Shade change is the number patients ask about first and the number the marketing pages answer least honestly. The peer-reviewed picture is narrower than the ads suggest but clearer than most patients realize.
What the trials actually measure
Whitening studies typically report change on the Vita Classical shade guide, re-ordered from lightest (B1) to darkest (C4). A change of 5 to 7 shade tabs is a common outcome for a course of 10 percent carbamide peroxide worn in custom trays over two weeks, according to the Cochrane Oral Health review of home-use tooth whitening.
In-office bleaching with higher-concentration hydrogen peroxide can produce a faster visible change in a single visit, but the six-month follow-up shade in comparative trials tends to converge with take-home tray results.
Why real-world results vary
The ADA notes that extrinsic stains from coffee, tea, red wine, and tobacco respond more predictably than intrinsic discoloration from tetracycline exposure, fluorosis, or age-related dentin darkening.
Restorations do not bleach. Crowns, veneers, and composite fillings keep their original color while surrounding enamel lightens, which is one of the most common reasons patients are disappointed after a whitening course.
A realistic expectation to set
For an adult with generally healthy enamel and extrinsic staining, a properly supervised course of tray-delivered carbamide peroxide can be expected to produce a visible lightening most observers will notice, with peak color typically settling about two weeks after treatment ends and gradual regression over 6 to 12 months.