Teeth whitening is an aesthetic procedure in which peroxide-containing gels are applied under a dentist's supervision to lighten the natural color of the teeth. There are two main methods: in-office whitening, done at the dental office, and at-home whitening, continued at home with custom trays prepared by the dentist. For whitening to be applied safely, the teeth and gums need to be healthy beforehand.
What is teeth whitening?
Teeth whitening is a method in which gels containing hydrogen peroxide or carbamide peroxide are applied to the tooth surface to lighten the color pigments within the tooth structure. The procedure does not wear away the tooth surface; it aims to bring the tooth's own color to a lighter shade.
Peroxide passes through the enamel layer to reach the underlying dentin and breaks color-causing molecules into smaller, lighter-colored fragments. The shade that can be achieved depends on the natural structure of the tooth and the cause of the discoloration; for this reason, the expected result is not the same for everyone.
Whitening is different from removing surface stains caused by tea, coffee and smoking with a professional dental cleaning. A large share of stains are superficial; for this reason, tartar removal (scaling) is often recommended before whitening.
Why do teeth change color?
Changes in tooth color fall into two main groups:
- Extrinsic discoloration: Stains left on the tooth surface by tea, coffee, red wine, smoking and some mouth rinses.
- Intrinsic discoloration: Thinning of the enamel with age, trauma, changes after root canal treatment, certain medications taken while the teeth were developing, or excessive fluoride exposure.
The effect of whitening differs depending on the cause of discoloration. Yellowish tones generally respond better, while gray-brown discoloration related to certain medications may respond more modestly.
How is in-office teeth whitening done?
In-office whitening is performed at the dental office by the dentist using a higher-concentration gel. The procedure proceeds in these steps:
- The starting shade of the teeth is recorded and the teeth are cleaned.
- The lips and cheeks are held back, and the gums are covered with a light-cured protective barrier.
- The whitening gel is applied to the tooth surfaces and renewed at set intervals.
- At the end, the gel and barrier are removed and the shade achieved is evaluated.
In-office whitening usually does not require anesthesia. The result may be noticeable after a single session; however, the number of sessions needed varies depending on the starting shade and expectations. In some cases, in-office and at-home methods are used together.
Some in-office systems use special light sources to activate the gel. Scientific findings on whether light adds anything to the whitening result are debated; the choice of method is made based on the dentist's assessment. Throughout the procedure, care is taken to ensure that the gum barrier stays in place and that the gel does not touch the gums.
How is at-home teeth whitening done?
For at-home whitening, impressions of the teeth are taken first, and thin, clear custom trays are made. A small amount of gel at the concentration the dentist specifies is placed in the trays, which are worn for the recommended length of time.
With this method, the color change progresses more gradually, and the duration of use is set by the dentist. It is important to use a small amount of gel so that it does not overflow the tray and touch the gums, and to wipe away any excess. When over-the-counter products and ill-fitting trays are used without a dentist's supervision, the risk of gum irritation and sensitivity may increase.
Whitening toothpastes sold in stores and online are mostly designed to reduce surface stains and do not significantly change the internal color of the tooth. Long-term, frequent use of highly abrasive products can damage the enamel surface and exposed root surfaces. It is recommended that you consult your dentist before using any product.
Who is teeth whitening not suitable for?
Whitening is postponed or not recommended in the following situations:
- Pregnancy and breastfeeding (not recommended as a precaution)
- Under 18 years of age
- Untreated tooth decay, or broken or cracked teeth
- Active gum disease
- Root surfaces exposed by gum recession, and marked tooth sensitivity
- Known allergy to peroxide
- People with large fillings or crowns on their front teeth that may not match the new tooth color
Exposed root surfaces may be more sensitive to whitening gel. In this case, it may be appropriate to first consider gum recession treatment options.
Having these conditions does not mean that whitening can never be done. Whitening can be reconsidered after problems such as decay, gum disease or sensitivity have been treated.
Do fillings and crowns whiten?
No. Whitening gels affect only natural tooth structure; composite fillings, porcelain veneers, crowns and bridges do not whiten. If there are such restorations on the front teeth, a color difference may develop between the natural teeth and the restorations after whitening.
If you are planning fillings or crowns on your front teeth, it is recommended that whitening be done before the restorations. This way, the color of the new restoration can be chosen based on the tooth shade achieved after whitening. Existing restorations may need to be replaced later for color matching.
For a single root canal-treated tooth that has darkened from the inside, a different whitening method performed from inside the tooth may be considered. If comprehensive aesthetic changes are planned, they are evaluated together as part of smile design.
Will there be sensitivity, and what should you pay attention to after whitening?
Sensitivity to cold and heat during and after whitening is a common side effect. This sensitivity is mostly temporary and usually eases within a few days. When needed, your dentist may recommend desensitizing products or adjust the intervals between applications.
- In the first few days after the procedure, limit staining foods and drinks such as tea, coffee, red wine, cola and dark sauces.
- Do not smoke.
- Be careful with very hot and very cold foods.
- Keep up your oral care routine and attend your check-ups.
The color achieved with whitening may darken somewhat over time, depending on lifestyle habits. How long this takes varies from person to person; when needed, touch-up treatments can be planned under a dentist's supervision.
If sensitivity lasts a long time, you feel sharp pain in a particular tooth, or you notice whitening or burning of the gums, you should pause the treatment and see your dentist.
How are the gums protected during whitening?
When whitening gels stay in contact with the gums for a long time, they can cause irritation, whitening of the gum tissue or sensitivity. For this reason, in in-office treatment the gums are covered with a protective barrier; in at-home treatment, custom trays are used and the gel is kept from overflowing.
Periodontist Dr. Nadin Gemrekoğlu, DDS, PhD, considers it important to evaluate gum health before whitening; treating any gum inflammation first has a positive effect on both comfort during the procedure and the aesthetic result. If you notice bleeding or sensitive gums, see your dentist before whitening. The article on brushing and interdental cleaning can be a helpful guide for daily care.
