Teeth whitening (also called tooth whitening) is a cosmetic dental procedure that helps restore teeth that have become dark, yellow, or stained to a whiter appearance. It uses whitening agents containing hydrogen peroxide or carbamide peroxide. These whitening agents react with the pigments in the teeth, breaking them down and making the teeth appear whiter.
Over time, our teeth can become discolored due to many factors, including both what we consume and changes within the structure of the teeth themselves. Teeth whitening has therefore become a very popular way to restore a bright, attractive smile.
Main Causes of Tooth Discoloration
The main causes can be divided into two categories: external factors and internal factors.
External Factors
These are caused by stains that build up on the outer enamel surface of the teeth. In most cases, they come from foods and drinks such as tea, coffee, dark-colored beverages, strongly pigmented foods, curries, sauces, and berries. Stains from smoking can also make teeth look yellow.
Internal Factors
These causes originate from within the tooth structure itself, so they are usually more difficult to treat than external stains. As we age, the enamel layer, which is whiter, becomes thinner, making the naturally yellowish dentin underneath more visible. In addition, if a tooth becomes non-vital due to severe trauma or deep decay reaching the nerve, the blood vessels and nerves inside the tooth die, causing the tooth to appear darker. Certain antibiotics, especially tetracycline, if taken while the teeth are developing in childhood, may also cause permanent gray or brown discoloration within the tooth structure.
How Does Teeth Whitening Make Teeth Whiter?
Teeth whitening works because the whitening agents contain hydrogen peroxide or carbamide peroxide, which react with oxygen when they come into contact with the tooth surface. This process breaks down the colored compounds attached to the teeth into smaller particles that can then be removed. Whitening agents can also penetrate deeply into the tooth, helping reduce internal stains.
If whitening is performed at a dental clinic, the dentist may use a light to accelerate the whitening reaction, allowing the teeth to become whiter more quickly than with at-home treatment.
The results of teeth whitening typically last around 6 months to 1 year, depending on each person’s oral care habits, such as brushing properly, avoiding dark-colored foods and drinks like tea, coffee, wine, and soy-based stews, and refraining from smoking.
What Types of Teeth Whitening Are Available?
The two most common in-office whitening systems are:
- Cool Light LED
- Zoom
Cool Light LED Teeth Whitening
Cool Light LED whitening is a popular in-clinic whitening method because it is effective. It works by using cool LED light to activate the whitening gel, helping speed up the breakdown of stain molecules within the enamel and making the teeth appear whiter.
Zoom Teeth Whitening
Zoom whitening is also a popular in-clinic whitening method. It is a newer technology from the United States. It contains ACP, which helps reduce tooth sensitivity, and it can lighten teeth by up to 8 shades, because the whitening gel used in the Zoom system is more concentrated.
Types of Teeth Whitening Treatments
Teeth whitening can be divided into two main categories:
- Professional teeth whitening at the clinic
- At-home teeth whitening using equipment provided by the dentist, following the dentist’s instructions
Other Whitening Options
Internal Bleaching for a dark non-vital tooth
This is whitening performed from inside the tooth to treat a single darkened tooth that has died. Regular whitening cannot correct this problem. This method must only be performed by a dentist after root canal treatment has been completed.
Combined Treatment for severely discolored teeth
This provides the highest level of whitening and is suitable for people with especially dark teeth. Treatment usually begins with in-office whitening for a quick initial result, followed by a take-home whitening kit to continue at home for a whiter and longer-lasting outcome.
Over-the-counter whitening products
These products have a lower concentration of whitening agent and may not provide very good results. For safety and the best outcome, you should always consult a dentist first, because if you have cavities or gum inflammation, using these products may cause severe tooth sensitivity or gum irritation.
In-office whitening has the advantage of being fast and producing quick visible results. The whitening gel is stronger and the procedure is closely supervised by a dentist. It usually takes only about 1 hour, making it suitable for people with limited time or who need quick results. The disadvantage is that it is more expensive, and the whitening effect may not last as long as at-home treatment.
At-home whitening uses a lower concentration whitening gel. It usually requires about 2 hours per day for 1–2 weeks to achieve the desired result. However, the advantages are that the whitening tends to last longer and the cost is lower.
If the teeth have heavy staining, both methods can be combined: whitening at the clinic first, then continuing at home.
Steps of In-Office Teeth Whitening Performed by a Dentist
The dentist compares the patient’s desired tooth shade before whitening.
- The dentist examines the patient’s oral condition, reviews their history, and compares the shade at both the neck and edge of the teeth.
