Teeth Whitening 101: Comprehensive Guide To Teeth Whitening

Published on 07 Jul 2021

Teeth whitening helps you achieve a healthier-looking, brighter smile

Whether you drink tea and coffee on the regular, or you are a smoker, chances are you worry about having yellow teeth. Teeth whitening is a dental treatment that helps you achieve a brighter and healthier-looking smile. It is a popular procedure that involves removing stains and lightening the colour of your teeth.

From in-clinic whitening treatments to store-bought whitening strips, there are many different whitening procedures out there and it can be hard to determine which is the most suitable for you. To help you understand teeth whitening procedures, we have put together a comprehensive overview on teeth whitening.

In this article, we will cover the following topics:

What causes teeth stains?

There are various causes of teeth stains (or teeth discolouration) and each type occurs due to different factors. Here, we explain the three main types of teeth stains:

Extrinsic stains

Extrinsic tooth stains occur on the outer surface of the tooth, known as the enamel. Tooth enamel covers and protects the softer part of the tooth, the dentin. Tooth enamel is exposed to everything that you eat and drink, which might contain pigments that leave a coloured residue. Over time, the accumulation of residual pigments can result in what appears to be yellow teeth, or even teeth stained by brown patches.

Drinking dark liquids like coffee can cause extrinsic stains

Drinking dark liquids like coffee, tea, Cola or red wine regularly is likely to cause extrinsic stains. Dark or highly-pigmented food, such as soya sauce, tomato sauce, balsamic vinegar or turmeric can also contribute to these surface stains. Smoking tobacco is also one of the culprits of stained teeth.

Since they occur on the surface, extrinsic stains are easier to treat than stains occurring deeper in the tooth. Brushing your teeth regularly with a whitening toothpaste that contains mild abrasives or bleaching agents (e.g. hydrogen peroxide) is a commonly-used method of removing these stains. However, whitening toothpastes are limited in their effectiveness, as some people find it hard to remove stubborn stains deeper within the tooth.

Intrinsic stains

Intrinsic teeth stains refer to stains that occur on the inner layer of the teeth, often the dentin. This happens when stain particles penetrate and build up deeper within the tooth. Intrinsic stains may be accompanied by symptoms that correspond with their cause, for example, a decayed tooth may look yellow, brown or even gray.

Here are several possible causes for such discolourations:

  • Dental trauma from an accident or fall
  • Genetic disorders
  • Overexposure to fluoride
  • Tetracycline (a type of antibiotic)
  • Tooth decay (caries)
  • Root canal treatment

Age-related stains

Most elderly adults find that their teeth discolour with age. Age-related teeth stains are a result of a combination of extrinsic and intrinsic stains. As you grow older, your teeth become more brittle, making your teeth prone to discolouration. Furthermore, the outermost layer of teeth enamel erodes over time and exposes the dentin, which naturally turns yellow with age.

How does teeth whitening work?

Since the tooth is semi-permeable, tooth whitening uses safe chemicals, namely hydrogen peroxide and carbamide peroxide, to permeate into the tooth enamel and break up stains into smaller, less visible components. This is how in-office teeth whitening treatments and take-home whitening kits usually work.

Whitening toothpaste, on the other hand, works slightly differently. They often contain a detergent material with particles that act as an abrasive to help physically remove stains on the outer surface of the teeth, without changing the actual teeth colour.

What teeth whitening options are there?

There is a wide range of teeth whitening options today. Here, we’ll explain the professional teeth whitening procedures offered by NTUC Health Denticare.

In-office teeth whitening treatment

In-office teeth whitening is an effective and safe way to get your teeth whitened. During in-office whitening treatments (or chairside teeth whitening), the dentist applies a professionally dispensed whitening gel on your teeth. The gel contains a high concentration of active ingredients and may be accompanied by the use of a light to speed up the action of the whitening agent. As a result, in-office treatments typically take less than an hour and are most likely to deliver reliable and noticeable results.

Take-home whitening kits

While both in-office whitening treatments and take-home kits involve a similar teeth whitening process, take-home whitening kits use whitening gels that are lower in concentration. They need to be applied multiple times for a teeth whitening effect.

The dentist will provide a custom mouth tray and prescription-strength gel kit. You can then easily administer the treatment at home by wearing the gel-filled bleaching tray at home, for 1 to 2 hours a day. Typically, results can be seen after 14 to 21 consecutive days of use. Bleaching trays and whitening gel refills can be purchased from our dental clinics too.

