the enamel is gone, you’re not going to be able to whiten the next layer because whitening only works on the enamel. Anyone with a lot of dentine exposure is just going to be irritating that layer and won’t get any sort of aesthetic effect.”

When looking for a whitening toothpaste, Yassmin says those containing peroxide are fine since only a certain dose can be reached in an at-home paste. Those containing silica or other abrasives, however, should be avoided.

Whitening toothpastes can only go so far, though, Walsh notes. Though they can be quite effective for removing external stains, toothpastes will do little to remedy internal discolouration since they’re merely a topical product.

Is teeth whitening worth it?

It’s not uncommon to experience some discomfort while receiving a hydrogen peroxide treatment. This is because the solution can cause “zingers” and burns on the gums, Walsh says. Those already predisposed to tooth or gum sensitivity could find this method rather painful.

A peroxide-free solution has been developed (PAP), however, which has proven more comfortable for many people.

Regardless, Walsh advises pregnant and breastfeeding people avoid any whitening other than toothpastes.

“The biggest thing to be on the lookout for are the bleaching products sold on social media that fall outside the legal scheme in Australia,” Walsh says. “People try to sneak [high-strength products] in through online sellers like eBay … Keep your eye out for things that make ridiculous promises, like that the product can bleach fillings.”

And though teeth whitening is generally safe, there are limits to how white a smile can get.

“There are saturation points,” Yassmin says. “Teeth that are medium-to-light often go a lot whiter because they’re able to more easily absorb the whitening material. It’s usually the darker teeth that will only maybe change two or three shades, whereas others can go five or six shades lighter.”

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