- If necessary, some patients may need polishing or scaling first.
- Gum and lip protection is placed.
- A protective gel is applied to the gums and then cured with light. This step is very important because the whitening gel should not come into contact with the gums or lips.
- The whitening gel is applied to the teeth.
- A whitening light is used to activate the gel, helping it work more effectively and quickly.
- The light is applied 3–4 times, with each session lasting about 15 minutes.
- Once completed, all equipment is removed.
Steps for At-Home Teeth Whitening
Before whitening at home, the patient must first visit the dentist for a general oral examination to make sure the mouth is healthy enough for whitening. If there are cavities, inflamed gum pockets, or heavy tartar buildup, these must be treated first.
Once treatment is completed, the dentist will make a custom whitening tray, and the steps for home whitening are as follows:
- Visit the dentist to check whether the teeth are ready for whitening.
- Have an impression taken to make a custom whitening tray.
- Always brush your teeth before whitening.
- Place the whitening gel into the tray by gently squeezing it into the areas that will touch the front surfaces of the teeth. We are not whitening the entire tooth, only the front surface. Apply a small dot about the size of a match head in the center of each tooth area in the tray. The two very back molars do not need gel because they are not visible.
- Apply gel to both the upper and lower trays, about 8–10 teeth per tray.
- Wear the trays for about 2 hours.
- When finished, remove the trays and rinse your mouth thoroughly to clean away any remaining gel.
At-home whitening usually takes about 2 hours per session, and the whitening equipment, such as the tray and gel, should only be provided by a dentist for patient safety.
One tube of whitening gel can usually be used about 6–7 times. Using too much gel does not make the teeth whiter. If too much is used, it may overflow onto the gums and cause inflammation.
Preparing Before Teeth Whitening
- Clear any oral problems first. If you have cavities, tartar, or gum inflammation, these should be treated before whitening.
- Eat sufficiently beforehand. Whitening takes about 45–60 minutes, and you may experience mild sensitivity afterward. You will also need to avoid strongly colored drinks after treatment.
- Brush and floss thoroughly before your whitening appointment to remove food debris, which helps the whitening agent contact the tooth surface more effectively.
Symptoms After Teeth Whitening
The most common side effect is tooth sensitivity, which may occur shortly after whitening but usually goes away on its own within 1–2 days. However, if the sensitivity is severe or persistent, you should consult your dentist.
You may also develop gum irritation if the whitening agent comes into direct contact with the gums. Symptoms may include redness, swelling, inflammation, or bleeding. Treatment may involve cleaning the affected area or using medication.
Advantages of Teeth Whitening
The benefits of teeth whitening include:
- It makes the teeth whiter, sometimes by several shades depending on the original tooth color.
- It increases confidence by giving you a cleaner, brighter smile.
- It enhances your appearance, as whiter teeth can make the face look fresher and more attractive.
- It has less effect on the tooth structure than veneers.
- It can be used for patients with fluorosis-like white spots or mottled teeth.
Disadvantages of Teeth Whitening
The most obvious disadvantages include:
- Tooth sensitivity, which is common and may occur both during whitening and for about 1–2 days afterward. Brushing with desensitizing toothpaste may not help much because toothbrushing only lasts a few minutes before rinsing.
How to manage it: Put desensitizing toothpaste into your whitening tray. If one area is especially sensitive, place more toothpaste in that area, then wear the tray for 1–2 hours. This often works much better.
- Gum irritation, usually caused by using too much whitening gel, which then contacts the gums. A small amount of contact may happen, but you should try to avoid too much. In some people, excessive contact causes significant irritation. You can use a cotton bud (cotton swab) to wipe away excess gel.
- If you are still experiencing irritation even after using less gel, you can reduce the whitening time, for example to 1 hour per session.
- Some patients may notice excess saliva, but there is no need to worry. The saliva produced during whitening is safe to swallow. This usually lasts only 2–3 days and then returns to normal.
- Teeth whitening results are not permanent, so touch-ups are needed over time.
How to Care for Your Teeth After Whitening So the Results Last Longer
- Avoid dark-colored foods and drinks such as tea, coffee, wine, soft drinks, and deeply colored fruits, as these can cause the teeth to darken again more quickly.
- Brush properly using a fluoride toothpaste to strengthen the teeth and help prevent cavities.
- Floss daily to clean between the teeth.
- Visit the dentist regularly for oral check-ups and professional advice on how to care for your teeth properly.
