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Clinical / September 27, 2023

Brightening smiles with tooth whitening

by Anne Gormley


Anne Gormley discusses tooth whitening and explains how the treatment can rejuvenate smiles and boost confidence.

A bright, white smile can have numerous benefits, from helping to boost confidence, improve oral health and give a great first impression. However, over time, teeth can turn yellow. This can be down to one of a number of reasons, including ageing, poor dental care or consuming tooth-staining foods and drinks such as tea and coffee. 

Since being introduced more than 30 years ago, tooth whitening has become a popular treatment for patients, and dentists alike. In fact, tooth whitening treatment (especially in men) is one of the fastest growing treatments in cosmetic dentistry. 

Typically, the results are quick and treatment has a high degree of success, producing wonderful outcomes and satisfied patients.

Understanding yellow teeth

To understand tooth whitening, we first need to understand why teeth turn yellow. Enamel can wear away over time, revealing the yellowish dentine beneath. Also, habits like smoking or drinking dark beverages can leave stains on our teeth, making them look yellow. 

Several factors contribute to the discolouration of teeth. Awareness of these causes can help individuals make informed decisions about their oral care. 

Factors for discolouration

  • Ageing – enamel naturally thins as we age, revealing more of the yellowish dentine underneath. This age-related wear and tear can result in a gradual change in tooth colour
  • Dental trauma – injuries to the teeth can lead to the formation of dark stains caused by the breakdown of blood products within the tooth structure
  • Dietary habits – food and drink can play a significant role in tooth staining. Dark-coloured substances like coffee, tea, red wine and certain berries contain chromogens that attach to the enamel, leading to yellowing over time. Similarly, acidic foods can erode the enamel, making teeth more susceptible to staining
  • Genetics – some people are genetically predisposed to have thicker or thinner enamel, affecting the overall colour of their teeth. Genetics can also influence the susceptibility to staining or the rate of enamel erosion
  • Medications – certain medications, such as antihistamines, antipsychotics, and high blood pressure drugs, can cause tooth discolouration as a side effect. This is often a result of chemical interactions or changes in saliva composition
  • Medical conditions – certain medical conditions, like enamel hypoplasia (insufficient enamel formation), can lead to discoloured or yellowish teeth
  • Poor oral hygiene – inadequate dental care can lead to plaque build-up on the teeth. Over time, this plaque can harden into tartar, which not only contributes to tooth decay and gum disease but also attracts stains.

Whitening methods

While yellowing teeth can be distressing for patients, the good news is that brightness can be restored using one of several tooth whitening methods, such as professional tooth whitening treatment in the dental practice, at-home whitening or natural remedies.

Some patients may prefer natural methods – such as brushing with baking soda or using activated charcoal – for tooth whitening. 

While these remedies are generally safe for patients to try, they lack scientific evidence for their long-term effectiveness. 

The effectiveness of tooth whitening depends on several factors, including the severity of discolouration, the chosen method, and individual variations. 

Back to basics

Patients decide to undertake tooth whitening for a variety of reasons, including weddings, formals and graduations. Very often patients just want to lighten their teeth to improve their self-esteem and to make the teeth look brighter and fresher.

Generally, at-home whitening treatment takes three weeks, although if the patient doesn’t want to treat both arches every night then treatment can be extended to six weeks. 

The dentist will take either a scan or impressions to construct upper and lower customised trays ready for the patient to apply the bleaching agent while at home. 

Bleaching agents for whitening

There is a choice of three different bleaching agents, although they all contain the active ingredient hydrogen peroxide:

  • 10% carbamide peroxide
  • 16% carbamide peroxide 
  • 6% hydrogen peroxide. 

The gold standard treatment for tooth whitening is using customised bleaching trays and 10% carbamide peroxide. In some cases, 16% carbamide and 6% hydrogen peroxide are also used. Some patients prefer the 6% hydrogen peroxide syringe, as they only have to wear the trays for one to one and half hours per day.

There are also hybrid systems on the market, which combine all three bleaching agents. For instance, the protocol for Enlighten is as follows:

  • 14 days prior to treatment: Enlighten serum
  • Week one: 10% carbamide peroxide overnight
  • Week two: 16% carbamide peroxide overnight
  • Week three: 6% hydrogen peroxide for one hour per day
  • Post-treatment: Enlighten toothpaste.

Hydrogen peroxide versus carbamide peroxide

Hydrogen peroxide consists of hydrogen and oxygen. Carbamide peroxide is a chemical that is made up of hydrogen peroxide and urea. It breaks down slower that hydrogen peroxide, releasing 50% of its whitening effect during the first two hours of application and the rest over the next six hours. The concentration reduces by a half every two hours so the optimum time to wear the tray is four to four and a half hours.

Both carbamide and hydrogen peroxide are oxidising agents (ie, they are both reactive when they are exposed to oxygen). It’s this oxidising process that breaks down stains, leaving them brighter and whiter. 

Both can cause sensitivity, however there is typically no difference in the amount of sensitivity between carbamide peroxide and hydrogen peroxide. Neither carbamide nor hydrogen peroxide cause rebound, which means that they do not cause the teeth to look whiter straight after the treatment.

The difference between the two is that hydrogen peroxide breaks down much quicker and is released in 30 to 60 minutes. In addition, carbamide peroxide has a longer shelf-life than hydrogen peroxide. 

If the teeth are dark, or the patient wants very bright teeth, 16% carbamide peroxide is used. Although sensitivity may be a bigger issue with the higher concentration. The loaded tray is worn for four hours per night and the patient must not eat or drink while wearing the trays. 

The trays are accurately made to fit the patient’s mouth with special reservoirs to hold the bleach against the teeth and ridges to prevent the bleach impinging on the gums, which reduces any risk of gum inflammation. The concentration of the bleach given by the dentist is much higher than that obtained over the counter. 

Unpredictable results 

There are a few patients where tooth whitening is not advisable.

For instance, it may not be advisable to carry out tooth whitening on someone who has experienced tetracycline staining. Tetracycline staining can occur from taking tetracycline drugs. It is advisable to let patients who have experienced tetracycline staining know tooth whitening will either not work or will produce a banded appearance.

Fluoride mottling (fluorosis) can also produce unpredictable results so it’s important to explain to the patient that it may be necessary to carry out restorative work using composite materials to mask the mottled appearance. The area with fluoride mottling is likely to appear more fluorescent after tooth whitening than the unaffected portion of the teeth.

In addition, pregnant and breastfeeding women are not advised to undertake tooth whitening.

Results and aftercare advice

It’s crucial to manage patients’ expectations, as tooth whitening results can vary and not everyone’s teeth will become perfectly white.

Some patients might see great improvements after one professional treatment, while others might need a few sessions. The variation in results is normal and depends on factors like the original tooth colour, enamel thickness, and lifestyle habits. 

In addition, to help maintain the new bright smile, patients should practise good oral hygiene by brushing and flossing regularly. In addition, recommend reducing the consumption of staining substances like coffee, tea or tobacco. Advise the patient to schedule regular dental check-ups, which will also help monitor the patient’s oral health and keep their smile shining.


Tooth whitening is a fantastic option for rejuvenating smiles and boosting confidence. Finding the right method can help brighten yellowing or stained teeth. However, as results can vary and achieving the desired level of whiteness may take time. Especially for severe discolouration, managing patient expectation is vital. 

From the patient’s point of view, consistency and patience are key to seeing the best possible outcome.

With the right treatment and proper care, patients can achieve a radiant and healthy smile that leaves a lasting impression. 

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