A bleaching tray being filled with prescribed whitening gel

A good time to use take-home teeth whitening is at night after thorough teeth brushing and before going to bed. Cleaning your teeth before using the whitening kit helps to prevent bacteria build-up. Additionally, giving your teeth a chance to rehydrate through the night while you are asleep helps to preserve the whitening results. You also reduce the chance of teeth staining as you won’t be eating during this time of the day.

In-office whitening treatment vs. take-home whitening kits

Both in-office treatment and take-home teeth whitening involve a similar procedure but differ with regards to several aspects. In the table below, we compare some of the pros and cons of both options.

In-office whitening treatmentTake-home whitening kit
  • Done in one session, with more predictable results
  • Safe administration by professional dentists
  • Gradual whitening results allow greater control over the desired shade
  • Can whiten teeth on your own schedule during non-office hours
  • Lower incidence of tooth sensitivity due to lower concentrations of active ingredients (e.g. hydrogen peroxide)
  • Pay for each visit
  • May be inconvenient to prepare bleaching trays and gels each time
  • Takes 2-3 weeks to reach the desired shade

Whitening toothpastes

Whitening toothpastes usually contain abrasive ingredients, such as silica, that polish the teeth by physically removing extrinsic stains on the surface. However, the natural colour of your teeth remains unchanged.

Some whitening toothpaste may contain small amounts of hydrogen peroxides or other chemicals that might help to dissolve stains. Blue covarine, a bluish pigment that adheres to tooth surfaces and changes the apparent colour of the teeth, might be found in some whitening toothpaste as well.

It typically takes several weeks before you might see noticeable whitening results, and in some cases, not at all.

Whitening strips

Whitening strips are plastic strips that contain a thin layer of whitening agent, often hydrogen peroxide or carbamide peroxide. Compared to chairside teeth whitening procedures, they use a lower concentration of these active ingredients. Just like take-home whitening kits, they can be administered at home by placing them on your teeth for a short duration of time.

While they are typically safe, using whitening strips too frequently or for extended durations may lead to side effects, such as increased tooth sensitivity and gum irritation. It is also important that you check the list of ingredients, as some may contain chemicals like chlorine dioxide that can potentially damage your teeth. We recommend you consult a dentist before you begin using teeth whitening strips.

Natural teeth whitening methods

There are many homemade teeth whitening remedies available on the internet. However, we caution against using such homemade whitening pastes, as they can cause permanent and irreversible damage to your teeth.

If you prefer to avoid teeth whitening procedures altogether, you can begin by adopting lifestyle habits that help to keep your teeth naturally white. One strategy is to prevent extrinsic stains by using a straw to consume drinks that contain tannins, pigments or high acidic content, such as coffee and red wine. Practising good oral hygiene and visiting your dentist twice yearly for checkups, scaling and polishing are also crucial in maintaining white teeth.

Porcelain Veneers

An illustration of how porcelain veneers work.An illustration of how porcelain veneers work.

Porcelain veneers (or more generally, dental veneers) are thin, tooth-coloured, custom-made shells that cover the front surface of your teeth. Veneering is an option for very extreme cases of multiple chipped teeth or intense discolouration that cannot be lightened by other methods. They are used to improve dental appearance and function by covering up stains or other imperfections on tooth surfaces. One tooth or multiple teeth may undergo veneering at the same time.

The veneering process may involve multiple visits to the dentist, as the porcelain veneers are made and applied on separate occasions. The dentist will first reshape the tooth surface, before making a model of the tooth, which will be sent to a laboratory for the veneer to be made. During your subsequent visit, the dentist will adjust the veneer before cementing it to your teeth.

How much does teeth whitening cost?

At NTUC Health Denticare, we offer in-office whitening services which start from $900 and take-home whitening kits from $500. The cost of the treatment is often determined by the extent of the stains to be corrected and the teeth whitening products used.

Refer to this table for a quick comparison of teeth whitening treatments offered by NTUC Health Denticare:

In-office whitening treatmentFrom $900.00
Take-home whitening kitFrom $500.00
Bleaching trayFrom $85.00 per arch
Whitening gel top-up$200

These prices are inclusive of GST and correct at the time of publishing. Please check with our clinics for the latest prices. For more information, you can read our article that compares the costs of teeth whitening treatments.