- Use a fluoride mouthwash, which can help prevent cavities and maintain a brighter smile.
- Avoid smoking, as smoking can make the teeth yellow.
Who Is a Good Candidate for Teeth Whitening?
Teeth whitening is suitable for people who are unhappy with the color of their teeth, such as those with yellow teeth, dark teeth, or teeth that do not appear bright and clean. It is also suitable for people who care about their smile and appearance.
- People who drink tea or coffee regularly
- Heavy smokers
- People whose teeth have yellowed due to antibiotics
- People whose profession requires an attractive smile and good appearance
Who Is Not a Good Candidate for Teeth Whitening?
Some groups may not be suitable for teeth whitening or should avoid it because of possible side effects or unsatisfactory results, such as:
- Children and teenagers – In general, children under 16 years old should not undergo teeth whitening because the tooth nerves are not fully developed, which increases the risk of sensitivity or damage to the tooth structure.
- Pregnant or breastfeeding women – Whitening is not recommended because there is not enough evidence to confirm its safety.
- People with unhealthy teeth and gums – Those with gum problems or cavities may experience more irritation from whitening agents.
- People with dentures or artificial teeth – Materials used in dentures do not respond to whitening agents the same way natural teeth do, so whitening may be ineffective or make the tooth color uneven.
- People who are sensitive to whitening agents – Some people may be sensitive to ingredients such as hydrogen peroxide, which may cause irritation or allergic reactions.
- People with uneven enamel surfaces
- People with large fillings in the front teeth or crowns/veneers on some front teeth, because whitening may result in uneven tooth color
How Much Does Teeth Whitening Cost?
| Item | Price (THB) |
| In-office Cool Light teeth whitening (Cool Light Teeth Whitening System) | 5,500 |
| In-office Zoom teeth whitening (Zoom Teeth Whitening System) | 9,500 |
| At-home whitening with Opalescence (Opalescence Home Gel Teeth Whitening) | 6,500 |
Note: Please confirm the price with your dentist again, as promotions are offered frequently.
Frequently Asked Questions About Teeth Whitening
Can I whiten my teeth while wearing braces?
Teeth whitening can be done for both people with and without braces. However, if you are currently wearing braces, it is recommended that you complete orthodontic treatment first and then wait 3–6 months before whitening. Whitening during orthodontic treatment is not recommended because the teeth may move, which can lead to uneven results. In addition, the whitening agent may not be able to reach the areas covered by the brackets. Once the braces are removed, the tooth color may look uneven.
Does teeth whitening really make teeth thinner?
Teeth whitening uses products containing hydrogen peroxide, a whitening agent that does not react with inorganic structures such as enamel or the tooth surface. Therefore, it does not erode the teeth or make them thinner. However, the whitening agent can affect soft tissues in the mouth, such as the gums or inner cheeks, so protective gel must be applied to those areas to prevent irritation. Teeth whitening does not make teeth thinner.
How many times do I need to whiten my teeth?
This depends on the type of whitening:
- In-office whitening is generally done in a single visit, although 1–2 additional sessions may be needed for a whiter result. Each visit may take about 30–60 minutes.
- At-home whitening can be done multiple times according to the dentist’s instructions. Typically, it is done 2–3 times per week for 2–4 weeks, about 2 hours per session.
The results of teeth whitening usually last about 6 months to 1 year, depending on each person’s oral care. If you take very good care of your teeth, the whitening may last longer.
Is teeth whitening painful?
Teeth whitening is generally not painful, although mild sensitivity may occur in the first few days because the whitening agent breaks down the pigments attached to the tooth surface. This sensitivity usually goes away on its own within 1–2 days.
However, people with cavities, inflamed gums, chipped teeth, or cracked teeth may experience more severe sensitivity. Therefore, you should consult your dentist before whitening so any problems can be treated first.
How long do teeth whitening results last?
In general, the results last about 1 year, but this depends on many factors such as your diet and the drinks you consume. At-home whitening tends to last longer and can produce a whiter result than in-office whitening, although in-office whitening gives faster visible results.
Can I whiten my teeth before getting braces?
Yes, you can whiten your teeth before getting braces because teeth whitening itself is not directly related to orthodontic treatment. However, you should consider whether it is really necessary. Once braces are placed, the brackets will cover part of the tooth surface, so it may be difficult to notice the whitening result. Orthodontic treatment also takes a long time, usually 1–2 years or more, and after the braces are removed, you may need to whiten your teeth again anyway, which could mean paying twice.
