Want whiter teeth in just 10 minutes, without any pain or sensitivity?
That's the hard sell from HiSmile, an at-home teeth-whitening product that once boasted of a $10 million advertising budget for social media marketing alone, with celebrities and influencers including Kylie Jenner, Kim Kardashian and mixed martial artist Conor McGregor spreading the good word to their millions of followers.
But does HiSmile really work and, more importantly, is it safe?
CHOICE tip: If you're concerned about surface stains on your teeth, visit the dentist for a clean. If you have private health insurance with extras cover, you may not have to pay a gap.
Each HiSmile teeth whitening kit comes with enough gel for six applications, an LED light, a mouth tray, a shade guide and an instruction manual.
You attach the LED light to the mouth tray, apply the gel to the tray, put it in your mouth and switch on the light. The light switches off automatically after 10 minutes, whereupon you take out the tray, spit, and rinse your mouth out.
The ingredients in the gel include:
- Phthalimidoperoxycaproic Acid (PAP)
- Potassium Nitrate
- Sodium Bicarbonate
- Sorbitol, Water, Propylene Glycol, Glycerin, PEG-8, Cellulose Gum, Hydroxyethylcellulose, Xanthan Gum, Flavour, Sodium Saccharin, Methylparaben, Aloe Barbadensis (Aloe Vera) Leaf Extract, Chamomilla Recutita Flower (Chamomile) Extract, Punica Granatum Seed (Pomegranate) Extract, Propylparaben
HiSmile's new formula
The ingredients listed above are a new formula which HiSmile released in 2019.
The original HiSmile formula contained citric acid, sodium chlorite and sodium bicarbonate as the active ingredients. Citric acid can erode tooth surfaces and cause sensitivity, while sodium chlorite can be toxic in high amounts. Sodium bicarbonate was included for its 'mildly abrasive action' – it's included in toothpastes for this purpose, but if it's just sitting on your teeth it won't have this effect.
HiSmile's teeth whitening kit. Image: HiSmile.
Whether HiSmile works or not will largely depend on why your teeth are stained, says Professor Laurence Walsh AO, spokesperson for the Australian Dental Association.
"If the stains on your teeth are difficult or ingrained, it's unlikely to work," he says.
"But if your issue is with surface stains, such as those from coffee, tea, red wine, berries or sauces, products like HiSmile may reduce their colour, leaving you with less staining on your teeth."
Whether HiSmile works or not will largely depend on why your teeth are stained
HiSmile commissioned a test on 24 people aged 19–55, and reports teeth were on average 3.5 shades whiter after a single 10-minute session.
HiSmile also reported on the results of a test conducted on human tooth enamel samples, although didn't provide us with details about the test. This test found that the results after a single session were similar to the test on the 24 people, and after six sessions reported an improvement of over seven shades whiter.
However, explains Professor Walsh, the significance of this depends on several factors.
"How the shade change was measured and from what baseline shade influences the interpretation," he says. "Some shades such as mid-range yellows are easier to lighten than others (such as browns and greys for instance).
"A change of 3.5 shades is not especially impressive, given that some toothpastes with improved polishing particles achieve 2 or more shades improvement or more just by removing some external stain or by repelling stains.
"Professional dental whitening products dispensed by a dentist or treatments provided in a dental office show gains of 6–8 shades typically or more."
HiSmile says its kit is "designed to whiten and brighten teeth without pain or sensitivity". The test on 24 people for whitening – which is limited by its small size and being short-term – reported no increased sensitivity after a single session, and some people with pre-existing sensitivity reported less sensitivity.
One of the ingredients, potassium nitrate, makes nerves in the dental pulp less likely to fire off and is found in toothpastes for sensitive teeth. It generally needs to be used regularly over a period of time – twice daily for two weeks or more – to have an effect.
Another key ingredient in HiSmile is hydroxyapatite – also known as calcium phosphate – which is the main component of tooth enamel. While not widely available, it's found in some toothpastes to help strengthen teeth.
A change of 3.5 shades is not especially impressive, given that some toothpastes with improved polishing particles achieve 2 or more
HiSmile commissioned a study on human tooth enamel samples which found that the hardness of tooth enamel increased after six consecutive sessions, while a hydrogen peroxide treatment weakened tooth enamel.
Professor Walsh says, "There is no independent evidence that the form of hydroxyapatite used in HiSmile or the formulation of their particular gel will allow remineralisation to occur, or promote it.
"Hydroxyapatite is highly insoluble and chemically very stable, so simply adding some into a product does not necessarily mean there will be any benefit to teeth," he says.