What happens after the treatment?

After the treatment, you should be able to immediately resume your daily activities. In some cases, patients may experience mild side effects like gum irritation, mouth ulcers or sore throat caused by the whitening ingredients, but these should subside fairly quickly.

Additionally, you should avoid the use of tobacco and limit your consumption of food and drinks that may cause extrinsic stains. You can consider drinking such beverages through a straw, and using a mouthwash or brushing your teeth right after consuming food and drinks that are likely to stain your teeth.

Aside from in-office whitening treatment, you may also consider purchasing a teeth whitening kit to maintain the results of your new smile in the long run.

How long does the treatment last?

The effect of teeth whitening treatments can last from several months up to 3 years, though this depends on your oral care and daily habits (e.g. regular consumption of coffee, tea or red wine).

While teeth whitening procedures help to reduce stains, they do not prevent future stains. To preserve the results of your teeth whitening treatment, you will need to practice excellent oral hygiene. This includes brushing and flossing your teeth regularly and visiting the dentist for cleaning and check-ups.

Potential concerns about teeth whitening

Is teeth whitening safe?

Yes, whitening treatment performed by a professional dentist is safe. Take-home teeth whitening kits purchased from your dentist are also safe to use, as long as you follow your dentist’s directions.

However, whitening toothpaste, strips and homemade bleaching agents may not be as safe, depending on their source and the ingredients they contain. Regardless of what whitening treatment you opt for, we recommend that you consult a dentist to determine if it is suitable for you.

Does whitening your teeth make them sensitive or weak?

Tooth sensitivity is a possible side effect of teeth whitening. It is typically caused by the bleaching agent used to whiten teeth. While it helps to remove stains, the bleaching agent also weakens the enamel by creating micro-sized holes. These holes may further expose the tooth’s nerves to sensations like extreme temperatures.

Tooth sensitivity is a common side effect of teeth whitening

Not everyone will experience sensitivity, but those who do are advised to avoid very hot or cold drinks for the first 24 hours. A desensitising gel, which is part of the teeth whitening kit, may be used to minimise sensitivity as well. You can also consider using toothpaste designed for sensitive teeth.

Is teeth whitening painful?

Teeth whitening is a safe and straightforward procedure that is typically painless when performed by a dentist. You will be able to resume your daily activities immediately.

What are the side effects of teeth whitening?

Possible side effects are temporary teeth sensitivity or a minor dull ache. Avoid very hot or cold drinks for the first 24 hours if there is any sensitivity and apply the desensitising gel provided in the take-home whitening kit.

Other common but short-lived side effects caused by the whitening ingredients include gum sensitivity, mouth ulcers and sore throat, though these should go away quickly.

If you have any concerns regarding the side effects of teeth whitening, speak to your dentist during your initial consultation.

How often should I whiten yellow teeth?

Illustration of excessive teeth whitening that may lead to gum irritation and bleeding

Whitening your teeth too often, whether at the dentist’s office or with whitening kits at home, can be harmful to your teeth. Too much of it can cause bleeding gums and damage tooth enamel, leading to increased tooth sensitivity or even damage to the nerves in the teeth. Some signs of excessive teeth whitening include gum irritation and redness, as well as increased sensitivity that does not subside. Your teeth might also start to appear translucent or “blueish”.

Follow the instructions provided by our dentist to avoid the side effects of overuse and transition to a plan to maintain the results of your teeth whitening.

Do teeth whitening procedures remove stains caused by tetracycline?

It is possible to lighten tetracycline stains with teeth whitening procedures. However, the results may vary across individuals, as it depends on the severity of the stains. It may not be possible to remove all the stains.

Is it suitable for pregnant women?

Teeth whitening is a safe procedure for pregnant or nursing mothers. It is not known to pose any risks to a developing foetus or nursing child.

Is it suitable for children?

We do not advise teeth whitening for children as their permanent teeth may not be fully developed and the procedure may damage their teeth.


At NTUC Health Denticare, our dentists will work closely with you to understand your lifestyle habits, learn about your teeth whitening goals and ensure that your teeth and gums are healthy for teeth whitening procedures.

Make an appointment today!

Call us at 6336 6222 or get in touch via our e-appointment form to book your appointment today!

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