Teeth whitening is a cosmetic treatment that lightens the natural colour of your teeth using a bleaching gel, usually based on hydrogen peroxide or carbamide peroxide. It works on natural tooth enamel, not on crowns, veneers or fillings.
The safest way to whiten is under the guidance of a dental professional. Safe professional teeth whitening starts with a check-up to make sure your teeth and gums are healthy and that whitening will actually help with the type of staining you have.
Many people see a noticeably brighter smile, but professional whitening results vary. Some stains respond well, while others barely change. Teeth whitening sensitivity is the most common side effect and is usually temporary. This guide from Tomken Dental in Mississauga explains what causes staining, the options available, how professional whitening works, its risks and how to keep your results.
What Causes Tooth Discolouration and Staining?
Tooth discolouration comes from two main sources: surface stains on the enamel (extrinsic) and changes inside the tooth (intrinsic). Knowing which type you have helps predict how well whitening will work.
Extrinsic (surface) stains
These sit on the outer enamel and often respond well to whitening. The American Dental Association lists common causes of surface staining, including:
- Coffee, tea and red wine.
- Tobacco.
- Dark-coloured foods and drinks.
Intrinsic (internal) stains
These come from within the tooth and can be harder to lighten. Causes include:
- Aging: enamel thins over time, letting the yellower dentin underneath show through.
- Trauma: a knock to a tooth can cause it to darken.
- Medications: some antibiotics taken while teeth are developing, such as tetracycline, can cause grey or banded staining.
- Excess fluoride in childhood: this can cause white or brown marks (fluorosis).
What whitening can and cannot change
Yellow tones usually respond best. Brown tones respond less predictably, and grey tones may not lighten much at all. Whitening does not change the colour of crowns, veneers, bonding or fillings. This matters if you have visible restorations at the front of your mouth.
What Are the Different Teeth Whitening Options?
The main teeth whitening options are in-office whitening, dentist-supervised take-home trays, over-the-counter products and whitening toothpastes. They differ in strength, supervision, speed and cost.
| Option | How it works | Supervision | Typical considerations |
| In-office whitening | Higher-strength gel applied at a dental clinic with gums protected | Dental professional | Results in fewer visits |
| Take-home trays from your dentist | Custom-fitted trays with professional gel worn at home | Dentist-guided | Gradual results over days to weeks; trays can be reused for touch-ups |
| Over-the-counter strips and kits | Lower-concentration gel in strips or generic trays | None | Less predictable fit and results |
| Whitening toothpaste | Mild abrasives remove surface stains | None | Does not change natural tooth colour |
Generic trays and strips can let gel touch the gums, which may cause irritation. Custom trays from your dentist are shaped to your teeth to hold the gel where it belongs. Our article comparing in-office and at-home whitening goes into more detail.
In Canada, Health Canada sets safety requirements for tooth whitening products containing peroxide. Check the label and follow the directions for any product you use.
How Does Professional Teeth Whitening Work?
Professional teeth whitening uses a peroxide gel that breaks down into oxygen molecules. These move into the enamel and break apart the stain molecules, so the teeth look lighter. A dental professional controls the strength, timing and fit.
Step 1: Dental examination
Your dentist checks for decay, gum disease, worn enamel, cracks and existing restorations. Problems such as cavities or gum disease should be treated first. A professional Dental Cleaning in Mississauga before whitening can remove surface build-up so the gel works more evenly.
Step 2: Recording your starting shade
Your current tooth shade is noted so you can compare results.
Step 3: Whitening
- In-office: the gums are protected with a barrier, then gel is applied to the teeth for set periods.
- Take-home: impressions or scans are used to make custom trays. You wear them with professional gel for the recommended time each day.
Step 4: Review
Your dentist checks your progress, how your teeth feel and whether another round or a touch-up is needed.
The type of staining, your natural tooth colour and how closely you follow instructions all affect results. They are not permanent.
What Are the Risks and Side Effects of Teeth Whitening?
The most common side effects of teeth whitening are temporary tooth sensitivity and gum irritation. Health Canada states that home whitening products are not harmful when used as directed, and notes that they can cause sensitivity in some people, which is usually temporary.
Tooth sensitivity
Teeth whitening sensitivity happens when peroxide reaches the inner layer of the tooth and irritates the nerve. It usually feels like short, sharp twinges, especially with cold drinks. It tends to settle once whitening stops. To manage it, your dentist may suggest:
- A desensitizing toothpaste before and during treatment.
