Teeth Whitening: Methods and Treatment Process
Teeth whitening (bleaching), uses dentist-supervised products containing hydrogen peroxide or carbamide peroxide to lighten discolouration within enamel and dentine through oxidation. This guide covers in-office and home whitening, the treatment process, possible side effects and aftercare.
What Is Teeth Whitening?
Teeth whitening works by breaking down stain molecules with hydrogen peroxide or carbamide peroxide . The active ingredient passes through enamel and acts on coloured molecules within the tooth, making its overall shade appear lighter.
Although whitening is a cosmetic procedure, healthy gums, teeth free of untreated decay and sound restorations are important prerequisites. It therefore begins with an assessment of oral health. Using unsuitable products without dental advice can cause tooth sensitivity or gum irritation.
Causes of Tooth Discolouration
Discolouration falls into two main groups:
External (extrinsic) stains
These arise from pigments on the tooth surface.
- Tea, coffee and dark-coloured drinks
- Red wine
- Tobacco products, including cigarettes and shisha
- Some spices and food colourings
- Plaque and tartar associated with inadequate oral hygiene
These stains often improve substantially after professional scaling and polishing ; bleaching may not always be necessary.
Internal (intrinsic) discolouration
This originates within the tooth structure.
- Age-related changes in dentine
- Exposure to tetracycline antibiotics during tooth development
- Fluorosis associated with excessive fluoride during tooth development
- Pulp damage after trauma or discolouration in a root-treated tooth
- Developmental changes affecting enamel or dentine
Some internal discolouration responds less well to external whitening; internal bleaching or restorative options may be considered where appropriate.
Whitening Methods
The method depends on the type of discolouration, clinical findings and the patient's preferences.
In-Office Whitening
The dentist protects the gums and applies a whitening gel. Product, concentration and application time follow clinical assessment and product instructions.
Sources and further reading
Sources consulted: 26 September 2026. These references provide general background; treatment decisions require an individual examination.
Dentist-Supervised Home Whitening
A suitable tray or dentist-recommended system is used at home. Your dentist explains the gel amount, wearing schedule and follow-up.
Combined Approach
In-office treatment may be followed by home whitening. This is planned individually on the dentist's advice.
Internal Bleaching
This may be considered for an internally discoloured tooth that has already had root canal treatment. After assessment, a bleaching material is placed inside the tooth behind a protective barrier and temporary seal, with follow-up visits as needed.
Treatment Process
Whitening begins with a clinical examination and proceeds in stages under dental supervision.
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Clinical examination
Decay, fillings, gum health, restorations and the type of discolouration are assessed.
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Scaling
Cleaning removes surface stains and helps establish whether whitening is still needed.
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Recording the initial shade
A standard shade guide, such as VITA, provides a baseline for reviewing the result.
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Whitening treatment
The agreed in-office or home method is used, with dental follow-up throughout the process.
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Managing sensitivity
The dentist may recommend products containing fluoride or potassium nitrate when appropriate.
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Review and maintenance
Aftercare advice is provided, and any future maintenance is planned according to individual need.
When Is Whitening Unsuitable?
Whitening is not suitable for everyone. Treatment may be postponed or alternatives considered in the following situations:
- Pregnancy or breastfeeding, when elective whitening is generally deferred because safety evidence is limited
- Children and adolescents, whose suitability and timing need specific assessment
- Untreated decay, leaking fillings or damaged restorations that need attention first
- Untreated periodontal disease
- Significant tooth sensitivity that needs to be managed first
- A known allergy to ingredients in the whitening product
Existing veneers, crowns and composite fillings do not change colour with whitening. Only natural tooth tissue is lightened, so a colour mismatch and possible replacement of visible restorations should be discussed beforehand.
After Teeth Whitening
Aftercare depends on the method used. Discuss habits that may contribute to staining or sensitivity:
- Frequent tea, coffee, red wine and strongly coloured foods can contribute to staining
- Tobacco use encourages discolouration
- Acidic drinks may aggravate sensitivity
Long-term shade maintenance is influenced by exposure to staining foods and drinks may affect shade maintenance. Review and professional cleaning intervals are based on individual oral health.
Advice on over-the-counter products
Whitening strips, gels and products bought online may cause tooth sensitivity or gum irritation . A dental examination helps identify existing problems and determine whether a product is suitable.
At a Glance
| Treatment type | Cosmetic dental procedure |
|---|---|
| Active ingredient | Hydrogen peroxide or carbamide peroxide |
| In-office duration | Varies with the method and individual plan |
| Home treatment duration | Days or weeks according to the product and dental instructions |
| Common side effect | Temporary tooth sensitivity |
| How long results last | Varies with individual factors, habits and care |
Frequently Asked Questions
Can whitening damage teeth?
Whitening is not risk-free. Temporary sensitivity and gum irritation can occur. Existing dental problems need assessment first; avoid excessive or incorrect product use.
Is whitening permanent?
A permanent result cannot be guaranteed. Colour may change again depending on diet, tobacco use, oral hygiene and tooth structure. Maintenance should be discussed with your dentist.
Does every type of discolouration respond?
No. Some tetracycline stains, severe fluorosis and trauma-related changes respond less predictably. Other approaches may be more appropriate.
Is sensitivity after whitening common?
Temporary sensitivity is common and often settles within a few days. Contact your dentist if symptoms are severe or persist; they may adjust treatment or recommend a desensitising product.
Can teeth be whitened during pregnancy?
Elective whitening is generally postponed during pregnancy and breastfeeding because safety evidence is limited. Discuss timing with your dentist.
How often can whitening be repeated?
There is no universal repeat interval. Your dentist assesses tooth condition, sensitivity and previous treatment before advising another application.
Do whitening toothpastes whiten teeth?
Many whitening toothpastes mainly remove external surface stains rather than substantially changing the tooth's underlying colour. Choose an appropriate product and avoid excessive abrasion or forceful brushing.
Information and examination appointments
Individual medical advice requires a clinical examination. You can use the contact page to request an appointment.