DR. MABEL CHAN: Can teeth whitening kits be trusted?

An Dental

Before After using Teeth Whitening kit

When you smile, the world smiles back at you.

This old adage isn’t just an airy-fairy saying - Studies[1] show that happy smiley faces have a strong motivational effect on others, and that those who come across as cheerful tend to enjoy more social interaction than their long-faced peers. At the workplace, presentable teeth are thought to be a requirement for prestigious roles in many professions.

So, if your discoloured smile has been costing you your confidence and relationships either in or out of work, you’re not alone.

For those looking to brighten their smile at their own time, a home teeth whitening kit is convenient, readily accessible, and can usually be affordably purchased either online or over the counter. And if you’re considering using one, you’ll want to do so without any regrets or complications.

Can OTC teeth whitening kits be trusted? Here’s why we don’t think so.

How does teeth whitening work?

The human tooth contains substantial amounts of hydroxyapatite. The inner part of a tooth (dentine) contains about 70% hydroxyapatite, while the outer part of a tooth (enamel) is about 97% hydroxyapatite.

The original colour of pure hydroxyapatite is a colourless white. Consequently, natural enamel has a white colour with some translucency. However, due to long-term chemical and mechanical wear, the enamel in our teeth eventually becomes thinner and more translucent, exposing more of the yellowish dentine layer, which can in turn make teeth look stained or discoloured.

What kind of stains do you have? Tooth discolouration can be categorised into 2 main groups:

Intrinsic staining

This is attributed to factors such as genetics, age, use of antibiotics, high levels of fluoride, developmental disorders, and more. It can start before the tooth has erupted.

Extrinsic staining

This is largely due to environmental factors like smoking, pigments in food and drink, antibiotics, and metals such as iron or copper. Coloured compounds from such sources are adsorbed into dental pellicles or tooth surfaces, causing stains to appear.

What types of teeth whitening products are available today?

Apart from in-office teeth whitening, there is a broad range of over-the-counter teeth whitening products available that can help lighten teeth by 1 to 2 shades.

Such products are often marketed to target varying teeth discolouration problems. For example, did you know that there are toothpastes marketed specifically for smokers? These products claim to contain larger quantities of abrasives and detergents that reduce stains.

Here’s the lowdown on common teeth whitening products available in Singapore:

Whitening toothpaste
  • These contain more abrasives and detergents than standard toothpaste but do not contain bleach (sodium hypochlorite).
  • They may contain small amounts of carbamide peroxide or hydrogen peroxide, which are teeth lightening agents.
Whitening strips and gels
  • Whitening strips consist of a thin layer of peroxide gel on plastic strips. These are shaped to fit onto the buccal surfaces of the teeth.
  • There are a variety of white strip products on the market with varying instructions (eg. apply twice daily for 30 minutes for two weeks).
  • Effects are usually seen in a few days.
Whitening gels
  • These peroxide-based gels are “painted” directly onto teeth surfaces with a small brush.
  • These gels are usually applied twice daily for two weeks.
Whitening rinses
  • Such rinses contain oxygen sources such as hydrogen peroxide, which react with chromogens.
  • Rinses are usually used twice daily and can take up to 3 months to lighten teeth by 1 to 2 shades.
Tray-based teeth whitening
  • Available both professionally and over-the-counter, this method involves a fitted tray containing carbamide peroxide-whitening gel that is worn for 2 to 4 hours during the day or overnight.
  • Teeth are usually lightened by 1 to 2 shades in a few days.

Achieve White Teeth

Are home teeth whitening kits effective?

While the lure of OTC teeth whitening kits is understandable, what with their accessibility and price, research shows that not all products are effective. Studies have proven that whitening chewing gum, for example, is not any more effective than normal gum[2]. Dental clinics will be able to recommend and offer professional home whitening kits if you are keen.

Moreover, the clinical efficacy of whitening toothpaste remains hotly debated[3] – although whitening toothpaste can prevent superficial extrinsic tooth stains, the whitening effect seems to be insignificant and short-lived. Whitening toothpaste, like conventional toothpaste, cannot prevent teeth discolouration.

Can teeth whitening damage teeth?

The Health Sciences Authority in Singapore strongly warns that home teeth whitening products should not contain more than 0.1% hydrogen peroxide, and that if they do, they can only be supplied by registered dentists.

This is for good reason as well, as improper use of teeth whitening kits can lead to detrimental results such as:

  • Tooth sensitivity and gingival irritation[4]
  • Tooth surface roughening
  • Tooth enamel softening
  • Increased susceptibility of demineralisation
  • Degradation of dental restorations
  • Unwanted colour change of dental restorations

The benefits of in-office teeth whitening

The potential risks of home teeth whitening kits makes seeing a trained professional the better choice. Additionally:

  • A dentist will whiten your teeth without making them look fake: Unlike a trained professional, home whitening kits cannot cater to your skin tone, natural teeth colour, and overall appearance.
  • Your teeth whitening process will be more effective: In-office products have higher concentrations of lightening chemicals like hydrogen peroxide.
  • Your teeth will be better protected: A dentist will perform procedures to protect your lips and gums before applying any teeth whitening agents.
  • Your dentist has the right tools for teeth whitening: This includes laser or LED systems that increase the rate of the chemical reactions.
  • Your teeth whitening process will be faster: In-office tooth lightening treatments can deliver instant results in just one session.

Should I use a home teeth whitening kit or see a dentist?

If a teeth whitening kit is used as per the manufacturer’s instructions, it can prove safe and effective. But the potential risks remain and are best avoided with the help of an expert.

Furthermore, dental procedures should be tailored to the individual and is based upon factors such as:

  • The reason for or cause of the teeth staining
  • The type and extent of teeth staining
  • An individual’s dietary and lifestyle habits
  • The existence of previous dental restorations
  • The existence of any intraoral conditions

Fact remains that most patients are not often aware of the risks associated with teeth whitening kits, and may thus be ill-equipped to identify or manage adverse side effects. A professional on the other hand will be able to give advice on and tailor teeth whitening strategies, reduce potential risks, and optimise regimen benefits.

Does this mean you should avoid over-the-counter products entirely? Not necessarily – but they should be used for mild cases of teeth discolouration at best under the guidance of a dentist.

Teeth whitening is not just a skin-deep fix

It is increasingly undeniable that a good dental appearance is a crucial aspect of successful modern life.

Whether your teeth discolouration is mild or severe, it’s never too late to get to the root of your dental problems and polish up your life.

Have questions? Feel free to drop me a message and I’m happy to help!


  1. Nikitin, J., & Freund, A. M. (2019). The Motivational Power of the Happy Face. Brain sciences, 9(1), 6.
  2. Demarco, F. F., Meireles, S. S., & Masotti, A. S. (2009). Over-the-counter whitening agents: a concise review. Brazilian oral research, 23 Suppl 1, 64–70.
  3. Epple, M., Meyer, F., & Enax, J. (2019). A Critical Review of Modern Concepts for Teeth Whitening. Dentistry journal, 7(3), 79.
  4. Li, Y., & Greenwall, L. (2013). Safety issues of tooth whitening using peroxide-based materials. British dental journal, 215(1), 29–34.
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