What actually makes teeth whiter
Genuine whitening works through oxidation. Peroxide-based gels penetrate the enamel and break down the larger, pigmented molecules that cause discolouration into smaller, lighter fragments, so the tooth itself becomes brighter rather than merely cleaner on the surface.
This is the key difference from whitening toothpastes, which rely on mild abrasives to polish away surface deposits. Polishing helps with everyday staining, but it cannot change the underlying shade of the tooth.
In-clinic whitening
In-clinic whitening applies a higher-concentration gel under controlled, supervised conditions, often giving a visible jump in shade within a single appointment of roughly 60 to 90 minutes. It suits patients who want a fast result, or who are combining whitening with a short trip abroad.
Take-home trays
Custom-made trays, moulded precisely to your teeth, hold a professional-grade gel that you wear for a set time each day over one to two weeks. Because the trays fit exactly, the gel stays on the teeth and off the gums, giving even, controlled results.
Many patients combine both: an in-clinic session for an immediate lift, then trays for fine-tuning and later top-ups.
Why a dental exam always comes first
Whitening over an untreated cavity, a cracked tooth or inflamed gums can be uncomfortable and gives patchy results. A proper exam checks for these issues and also identifies whether your staining is extrinsic, sitting on the surface from coffee, tea or tobacco, or intrinsic, living deeper inside the tooth, which may respond less to standard bleaching.
What whitening cannot do
Whitening only lifts the colour of natural enamel. Crowns, veneers and fillings keep the shade they were made in, so if you are planning any of these on visible teeth, the usual sequence is to whiten first, let the shade settle for a couple of weeks, then have the new restoration matched to the final result.
Keeping your results
Results typically last from several months to a couple of years, depending far more on your habits than on the product used. Rinsing after coffee, tea and red wine, keeping up daily brushing and interdental cleaning, and using take-home trays for occasional top-ups all help preserve your shade for longer.