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hydrogen peroxide

How Does Tooth Whitening Work?

How Does Tooth Whitening Work?

Tooth Whitening: Implications and How It Works

Tooth whitening, also referred to as ‘vital bleaching’, is a non-invasive way of lightening discoloured teeth. This procedure is often requested by patients and is considered cosmetic; therefore most insurance companies do not cover the cost. There are three primary reasons for having tooth whitening:

  1. Extrinsic stains: food, cigarettes, coffee, tea
  2. Aged teeth
  3. Intrinsic stains: mild tetracycline or fluorosis

Your teeth are made up of different layers, the first being enamel. Enamel is porous, so when you drink coffee, tea, smoke, or eat anything that has color dyes it creates a stain. When whitening is used, the chemicals get into the enamel which creates an ‘oxidation reaction’- a chemical reaction in which oxygen reacts with another atom, molecule, or compound to produce a new substance, thus making it able to break down the stain.

Treatment Options with Tooth Whitening Products

In-office whitening usually takes up to 1 ½ to 2 hours to complete. This results in immediate changes in your teeth. This type of whitening is only available in-office because of the high concentration in 38% hydrogen peroxide gels. When arriving at the office, your health care provider will place a barrier above your teeth just at the gingival to protect your gums from the product.

At-home treatment consists of custom-fitted bleaching trays. This is a very thin plastic that you place the whitening gel in and, depending on the percentage of hydrogen peroxide, these trays will stay in place from 4-10 hours a day. These are usually worn to bed unless you have time during the day to wear them.

Over-the-counter whitening strips are thin, clear strips that contain no more that 6% hydrogen peroxide. They are placed on the facial part of your teeth, and the remaining portion wraps around the inside of your teeth, making sure you adapt the strip to all facial surfaces (especially along the gum line). These usually stay on for no more than 30 minutes, twice a day. Because of the lower concentration, it will typically take a week to see results.


The main purpose of tooth whitening is to achieve a whiter smile. This could be easily achievable by doing either in office, take home, or strips. By doing an in-office procedure you will see results instantly, and will continue for the next 24 hours. Take-home is an easy application by putting the gel into your trays and going to sleep or leaving them in to do stuff around the house, though this approach could take anywhere from 30 min to 8 hours depending on the strength of hydrogen peroxide. White strips are simple and quick. Apply strips for 30 minutes 2 times a day, but because of the little percentage it could take a week to see results.


There are two major adverse effects of tooth whitening. The first is thermal hypersensitivity, 'temperature-sensitive teeth'. Breathing through your mouth, or drinking hot or cold beverages can cause sensitivity. When this happens, the best way to prevent sensitivity is to use a tooth-paste high in fluoride. The other side effect is tissue irritation. Excess gel can seep out of the trays or when in office the barrier can leak causing the hydrogen peroxide to have contact with your gums creating a stinging sensation. To prevent this from happening, when loading your custom trays you should apply very little into the wells. If some does leak out, you can wipe excess gel as soon as you notice it. Also, for those of you who have crowns, veneers, or fillings in the front teeth: these do not whiten. If you are thinking about whitening and have this issue, you can always whiten until you are happy with your shade and then get those fillings re-done so your dentist can match that shade.

Which Product Do We Use?

At Longworth Dental, our main whitening product is Opalescence. In-office and take-home products can be purchased. For take-home products, you will be required to come in for impressions of your teeth to make your custom bleaching trays. Once this is completed, you will receive a starter kit that contains 8 carpules. This should last 8 treatments. Instructions on how to take care and load your trays are included. For full-mouth whitening, it costs $300: $150 for your upper arch and $150 for the lower. ‘Touch up’ kits are also available containing 4 carpules for $25

For a more affordable approach we offer Crest White Strip Supreme. These different than over the counter strips by having 80% more hydrogen peroxide, they come with a strip for lower and upper arch in one pouch. You can purchace a box of 42 pouches (84 strips in total) for about $38.