Teeth Whitening/ Bleaching

Teeth whitening or bleaching allows discoloured, yellowed teeth to be restored to a more aesthetically pleasant lighter shade.

Bleaching can be carried out either at home, with a home delivery system or in the dentist's chair with an office bleaching system.

How does bleaching work?

Whitening of teeth is achieved by the application of a bleaching agent- either carbamide peroxide or hydrogen peroxide. Carbamide peroxide breaks down to give hydrogen peroxide. The hydrogen peroxide then breaks down into perhydroxyl and oxygen when activated. These penetrate the tooth enamel and react with the stain molecules, rendering them colourless. The breakdown of the peroxides can be accelerated with a bright light. As carbamide peroxide takes longer to break down, it is more stable and can be left on the teeth surfaces for longer periods. 

In Australia, ONLY registered dental practitioners are allowed to carry out teeth whitening procedures or supply bleaching gels where the gel concentration exceeds 6%. 

Home bleaching

Custom-made bleaching trays are supplied along with the bleaching gel kit. The bleaching gel is placed in the trays and these are worn for a minimum of 1 hour/day over a few weeks until the desired result is achieved. The ACCC prohibits the supply of home bleach that contains more than 6% hydrogen peroxide or more than 18% carbamide peroxide. Hence, the bleaching gels supplied will not exceed these concentrations. 


  • Allows a measure of control on the degree of whitening. The longer one uses the bleaching system, the whiter the shade obtained. 
  • The trays carry a one-off cost and if looked after, can be kept for years. Bleaching gel can be obtained as necessary.


  • Discipline in wearing the trays for the required length of time is needed if results are to be seen
  • Teeth can become transiently hypersensitive. It is advised that the bleaching process is discontinued for a day or two if the teeth become too sensitive. Bleaching can be resumed once sensitivity levels have reduced. 

Office bleaching

Bleaching is carried out in the dental surgery. Protective barriers are applied to protect the lips and gums. Four to five applications of hydrogen peroxide bleaching gel (maximum concentration 37.5%) are carried out. A bright light is applied to the gel after placement of the teeth surfaces. This activates the peroxide to achieve the whitening effect. The total time for the process can take up to 1.5 hours. It is absolutely necessary to ensure the teeth and gums are healthy before bleaching is carried out. If necessary, a scale and clean is carried out to ensure the teeth surfaces are free of plaque and calculus. 


  • Once-off process that delivers good results for those who are time-restricted for home bleaching or who need more immediate results


  • The degree of whitening cannot be predicted as this is a once-off procedure. Extremely discoloured teeth might need more than one session of office bleaching to achieve desired result or might need to be supplemented with home bleaching.
  • Slightly more heightened sensitivity of teeth to cold can be expected after the procedure. This is a transient effect that can last a day or two.

Is Bleaching safe?

  • Carbamide and hydrogen peroxide do not cause any morphological changes to the tooth enamel when the tooth is healthy and free of decay.
  • The increased sensitivity to thermal stimulus (hot or cold) is a transient effect and does not represent a danger to the tooth.
  • While there are no adverse effects to the teeth, exposure of soft tissues (gums, lips, oral cavity and digestive system) to the peroxide can lead to severe burns and irritation. This is why it is strongly advisable to ensure that dental bleaching procedures and supply of bleaching gels are carried out by a qualified and registered dental practitioner. 

If done correctly and with the correct supervision, dental bleaching is safe. 

When is bleaching not recommended?

  • In the presence of untreated dental decay, gum and mucosal disease, bleaching is not recommended. Bleaching is safest and most effective when teeth and soft tissues are healthy.
  • Bleaching is also contra indicated for pregnant and lactating women.
  • Teeth that have been restored with large fillings, crowns or veneers cannot be bleached adequately. While natural tooth enamel can be bleached, the materials used for fillings and the ceramic in crowns and veneers will not change colour. This can result in a discrepancy between the colour of the natural teeth and those that have been restored. It is advised that bleaching is carried out before the placement of crowns and veneers on teeth. If old fillings are present, they might need to be replaced after the bleaching process if a colour discrepancy arises between the bleached enamel and the colour of the filling material.