Teeth whitening (also known as bleaching of teeth) should be differentiated from removal of extrinsic stains from teeth. Extrinsic stains includes teeth discoloration due to smoking; intake of staining food/beverages eg coffee and tea; medicines like chlorhexidine mouthrinse as well as poor oral hygiene leading to accumulation of plaque and calculus. These stains can be removed effectively through professional scaling and polishing by your dentist.
Intrinsic stains refer to the discoloration of the tooth structure and not simply the surface of the tooth. Intrinsic stains therefore cannot be removed by scaling or polishing alone. Intrinsic discolouration can be caused by any of the following reasons:
- Caries or tooth decay
- Congenital malformation in tooth development eg amelogenesis or dentinogenesis imperfect Excessive ingestion of fluoride containing substances during tooth development leading to fluorosis
- Drugs eg tetracyclines
- Dead or non-vital teeth as a consequence of tooth decay or trauma
- Aging and thinning of the outer layer of the teeth (enamel)
Once the cause of the discoloration has been identified, then the most appropriate method of treatment can then be chosen. It is therefore important to consult a dentist before starting on any tooth whitening programme.
Bleaching or tooth whitening is a means to reduce/remove intrinsic stains. This can be achieved through various means but the most effective is through the use of dental products available in a dental clinic. This is because most products freely available in the pharmacy are not of the right concentration and therefore ineffective. More importantly, over-the-counter products may not adequately protect the surrounding gums from the caustic nature of some of the stronger bleaching agents. Another point to note is that bleaching agents will not have any effect on colour of existing fillings and crowns.
The teeth whitening procedures that dentists perform on vital teeth can be divided into 2 main categories:
- Chairside or in-operatory bleaching
- Home bleaching
Chair-side bleaching involves the application of hydrogen peroxide of varying concentrations to the external surface of the teeth followed by its activation by either a heat or light source. The whole procedure takes place on the dentist chair. Each treatment appointment can take up to 1.5 hours and it may take 2-3 appointments to achieve the desired outcome. A discernable difference should be observed immediately after the appointment and the need for a second/third follow-up bleaching appointment depends on the patient’s expectations.
Slight relapse is a common occurrence about 6 to 12 months after the initial bleaching although it is not usual for the colour of the teeth to totally revert to the pre-treatment colour. The management of such relapses may involve the use of either a home-use touch-up kit or requiring retreatment. Another common complication of bleaching is post-operative sensitivity and this tends to be more often for chair-side bleaching compared to the home bleaching kit.
Home Bleaching involves the daily placement of carbamide peroxide gel into a custom-fitted tray over the upper and lower teeth. As the name suggests, it is carried out by the patient in the comfort of his own home and at his own convenience. Patients are usually advised to wear the gel-loaded custom tray for 3-4 hours a day (preferably overnight) for 2-3 weeks for the colour to stabilize. As the bleaching reaction is oxidative in nature, more frequent conscientious applications will result better and faster results. As the procedure requires less chair-side time, this method of teeth bleaching is a lot cheaper.
The other advantage of home bleaching is that this method is better able to achieve homogeneity in teeth colour if certain teeth need to be lightened more than others. There are also less complaints of post- operative sensitivity as home bleaching is a more gradual process. The alternative use of a fluoride gel can also greatly alleviate sensitivity during the bleaching process. Technically, home bleaching can achieve the same results as chair-side bleaching if patient compliance is good and time is not a critical factor.
There is no evidence that the clinical use of hydrogen and carbamide peroxide over the last 75 years to whiten teeth has lead to any harmful effects to the underlying teeth provided the chemicals are use appropriately. The surrounding gums should be adequately protected from the bleaching agent although minor ulceration or irritation may occur during the initial treatment. Therefore it is important to use these bleaching kits under the supervision of a dentist.