- Shorter wear times or days off between sessions.
- A lower-strength gel.
Gum irritation
Gel that touches the gums can cause temporary soreness or white patches. Well-fitting trays and careful application reduce this risk.
Uneven results
Restorations will not change colour, so they may not match your newly whitened teeth. Some stains lighten unevenly.
Overuse
Using whitening products too often or for too long can irritate the gums and teeth. Health Canada advises not using home whitening products for more than 14 days without supervision by a dental professional, and not more often than every six months.
Who should avoid or delay whitening
Health Canada advises against using tooth whiteners if you are pregnant, have mouth or gum disease, or have teeth stained by medication. Speak with a dentist first if you:
- Have untreated cavities or mouth infections.
- Have very sensitive teeth or exposed roots.
- Have had recent dental work.
- Are a child or teenager.
How Can You Maintain Your Results After Teeth Whitening?
You can keep whitening results longer by limiting staining foods and drinks, keeping up good oral hygiene and having occasional touch-ups as your dentist advises.
Limit staining foods and drinks
Coffee, tea, red wine, cola and dark sauces can re-stain teeth. You do not need to give them up, but rinsing with water afterward or using a straw for cold drinks can help.
Avoid tobacco
Smoking and vaping products are a major cause of yellow and brown staining.
Keep up good oral hygiene
Brush twice a day with fluoride toothpaste and clean between your teeth daily. Plaque picks up stains easily.
See your dentist regularly
Professional cleanings remove surface stains and tartar that dull your smile.
Touch-ups
Results gradually fade. With take-home trays, you can often do short touch-ups using fresh gel. Ask your dentist how often is safe for you.
When whitening is not enough
If whitening cannot reach the result you want, or if you have stains that do not respond, your dentist may discuss other cosmetic options such as Veneers & Same-Day Veneers in Mississauga or Dental Bonding in Mississauga.
Teeth Whitening at a Mississauga Dental Practice
A dental check-up before whitening helps make sure the treatment is safe and suited to your teeth.
If you are looking for a Dentist in Mississauga,Tomken Dental offers Teeth Whitening in Mississauga as part of our Cosmetic Dental Care in Mississauga. We provide take-home professional whitening with custom trays made for your teeth. If you are prone to sensitivity, we may suggest a sensitivity toothpaste for two weeks before you start, shorter wear times or a lower-concentration gel. Crowns, veneers and bonding will not lighten, and if you need a cleaning or treatment for cavities or gum disease, we schedule that before whitening begins.
For pricing factors, see our guide to teeth whitening cost in Mississauga. Call us to confirm suitability and appointment availability.
Frequently Asked Questions
How long does professional teeth whitening last?
Professional whitening results can last from several months to a few years. Your diet, tobacco use, oral hygiene and natural tooth colour all affect how long. Touch-ups can help maintain your shade.
Is professional teeth whitening safe for your teeth?
Professional teeth whitening is generally considered safe when a dentist checks your mouth first and the product is used as directed. Temporary sensitivity and gum irritation are the most common side effects.
What is the difference between professional and at-home teeth whitening?
Professional whitening uses stronger gels and custom trays or in-office application under a dentist’s guidance. Over-the-counter products use weaker gels with a generic fit and no professional check. Professional options tend to give more predictable results and help keep gel off the gums.
Can teeth whitening cause tooth sensitivity?
Yes, teeth whitening can cause temporary sensitivity. It usually fades after treatment stops. A desensitizing toothpaste, shorter sessions or a lower-strength gel can help.
Who should avoid teeth whitening treatments?
People who are pregnant, have gum disease, untreated decay, mouth infections or very sensitive teeth should avoid or delay whitening until they have spoken with a dentist. Whitening also will not change crowns, veneers or fillings, and may not work on medication-related stains.
A Brighter Smile, the Safe Way
Teeth whitening can make a real difference to how your smile looks, as long as it suits the type of staining you have and your teeth and gums are healthy. Professional guidance helps you get more predictable results with fewer side effects.
Thinking about whitening your teeth? Book a check-up so we can assess your teeth, explain what results to expect and recommend the safest option for you. Contact us to ask about teeth whitening and appointment availability.
This article is general information, not dental advice for your situation. Speak with a dentist before starting any whitening treatment.