Causes of Tooth Discoloration
Discoloration falls into two groups, and this distinction determines whether whitening will work.
Extrinsic staining
Surface stains from coffee, tea, red wine, cola, smoking and some spices, plus plaque and calculus. These respond very well — sometimes professional cleaning alone is enough.
Intrinsic discoloration
Changes within the tooth: age-related dentine darkening, discoloration after pulp death or root canal treatment, childhood tetracycline use and fluorosis. Results vary; tetracycline staining usually improves only partially.
Surfaces that will not lighten
Composite fillings, veneers, zirconia crowns and bridges do not respond. If a patient has restorations on front teeth, whitening creates a visible mismatch — so either the restorations are also replaced or whitening is reconsidered.
Whitening Methods
There are two main methods, and combining them often gives the best result.
In-office whitening
A high-concentration gel is applied in the clinic after the gums are protected with a barrier. A visible difference is achieved in a single session, with slightly more sensitivity than the home method.
At-home whitening
Uses a custom tray made from your impression, with lower-concentration gel worn for a set time daily over a few weeks. Custom fit matters: ready-made trays let gel leak onto the gums.
Internal bleaching for root-treated teeth
Where a single tooth has darkened after trauma or root canal treatment, external whitening is inadequate because the change is internal; the agent is placed inside the tooth instead.
Ineffective and risky methods
Baking soda, lemon, vinegar and charcoal abrade the enamel. The temporary brightness is surface wear, and as enamel thins the yellow dentine beneath shows more — so teeth look yellower long term. Enamel does not grow back.
What to Expect After Whitening
Results vary between individuals, and setting the right expectation matters.
Sensitivity
Temporary cold sensitivity is common and normal, usually settling within days. Desensitising toothpaste before and after helps; for very sensitive patients the session is shortened or the home method preferred.
The first 48 hours
Enamel is temporarily more permeable and prone to staining. Avoid coffee, tea, red wine, cola, tomato and soy sauce, red fruits, beetroot and smoking for 48 hours.
How long results last
Whitening is not permanent; longevity depends on diet, smoking and hygiene. Top-up sessions are usually recommended periodically.
The Limits of Whitening and Alternative Approaches
Not every discolouration is solved by whitening; the source of the stain determines which approach is appropriate.
A Single Darkened Tooth and Internal Bleaching
When one tooth is noticeably darker than its neighbours, this usually relates to loss of vitality; changes in the pulp after trauma or deep decay darken the tooth from the inside. In this situation whitening applied to the outer surface will not give the expected result.
The status of the tooth's root canal treatment and the tissues around the root are assessed first. In suitable cases, internal bleaching, in which the agent is placed inside the tooth, may be considered. The outcome varies with the tooth's starting shade and how long it has been discoloured, so expectations are discussed beforehand.
Other Options According to the Type of Discolouration
For superficial white or brown marks, microabrasion, in which a very thin layer of enamel is smoothed, may be considered. Where the colour difference is limited to a small area, composite can be used to blend the shade. These methods are not substitutes for whitening but alternatives chosen according to the nature of the stain.
Where discolouration is widespread and resistant, or where tooth shape is also irregular, restorative options such as veneers or crowns come onto the agenda. Because these involve removing tooth structure they are irreversible, so the limits of less invasive approaches are considered first.
What Is Weighed When Choosing a Method
- Whether the discolouration lies on the enamel surface or within the tooth structure
- Whether there are fillings, crowns or bridges in the front region
- Whether there is wear, cracking or exposed root surface
- Gum health and the presence of any untreated decay
- Existing sensitivity levels and any previous whitening experience
- How far the daily habits maintaining the discolouration can be changed
- How long the result is expected to be maintained
Sensitivity and Safety in Whitening
The main reason whitening is carried out under professional supervision is to protect the tissues and manage sensitivity.
Why Sensitivity Occurs and How It Is Reduced
The short-lived sensitivity seen during and after whitening relates to the agent passing through enamel to the dentine and stimulating nerve endings. This sensation is usually temporary and settles quickly. Exposed root surfaces, worn enamel and existing cracks can make it more pronounced.
To reduce sensitivity, desensitising toothpastes may be recommended before and after treatment, and session length and frequency can be adjusted for the individual. Avoiding very cold and very hot food for a period also helps. If the complaint lasts for days or concentrates on one particular tooth, that tooth is assessed separately.
Protecting the Gum and Soft Tissue
In in-office applications the gum is isolated with a barrier so it does not contact the whitening agent. If contact does occur, a temporary whitish area and a burning sensation can develop; this usually resolves on its own within a short time. Correct isolation is therefore an inseparable part of the procedure.
With home systems, it matters that the tray is made from an individual impression; with ready-made trays the agent can overflow at the gum margin. Applying the prescribed amount for the prescribed duration helps prevent both gum irritation and unnecessary sensitivity.
Risks Seen With Unsupervised Products
- Products of unknown content and concentration roughening the enamel surface
- Agent overflowing at the gum margin with ready-made, non-custom trays
- Abrasive home remedies thinning enamel and making teeth look yellower
- Whitening over untreated decay and delaying the real complaint
- Failing to anticipate a colour mismatch with existing fillings and crowns
- Sensitivity that persists because of longer or more frequent use than advised
- The underlying cause of the discolouration never being investigated

































































