Why Do Teeth Become Discoloured?
Before choosing a whitening method, it helps to understand why teeth lose their brightness. Discolouration falls into two main categories: extrinsic staining (stains on the outer surface of the enamel) and intrinsic discolouration (staining within the tooth structure itself). These respond very differently to whitening treatment.
Extrinsic stains — the most common type — come from pigmented compounds in food and drink. Coffee, tea, red wine, turmeric, and tobacco are the biggest culprits. These stains accumulate on the pellicle (a thin film on the enamel surface) and respond well to both professional whitening and scaling/polishing. This is the kind of staining that most people are trying to address.
Intrinsic discolouration occurs within the dentin layer beneath the enamel. It can result from tetracycline antibiotic use during childhood (which causes greyish-brown banding), excessive fluoride during tooth development (fluorosis — white spots or brown patches), trauma to a tooth, or the natural yellowing of dentin with age. Intrinsic staining is much harder to treat and may not respond to standard whitening at all. Severe cases may require veneers or bonding instead.
First step: a professional clean
Before any whitening treatment, a professional scaling and polishing removes surface plaque and tartar. This alone can brighten your smile noticeably — and it's essential for even whitening results, since whitening gel cannot penetrate plaque or calculus deposits.
Professional In-Clinic Whitening
Professional whitening uses high-concentration hydrogen peroxide or carbamide peroxide gels (typically 25–40% concentration) applied directly to your teeth under controlled conditions. The dentist first places a protective barrier over your gums, then applies the whitening gel to tooth surfaces. A curing light or laser may be used to activate the gel and accelerate the whitening process.
The entire procedure takes approximately 60–90 minutes. Most patients see 6–10 shades of improvement in a single session. The primary advantages of in-clinic whitening are speed, intensity, and safety — your gums are fully protected, concentrations are precisely controlled, and any sensitivity is managed in real time.
Some patients experience temporary tooth sensitivity during or after the procedure. This typically resolves within 24–48 hours. Using a sensitivity toothpaste for a week before treatment reduces this significantly. Patients with existing dental work (crowns, veneers, fillings) should discuss realistic expectations with their dentist — whitening only works on natural enamel.
Dentist-Prescribed At-Home Whitening Trays
Custom-fitted whitening trays made from impressions of your teeth hold a lower-concentration whitening gel (10–22% carbamide peroxide) against your teeth for several hours per day, typically worn at night while you sleep. Results emerge over 2–3 weeks.
The key advantage over over-the-counter alternatives is the custom fit. A well-fitted tray ensures the gel contacts all tooth surfaces evenly and stays away from gum tissue. Ill-fitting generic trays allow gel to leak onto gums (causing irritation) and miss tooth surfaces (causing uneven whitening).
Custom at-home trays are excellent for gradual whitening with minimal sensitivity. Many dentists combine in-clinic whitening with at-home trays — a professional session for immediate impact, followed by at-home maintenance to refine and maintain results.
Over-the-Counter Products: What Actually Works?
Whitening toothpastes work primarily through mild abrasives that polish off surface stains. They cannot chemically bleach teeth. Some contain low concentrations of hydrogen peroxide or blue covarine (a pigment that creates an optical whitening effect). Results are subtle and slow, but they're useful for maintenance between professional treatments.
Whitening strips contain peroxide-impregnated plastic strips applied to front teeth. Results are real but limited — typically 2–4 shades over 2 weeks. They only cover the front teeth and don't conform to tooth curves well, often leaving unwhitened patches. Overuse causes sensitivity.
LED whitening kits sold online have flooded the market. Most use low concentrations of peroxide that are the same or lower than whitening toothpastes in effective bleaching power. The light itself has no significant whitening effect at home intensities. Many simply don't work as advertised.
Charcoal products are abrasive and can scratch enamel with repeated use. There is no clinical evidence that activated charcoal whitens teeth — and it may make them more susceptible to staining by removing the smooth, protective enamel surface.
Who Is a Good Candidate for Teeth Whitening?
Teeth whitening works best on patients with mild to moderate extrinsic or age-related yellowing. Healthy teeth and gums are a prerequisite — cavities and gum disease must be treated before whitening. Pregnant women should avoid whitening until after delivery.
Patients with heavily stained or intrinsically discoloured teeth (tetracycline staining, fluorosis) may achieve limited results from whitening alone. Veneers or composite bonding may be more appropriate for dramatic colour change in these cases.
Patients with multiple visible restorations (crowns, composite fillings on front teeth) should have a thorough consultation before whitening to understand which teeth will and won't respond, and whether replacements would be needed to match the new shade.
Maintaining Your Results
The "white diet" for the first 48 hours after whitening is important — avoid coffee, tea, red wine, curries, beetroot, and berries. Your enamel pores are slightly more open immediately after whitening and stain more readily. After 48 hours, normal foods are fine.
Using a straw for coffee and tea reduces direct contact with teeth. Rinsing with water after consuming staining foods helps. A whitening toothpaste used 2–3 times per week maintains results. A touch-up with at-home trays every 6–12 months keeps your smile bright long-term.