Health Topics

Healthy Living

June 2011
Teeth Bleaching and Whitening
Dr. Karthik Venkataraghavan

Just about everyone wishes they had whiter teeth. Fortunately, there is an easy, painless way to make your teeth whiter with bleaching – a dental technique that can give you a dazzling, bright smile!

Although teeth seem very hard, their enamel has microscopic pores that discolour over time as we age, from smoking, and from staining substances that we eat and drink. In some cases, enamel discolouration occurs during early tooth formation from antibiotic and fluoride consumption. Bleaching simply removes stains from the enamel of your teeth.

Almost anyone can benefit from teeth whitening, and bleaching is ideal for people who have healthy teeth and would like to have a brighter, more attractive smile.

The teeth whitening process really works, and there are experts in all facets of cosmetic dentistry who can determine which technique will best suit your individual whitening needs. Although your teeth will not go back to their "pre-bleaching shade," depending upon your habits you may get some staining over time after the procedure is done.

We often recommend that you have a bleaching appliance made after six months so that you can touch up your bleaching, or brighten your smile before a special event. If you are soon-to-become a bride or groom, bleaching your teeth will ensure that your wedding photographs show off your perfect smile!

The Tooth Truth
The layer of the tooth that you can see directly in the mouth is the enamel layer, which is the only portion of the tooth that should lie above the gums. The natural colour of enamel is white, but it is translucent and the colour of the other structures that underlie it tend to show through. The material immediately under the enamel is called dentin. Its normal colour is yellow, but its structure is porous, and materials can permeate it, causing it to darken to a brownish yellow as we get older.

So, the colour we see when we look at a tooth in the mouth, is a composite of the colour of the enamel (which may permanently stain as we get older) and the underlying dentin (which darkens over the years due to its close association with the underlying nerve). This is the reason why simply brushing the teeth will not prevent the teeth from becoming darker yellow as we get older. You can brush all day, but you will not be able to brush away the natural internal colour scheme.

Bleaching Process
Root canal treated teeth tend to be dark because the dead nerve (which prompted the root canal treatment) turns a chocolate brown and permeates the surrounding dentin before the dead material is removed during the root canal procedure. This can be cleared using a bleaching solution. This is still the basic procedure used in some clinics today.
Later, it was discovered that even dark vital teeth (teeth with live nerves) could be bleached by soaking the tooth in the dental bleaching solution. This stuff is 10 times more concentrated than the type you can buy in the drugstore, and in order to use it safely, the dentist has to isolate the dark tooth with a rubber dam.The solution could penetrate through the enamel into the dentin and bleach out the dark colour.
Finally, it was found that a 10-percent carbamide peroxide solution could be applied to the teeth safely without fear of burning or otherwise damaging the mouth. This dilute solution, if kept in contact with the teeth long enough, bleached the teeth to a brighter colour.

Forms of Dental Bleaching

Whitening Toothpastes:
These are over-the-counter preparations that have a low concentration of carbamide peroxide. These toothpastes will work to brighten your teeth if you are a very good brusher, brush many times a day, and have a lot of patience.They are very useful, however in maintaining the whitening achieved by using trays and strips.

High Concentration Bleach in Custom Made Trays:
This is the type of system that you can get at a dental clinic. The bleaching material can only be bought with a prescription and must be applied using the custom trays that the dentist makes for you. Because of the high concentration of the agent, and the close proximity with the teeth made possible by the trays, this system produces very good results with regular use. The agents have been improved and strengthened over the years, and now the process is fairly easy.

In-office Bleaching:Some clinics offer a quick start bleaching procedure in which a concentrated bleaching gel is placed on the teeth and allowed to remain in place while being "activated" with a light source. Treatments like this tend to be faster, but they require additional chair time, though giving excellent results.

What Bleaching Cannot Do
  • Bleaching will not bleach out the black, brown or white colour imparted to teeth due to decay.Teeth should be repaired before bleaching is performed.
  • Bleaching will not bleach out darkness imparted to teeth by old amalgam fillings. Removing the old metal filling and replacing it with a new composite will usually accomplish this, but if the tarnish has penetrated deeply into the tooth structure, the tooth may remain permanently discoloured.
  • Bleaching will not generally improve the appearance of fluorosis if the patient grew up in a part of the country that had a high concentration of fluoride in the drinking water.
  • Bleaching is ineffective in reducing the irregular gray horizontal lines seen on patients with tetracycline stain in their tooth structure. Tetracycline stain is seen primarily in older patients who received tetracycline to treat ear infections when they were infants and toddlers.

Please Note
It's important to know that not everyone's teeth will "whiten" the same. It depends on the number of teeth involved and the severity of discolouration. Over-the-counter whiteners are not recommended, because they may cause problems associated with over-exposing gum tissues to the active whitening agent. Any bleaching treatment should be done under the dentist's supervision.

Dr.Karthik Venkataraghavan is Consultant Pediatric Dentist at Apollo Hospitals, Bengaluru.
  • The information on this site does not constitute medical advice and is not intended to be a substitute for medical care provided by a physician.
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