the Australian Dental Association
Written by the Australian Dental Association, Nov 20, 2021
Fact Checked

Teeth whitening is the process of lightening the colour of the teeth. This treatment is best performed by a dental professional, such as a dentist, dental hygienist or oral health therapist.

What is teeth whitening?

Teeth whitening aims to lighten the colour of the teeth. This treatment is performed in an attempt to whiten or lighten the shade of teeth that appear dark or discoloured. There are many reasons why teeth may be discoloured. Dental professionals are best placed to diagnose the reason for tooth discolouration and provide advice on whether tooth whitening will be an effective treatment.

Hear more about tooth whitening from Associate Professor Laurie Walsh on the Watch Your Mouth podcast.

What causes tooth staining?

Over time, your teeth can go from white to not-so-bright for a number of reasons. Common reasons include foods and drinks, tobacco, age, medications and trauma. Food and drinks such as coffee, tea and red wine are some major causes of staining. The intense colour pigments of these drinks are called chromogens. The chromogens attach to the white tooth enamel causing it to appear darker.

The chemicals tar and nicotine in tobacco are well known causes of tooth discolouration, turning the teeth a yellowish colour. As people age, the enamel layer can become thinner allowing the inside dentine to show through. Dentine is yellowish in colour and therefore makes the tooth appear darker when the enamel thins.

A traumatic injury to the teeth can cause the affected tooth or teeth to become darker over time. The injury can cause the tooth to create more dentine to protect the dental pulp but this can make the tooth visually appear darker. Trauma can also cause blood from inside the tooth to leak into the surrounding tooth structure leading it to appear discoloured.

Some medications are known to cause tooth staining as a side effect. Young children who are exposed to antibiotics like tetracycline and doxycycline when their teeth are forming (either in the womb or as a baby) may have discoloration of their adult teeth later in life.

Extrinsic staining

Stains that are on the outside surface of the tooth are known as extrinsic stains. Examples of causes of these stains can include tea, coffee, red wine and smoking. Depending on the type of staining, it may be able to be removed while brushing with whitening toothpaste as well as professional dental cleaning or by chemical treatment.

Intrinsic staining

Staining that is located inside the tooth's structure is known as intrinsic staining. Potential causes can include medications taken during tooth development, trauma causing blood from inside the tooth to leak into the surrounding tooth structure, amalgam (metal) fillings or root canal treatments.

Removing stains that are based inside the tooth can be very difficult if trying to treat from the outside surface. Depending on the cause of the tooth discolouration, treating the tooth from the inside may be possible.

Teeth that have been injured and undergone root canal treatment may appear discoloured. This is an example of when tooth whitening treatment can be used on the inside of the tooth. The whitening treatment is placed in the centre of the tooth where the dental nerve was once located. It is left inside the tooth for several days before being cleaned out and the tooth fixed with a filling. This treatment is called internal bleaching and can only be done by a dental professional. The internal bleaching treatment may be followed by a crown or veneer treatment.

Whitening ingredients

Teeth whitening completed by dental professionals involves chemically treating the teeth with hydrogen peroxide or carbamide peroxide. These are the main ingredients used in tooth whitening products by dental professionals in Australia. The strength of the tooth whitening gel used depends on whether the treatment is completed at a dental clinic or at home. Higher strength gels can be used by dental professionals.

Hydrogen peroxide is also included in some 'whitening toothpastes' at levels of 1 to 3%.

Phthalimidoperoxycaproic acid, more easily referred to as PAP, is another ingredient that can be found in toothpastes aimed at whitening teeth. This is organic peroxide that acts like a bleaching agent.

Treatment options

There are two main ways a dental professional can provide treatment to whiten teeth - 'in-chair' or 'take-home' whitening.

In-chair tooth whitening

In-chair or in-office tooth whitening treatment is performed by a dental professional whilst you are sitting in the dental chair. This treatment uses concentrated solutions of hydrogen peroxide. You should leave your dental appointment with whiter teeth. Your dentist may also suggest continuing using take-home whitening treatment to maintain the whiter tooth colour at home.

A patient undergoing in-chair teeth whitening treatment at a dental clinic. Getty Images.

Take-home tooth whitening

Take-home tooth whitening treatment is completed at home by the patient under the supervision of their dentist. The dentist will custom-make thin, plastic trays that fit over the surface of your teeth only. At home, the tooth whitening gel is placed in these trays and then worn for a set amount of time. Your dentist will advise you on how to place the whitening gel in the trays, how much to use each time and how long to wear the trays for each time also. This method of tooth whitening does take longer than treatment completed in the dental clinic, but this does not mean that the final result is better or worse. Your dentist will discuss your options and provide advice on what type of treatment is best for you.

A custom-made teeth whitening tray and tube of whitening gel used for take-home teeth whitening treatment. Getty Images.

Tooth whitening toothpaste

Whitening toothpastes work by helping to reduce stains present on the outside surface of the tooth enamel. The toothpastes often contain special abrasives and/or whitening agents. Some toothpastes include the ingredient sodium hexametaphosphate, which can to repel stains from the surface of teeth. Hydrogen peroxide a common ingredient in teeth whitening gels are also added to toothpastes that aim to lighten the colour of teeth, at levels from 1 to 3%. Phthalimidoperoxycaproic acid, more easily referred to as PAP, is another ingredient that can be found in toothpastes aimed at whitening teeth. It is organic peroxide that acts like a bleaching agent.

What are the risks of teeth whitening products?

Care needs to be taken when using concentrated hydrogen peroxide whitening treatment. It can be harmful to the soft tissues in the mouth, such as the lips, gums and tongue. They must be protected from the whitening gel that is placed on the teeth. Sometimes, the nerve can also become irritated. If the whitening treatment goes on the surface of the soft tissues, it can cause chemical burns, which will often turn into ulcers before healing completely.

Tooth whitening can also cause the teeth to become more sensitive such as to cold temperatures. If tooth whitening gels are used incorrectly, the sensitivity can be very severe where even breathing in air can cause the teeth to be painful. Your dentist can provide you with advice before starting your teeth whitening treatment that can help to prevent or reduce tooth sensitivity.

Can I whiten my porcelain crowns, or veneers and white fillings?

Tooth whitening gel is made to lighten the colour of tooth enamel. The treatment will not change the colour of porcelain crowns or veneers or composite resin (white) filling materials. If you whiten your teeth and your fillings, crowns or veneers no longer match in colour, they may need to be replaced by your dentist.

If the teeth you would like to have whitened have been treated with fillings, crowns, or veneers, your dentist will discuss these with you prior to progressing with treatment.

DIY tooth whitening

Do-it-yourself (DIY) tooth whitening advice found online often suggests using baking soda mixed with water to create a paste to brush the teeth. Baking soda is a mild abrasive and it can help to manage light stains on the outside surface of teeth. Brushing the teeth with baking soda will not affect the colour inside the tooth. It is not recommended to do this as part of your daily brushing routine. Toothpastes with baking soda are preferred over at-home pastes. Ensure your toothpaste also includes fluoride to help protect your teeth from tooth decay.

DIY tooth whitening kits can be purchased online and in supermarkets and pharmacies but as mentioned above, there are risks associated with tooth whitening. Therefore it is best performed under the supervision of a dental professional.

If you are interested in teeth whitening, talk to your dentist to see whether the treatment is suitable for your teeth.

Read Why should I see a dentist for tooth whitening?


Teeth whitening is best performed under the care of a dental professional. They can help to diagnose the cause of the discoloured teeth and the best method to try and lighten the colour. Teeth whitening is not without risks and under their care, your dentist can help to minimise these.