In-office whitening lifts most patients three to eight shades in one ninety-minute session — but grey tetracycline staining barely moves, and here is why.
In-office whitening moves most patients three to eight shades on the standard shade guide in a single ninety-minute session. The gel is a hydrogen peroxide compound that diffuses through enamel and breaks the long-chain pigment molecules trapped inside dentine into smaller, less visible ones. It does not strip a layer off the tooth. Because the change happens inside dentine rather than on the surface, the result outlasts anything a polish or a whitening toothpaste can deliver.
Yellow and brown staining from tea, coffee, red wine and tobacco sits in the organic layer that peroxide attacks directly, so those cases respond fastest. Grey discolouration is a different problem. Tetracycline banding from childhood antibiotics, and the greyness of a tooth that has lost its nerve, are structural, and bleaching moves them barely at all. We check this at the assessment and say honestly when veneers, not whitening, are the only route to the shade you have in mind.
The light you see in whitening photographs contributes far less than the marketing suggests. Peroxide concentration, contact time and how well the barrier isolates the gel from your gums are what determine the outcome; the lamp mainly accelerates the early reaction and, at higher heat, increases sensitivity. We use it because it shortens chair time, not because it produces a whiter tooth. A clinic charging a premium for a specific lamp brand is charging you for the wrong variable.
An in-office session is €180 and takes about ninety minutes, including isolation of the gums and two or three gel applications. Expect the result to hold twelve to twenty-four months. Smoking, daily coffee, black tea, red wine and curry pull the shade back fastest, and the first forty-eight hours after the session are when enamel is most porous — so a white diet for two days genuinely matters. Home top-up trays extend the interval between sessions.
At the concentrations and contact times used in a supervised clinical session, no permanent damage has been demonstrated. Enamel does become temporarily more porous for a day or two, which is why we apply fluoride afterwards and ask you to avoid strongly coloured food and drink during that window.
Ceramic does not change colour, so whitening would only make the natural teeth around your crowns lighter and the mismatch more obvious. In that situation we tell you plainly that whitening is the wrong treatment for you.