Soothely
Composite does not whiten. Plan around it instead of hoping.
No whitening product on earth changes the colour of porcelain, ceramic or composite resin. That is not a failing of any particular gel, it is what those materials are. Understanding this before you start is the difference between a good result and a mismatched smile you have to pay to fix.
Whitening works by oxidising organic pigment molecules that have penetrated a porous natural tooth. Porcelain and ceramic are fired, glazed and non-porous. There is nothing for the gel to penetrate and no organic pigment trapped inside to break apart. Composite resin is slightly porous and can pick up surface stain, so cleaning it can restore its original shade, but the shade it was manufactured at is the lightest it will ever be.
If your dental work is currently lighter than your natural teeth, whitening closes the gap and usually improves the match. This is the common case for people who had a crown fitted years ago and whose natural teeth have darkened since.
If your dental work already matches your natural teeth, whitening will make your natural teeth lighter and leave the dental work behind, and you will notice. On front teeth this is very visible.
Whiten your natural teeth to the shade you want first, then have the dental work matched to the new shade. Doing it in the other order guarantees a mismatch, and a dentist cannot lighten existing porcelain.
Whiten first and complete the course. Wait at least two weeks after finishing, because the shade rebounds slightly and then settles, and matching to a shade that is still moving produces a poor result. Then book the restoration and have it matched to the settled shade.
If you are planning veneers or a crown in the next few months, tell your dentist you intend to whiten first. Most will actively prefer it.
Fixed brackets block the surface underneath, so that area does not whiten until they come off. The exposed surface around them does. The result is visible patches when the brackets are removed, which then even out over the following months but slowly. Most orthodontists suggest waiting until debonding.
Removable aligners are a different matter entirely. You take them out, so the whole tooth surface is exposed and there is no patching problem.
Speak to your dentist before starting if you have veneers on your front teeth that currently match, extensive bonding, a crown on a visible tooth, active decay, gum disease, or exposed root surfaces from recession. None of those rule whitening out, but they change what a good outcome looks like and how you should sequence it.