It is not a good idea to do braces on teeth with veneers. Veneers are usually beautifully glazed (coated with a thin layer of glass) if they are made of porcelain to give a stain-resistant uniform surface. If the veneer is made of composite, the surface will have been carefully polished to give a beautiful shine. Whenever something needs to be glued on to a surface (a tooth surface or a veneer surface), the surface needs to be roughened.
This means that the glaze needs to be removed or the polished surface needs to be roughened (the shine is removed). Porcelain veneers nowadays are made without internal layers for colour but are surface tinted.
The process of surface roughening can also remove the surface tint, permanently changing the colour of the veneer. Once the orthodontic treatment is completed and the braces are removed, no amount of polishing can restore the original lustre of the porcelain glaze.
So unless the patient was planning on redoing the veneers afterwards, orthodontics should always come first. There are challenges with maintaining retention (keeping the teeth fixed in position) in between the braces coming off and the veneers going on. After the veneers are completed, retainers should be prescribed to maintain the alignment of the teeth and veneers.
