What is tooth whitening?
Tooth whitening lightens teeth and helps to remove stains and discolouration. Whitening is amongst the most popular cosmetic dental procedures because it can greatly improve how your teeth look, without removing any tooth structure. Tooth whitening through bleaching is one of the most common treatments used to whiten teeth and improve your smile.
Extrinsic and intrinsic staining
Every day, a thin coating (pellicle) forms on the enamel and picks up stains, and the tooth enamel contains pores that can hold stains.
There are two types of stains that affect the teeth: extrinsic and intrinsic. The extrinsic stain is caused by factors that affect the surface of the enamel, collecting in the pellicle that attaches to the tooth surface and includes the following:
- Using tobacco for smoking.
- Drinking dark-coloured liquids such as coffee, soft drinks, tea and red wine.
- Not taking good care of your teeth through proper brushing or flossing and allowing a build-up of plaque and calculus to collect on the tooth surface.
Aging makes teeth become less bright as their enamel gets thinner and their dentine becomes more visible. Dentine is naturally a darker colour than enamel.
Intrinsic stains are stains that occur within the tooth structure. The following are causes of intrinsic staining:
- Too much exposure to fluoride during childhood.
- Use of tetracycline antibiotics by expectant mothers during the second trimester of pregnancy.
- Use of tetracycline antibiotics by a child who is 8 years old or younger. Teeth are still developing during these years.
- Trauma or injury to a tooth may also darken it.
- Those factors causing extrinsic staining can also be absorbed into the enamel causing it to darken.
Tooth whitening is only effective on surface (extrinsic) stains unless you are using a bleaching agent. Tooth bleaching agents are effective for some intrinsic stains.
The outer layer of a tooth is called the enamel. The colour of natural teeth is created by the reflection and scattering of light off the enamel combined with the colour of the dentine under it. Your genes affect the thickness and smoothness of the enamel. Thinner enamel allows more of the colour of the dentine to show through. Having smoother or rougher enamel also affects the reflection of light and therefore the colour.
How tooth whitening through bleaching is affected by other dental issues
Other dental problems can affect the success of tooth bleaching. For example, cavities need to be treated before teeth are bleached. That's because the bleaching solution can pass through decayed areas and reach the inner parts of the tooth. If your gums have receded, the exposed roots of your teeth may appear yellow or discoloured. Whitening products will not make them significantly whiter.
If you have tooth decay or receding gums, bleaching may make your teeth sensitive. Whitening also does not work on ceramic or porcelain crowns or veneers.
The tooth whitening process
Whitening can be done in the dental office or at home. For in-office whitening, your dentist will probably photograph your teeth first. This step will help him or her to monitor the progress of the treatment. Your dentist will also examine your teeth and ask you questions to find out what caused the staining and if in-office whitening or at home whitening is right for you.
Next, the dentist or a dental hygienist will clean your teeth. This will remove the film of bacteria, food and other substances that build up on your teeth and contribute to the staining. Once this is done, the bleaching procedure begins.
For whitening at home through bleaching, your dentist can make trays that fit your teeth precisely to hold the whitening gel. Home whitening gel usually needs to be applied daily for two to three weeks. Over-the-counter kits also are widely available for home use. They provide trays to hold the gel or whitening strips that stick to your teeth. Talk to your dentist if you want to use these home products. Be sure to follow the directions to avoid overuse and possible damage to your teeth and mouth.
How it's done
There are two main types of teeth whitening procedures through bleaching. Vital bleaching is performed on teeth that have live nerves. Non-vital bleaching is done on a tooth that has had root-canal treatment and no longer has a live nerve.
The most common type of vital tooth bleaching uses a gel that is applied directly to the tooth surface. This product contains some form of hydrogen peroxide. Tooth whitening through bleaching can be done in the dentist's office or at home.
In-office whitening allows your dentist to use a more powerful bleaching gel. A specialised light or laser activates the gel and allows bleaching to happen faster. In-office whitening usually takes 30 to 90 minutes and will require 1 to 3 appointments. The number of treatments will depend upon the method used, how severe your stains are and how white you want your teeth to be. Different types of stains respond differently to the treatment .
First, your dentist will apply a substance that covers and protects the gums around the teeth. Then, the bleaching agent will be placed on the teeth.
Some bleaching agents are activated by a laser light or a curing light to activate the peroxide. After the whitening agent is applied, the dentist will shine the light on your teeth. If they are badly discoloured, your dentist may suggest that you continue the bleaching process at home for a few days or weeks.
For at-home whitening, your dentist will take impressions of your upper and lower teeth and will make custom mouth trays to fit you. The mouth tray needs to fit well. A close fit helps the bleaching agent remain in contact with your teeth.
At home, you will fill each mouth tray with a bleaching gel that your dentist provides. You will wear the mouth trays for the time period stated on the bleaching package. Many people achieve the amount of whitening they want within a week or two. However, you may need to wear the mouth tray for over four weeks or longer.
You also can buy whitening products over the counter. They contain a lower percentage of bleaching agent than the products you can get from your dentist. Therefore, whitening may take longer. The bleaching agent is applied as a gel placed in a mouth tray or as a strip that sticks to your teeth, or it can be incorporated into a toothpaste. Over-the-counter mouth trays fit less securely than the mouthpiece your dentist can custom-make for you.
Most whitening toothpastes contain abrasives that remove extrinsic stains on the enamel but it is possible to get a toothpaste that also contains hydrogen peroxide that can remove intrinsic stains over time.
Vital bleaching may not improve the appearance of a tooth that has had root-canal treatment because the stain is coming from the inside of the tooth. Root-filled teeth can discolour over time. If this is the case, your dentist will use a different procedure that whitens the tooth from the inside. He or she will place a bleaching material inside the tooth that has had a root canal filling, and the bleaching material will be left inside the tooth (or periodically replaced) until the tooth reaches its desired colour (shade). The bleaching material is then removed and the tooth is sealed with a composite filling.
If you find that your teeth or gums are irritated and sore after the treatment, follow up with your dentist.
Whitening is not a permanent solution and stains may come back. If you smoke or consume a lot of staining foods or drinks, you may see the whiteness start to fade in as little as one month. If you avoid these sources of staining, you may not need another whitening treatment for a much longer period.
Re-whitening can be done in the dentist's office or at home. If you have a custom-made mouth tray and whitening agent at home, you can whiten your teeth as often as you need to. Discuss your whitening schedule with your dentist. You can talk about which whitening products would work best for you.
Whitening is unlikely to cause serious side effects, although some people's teeth may become sensitive for a short period of time. You may get mild gum irritation after tooth whitening. Women should not have their teeth whitened while pregnant. Since the procedure is cosmetic, it should be postponed until after the baby is delivered.
Your best smile
Tooth whitening can be a positive experience for you if you are not happy with your current smile. Schedule an appointment with your dentist to discuss the at-home and in-office treatments that may be right for you so that you can obtain that aesthetically-pleasing smile.