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Ambulatory Lightening: Teeth Whitening


1. How does a teeth whitening treatment work?

The carbamide peroxide included in the gel transforms into hydrogen peroxide (hydrogen peroxide H2O2) when in the mouth. The oxygen thus released passes through the enamel crystals and acts on the underlying dentin layer (yellow) in order to lighten the teeth.

2. How long does the dental whitening treatment take?

Unsually it takes two weeks, up to 6 weeks depending on the initial shade of your teeth. It is important to continue treatment until its end in order to obtain a stable result over time.

3. How long does a teeth whitening treatment last?

The color of your teeth will remain lighter for about 2 to 3 years, sometimes more, depending on the coloring agents present in your diet, your tobacco consumption and your dental hygiene, especially brushing your teeth (2 to 3 times a day).


See Question 7 for precautions to take during (and after) whitening to improve its results and duration, as well as a non-exhaustive list of coloring agents to avoid.

4. Can anyone have his/her teeth lightened?

Since tooth whitening using oxygen-based compounds, it can have negative effects when the patient's oral health is not good. It is therefore imperative to have a check-up with your dentist before starting a treatment to identify

  • sensitive teeth or gums, including sensitivity associated with gum recession or defective fillings (fillings, composites).

  • potential gingivitis, periodontitis or advanced caries.

Your dentist may place some temporary or permanent limitations.


In addition, thinning may be contraindicated in some cases.

  • People under 18 years of age because the pulp chamber is larger, therefore the teeth would be more sensitive during bleaching. 

  • Pregnant or breastfeeding women.

  • Fillings (fillings, composites), crowns or veneers cannot be bleached with peroxide. You should consider redoing these restorations after bleaching if the result leaves uneven shades.

5. Is the treatment supported by Health Insurances?

  • As with all purely aesthetic therapies, there is no expectation of reimbursement. Nevertheless, the preliminary scaling, if necessary, as well as the control visit of the oral cavity are covered at the social security rate.

6. How is the treatment and how to use of the gutter?

During the first visit, your dentist

  • performs an oral check-up in order to avoid initiating a treatment if there are contraindications (see Question 4 "contraindications"),

  • performs a rigorous scaling in order to remove plaque (biofilm) and tartar and thus allow the product to act directly on the enamel,

  • takes impressions of the teeth in order to make a custom-made mouthpiece.

During a second appointment, about a week after the first one and in any case less than a month after it to still benefit from the initial scaling, the patient comes back to the office to pick up his tray and the whitening product. He/she will receive the instructions for use (see below).

  • Brush your teeth, as the gel is much more effective on clean teeth.

  • Using the syringe, apply a small drop of gel (the size of a half-lens) inside the gutter on the side corresponding to the outer face of the teeth (never on the last tooth of the arch). Do not use more than ½ syringe for both arches.

  • Insert the gutter into the mouth and position it well on the teeth. Remove excess gel with your finger if necessary. If the excess is too important, rinse gently without swallowing, and plan to apply less the next day ...

  • Wear the gutters overnight if you can stand them.

  • The next day, remove the gutter, rinse your mouth thoroughly and clean the gutter with a soft toothbrush in cold tap water. Store the gutter in the provided case.

7. What are the precautions during teeth the bleaching treatment?

  1. Avoid coloring agents as much as possible (coffee, tea, cigarettes, red wine, tobacco, liquorice, tomato sauce, cherries, blueberries ...) especially during the 30 minutes following the removal of the gutter and if possible throughout the duration of the treatment and then during the following week, in order to optimize the results.

  2. Store the bleach away from direct sunlight and heat. Refrigeration recommended. Do not freeze.

  3. Do not swallow the gel or rinse aid. Products contain peroxide and may also contain fluorine; ingestion of large quantities of these products may be harmful.

  4. Keep the gel out of the reach of small children.

8. Minor or temporary effects of teeth whitening

  1. A small percentage of patients may experience sensitivity (to cold) with bleaching. If this is your case, space out the use of the gutter (every other night or every third night). In case of extreme sensitivity, stop the treatment and contact Dr Barral-Cadière who will prescribe a desensitizing gel. This gel would be placed in the gutter as the lightening product with a wear of only 10 minutes up to an hour in case of more severe pain.

  2. Foods and juices high in citric acid can cause sensitivities.

  3. Some patients have noticed temporary discomfort in the gums, lips, throat or tongue. If these symptoms persist for more than two days or worsen gradually, call your dentist. These side effects usually subside 1 to 3 days after stopping treatment.

  4. White spots on the enamel may appear during whitening. They will dissipate at the end of the whitening process.

  5. The teeth are naturally darker along the gum line. This area may require more time to lighten compared to the rest of the tooth surface and generally remains a bit darker.

  6. Some old amalgams or "silver" fillings can leave a dark purple mark in your whitening tray, this is normal.

8. Restore the symmetry of the smile

Professional teeth whitening products available through your dentist are dosed correctly.

1) Products sold directly to the consumer: the maximum concentration of hydrogen peroxide should not exceed 0.1%, which limits their effectiveness.
2) Products for dentists only: 0.1-6% hydrogen peroxide (6% of H2O2 corresponds to 18% carbamide peroxide). They need to be checked by your dentist to ensure their effectiveness and to avoid contraindications.
3) Products with a concentration of more than 6% are prohibited in the European Union Member States. This is because excessive doses of hydrogen peroxide can damage the mucous membranes and prolonged use of hydrogen peroxide can lead to reversible hypertrophy of the papillae of the tongue, also known as "black tongue".

Source:Direction générale de la concurrence, de la consommation et de la répression des fraudes 

10. Why does the color of teeth evolve?

The color of our teeth is linked to 2 parameters:

  • "internal": the thickness of the outer layer of the tooth, the white enamel, revealing more or less the dentin, the rather yellowish layer that lies under the enamel.

  • "external": the presence of colored molecules that are deposited on the surface of the teeth


This color can evolve with time because of yellowing factors:

  • The natural aging of the dentition which thins the white layer of enamel.

  • Diet

    • Acidic foods (fruit juices, especially citrus fruits, soft drinks, black coffee, tea, alcoholic beverages, salad dressing, etc.) can cause acid erosion, i.e., acidic exposure over long periods of time (without brushing), which thins and weakens the enamel layer and increases the porosity of the surface, which then favors the attachment of food particles

    • The tannins contained in certain beverages (coffee, tea, wine) or the coloring agents of certain sweetened beverages which can lodge in the micro-cavities of the enamel. Without appropriate treatment, these stains may settle deeper and be more difficult to remove.

  • Cigarettes, whose tar causes a yellow coloration and nicotine attacks the enamel.

  • Medication, especially certain antibiotics.

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