"Remineralisation needs the correct chemical balance of calcium ions, phosphate ions and fluoride ions – in a bio-available form. Hydroxyapatite is the least bioavailable form because of its low solubility."
Because the mouth tray is one-size-fits-all and not specially fitted, you may need to use a lot more gel to coat your teeth. That's problematic because it could hurt your teeth and gums, and you could end up swallowing more of the gel.
Consumers who buy HiSmile but are disappointed in the results could be tempted to use more of it or keep the tray in for longer to get the results they're after. Without a professional monitoring progress and tooth condition, they may end up damaging their teeth.
HiSmile encourages regular use of its products – it says the results will last three to four weeks, and recommends you do a single treatment every two weeks. You can sign up to a gel refill subscription service, saving money and ensuring a regular supply of whitening gel.
HiSmile's range of toothpastes and tooth-whitening pen. Image: HiSmile.
Teeth whitening pen
HiSmile also sells a tooth-whitening pen with the same formula as the gel for regular one-minute touch-ups.
"The one-minute application time is effective at clearing up light everyday stains and will help maintain a brighter smile for longer," says HiSmile spokesperson, Koban Jones. However, he points out, it's no replacement for the kit.
HiSmile sells a set of Day & Night Toothpaste, and Pink Toothpaste for sensitive teeth.
None contain fluoride.
Jones says: "Our community has always been vocal about preferring a fluoride-free toothpaste, but due to the massive benefits fluoride provides your teeth, we needed to find an effective substitution.
Fluoride is the major active ingredient for dental caries prevention ... omitting that means that very little benefit will be achievedProf. Laurence Walsh AO, Australian Dental Assoc.
"We found a specific combination of key ingredients (Xylitol, L'arginine, Potassium Nitrate, Sodium Hexametaphosphate and Hydroxyapatite) would serve as an effective substitute. These ingredients have the ability to inhibit the growth of harmful oral bacteria, prevent the growth of plaque and tartar, and reduce dentinal hypersensitivity.
"Specifically, Xylitol has been proven by numerous studies to affect the ability of certain strains to adhere to the tooth surface, decreasing caries and reducing plaque formation."
However, Professor Walsh points out, "Fluoride is the major active ingredient for dental caries prevention using toothpastes, and omitting that means that very little benefit will be achieved.
"Many dental products include xylitol. The research on xylitol shows that a large and frequent intake in the diet is needed to have any benefit. Recent large scale clinical research does not show any meaningful impact on dental caries risk in real world applications."
The Night toothpaste contains activated charcoal which HiSmile says is an "effective and progressive whitening agent that removes surface stains from teeth".
The ADA warns against charcoal toothpastes, because they may be overly abrasive. There are also concerns that charcoal and bentonite clay (which is also found in the night toothpaste) are carcinogenic.
How do the costs compare to other treatments?
The HiSmile Teeth Whitening Kit, containing three tubes of gel (which the company says is enough for six uses), an LED light, a mouth tray and a shade guide, costs $99.99. A set of three gel refills costs $34.99, which will last 12 weeks if used as directed. Buying the gels on a subscription is a little cheaper, at $29.74 for three refills. HiSmile's tooth-whitening pen is also available for ($39.99)
Other whitening kits that make very similar claims about their effectiveness and contain gel, a mouth tray and light are available at the supermarket or pharmacy for less than half the price of HiSmile.
HiSmile also markets a range of other products, such as Day & Night toothpastes ($16.99 for two tubes) and Pink Toothpaste for sensitive teeth ($14.99).
Other toothpastes with micro-polishing particles, which can help reduce superficial stains, cost around $5.
Going to a dentist for teeth whitening will cost from around $300 to $1000, depending on the technology used and level of treatment required.
It's relatively early days for the new HiSmile formula, and there's a lack of long-term, independent testing for safety and effectiveness on large numbers of people.
While the small tests commissioned by HiSmile show some promise, the bulk of evidence for it comes from celebrity endorsements and positive customer reviews on the HiSmile website.
As Professor Walsh says, "The key issue I feel is that the onus of proof on the belief that PAP is safe and is also effective, rests with the manufacturers who choose it – after all there is high level evidence from systematic reviews and meta-analyses of randomised controlled clinical trials to support professional level home bleaching gels with carbamide peroxide and hydrogen peroxide, so that is the level that should be aimed for.
"I believe most people would want to know if a new and unproven ingredient was safe and also effective. To answer that question needs proper studies with the right design (e.g. suitable controls as well as comparison products)."
HiSmile has told us that more testing is on the way, and we look forward to seeing the results.
Stock images: Getty, unless otherwise stated.