In-practice or at-home whitening: what is the difference?
At the practice, the dentist applies the product in one or a few sessions. At home, you wear custom-made trays with a prescribed gel over a longer period. The two can be combined.
Teeth whitening
In-practice whitening uses a more concentrated gel, applied by the dentist after the gums have been protected. It gives visible lightening in a short time, generally in one or two sessions depending on the starting shade and the result you are looking for.
At-home whitening relies on trays custom-made from impressions of your teeth. You place a less concentrated gel in them and wear them at the pace indicated, often for one to a few weeks. The result is gradual and often well tolerated.
The two methods can be combined: a session at the practice to start the lightening, then trays at home to refine it or to maintain it later.
Products sold over the counter, outside dental supervision, should be approached with caution. Before any whitening, an examination checks that there are no cavities or gum problems, and the dentist tells you which method suits you.
This is a general answer. Only a consultation at the practice can tell what suits your situation.