Should I have whitening before veneers or crowns?
Often yes, if the remaining teeth need to match the new ones. Whitening has no effect on ceramic or composite, so it is done before their shade is chosen.
Teeth whitening
Whitening products lighten natural enamel, but not restorative materials such as ceramic, the composite of veneers or old fillings. A crown fitted today will keep its shade, even if you whiten your teeth later.
When only a few teeth are going to receive veneers or crowns, it is therefore often sensible to whiten the other teeth first. The shade of the new restorations is then chosen to match this new smile.
After whitening, it is usual to wait a little, often one to two weeks, before choosing the final shade and bonding, while the colour settles.
If you already have visible crowns or fillings, the dentist will point out that they may look darker after whitening and may need replacing to keep a harmonious result.
This is a general answer. Only a consultation at the practice can tell what suits your situation.