IThe only veneers that are considered a "reversible" procedure would be a "No-Prep" Veneer. Technically you could remove a no-prep veneer and get back to your virgin tooth structure. Crowns are not "Reversible". I am assuming by your question when you say "Can veneers and crowns be removed" that this is what you're getting at. There are ways to ENSURE you'll like them before getting them bonded in place. On our website, you can see our process for placing veneers which includes 1) Diagnostic wax-up (which you're involved in the process) for picking the general look , length and shape, etc. 2) Temporaries that you wear: This "look" of the temporaries is predicated from the diagnostic wax-up (another process you're involved in). 3) The try-in of the permanent restorations (veneers or crowns) with try-in paste BEFORE they're bonded in place.
ALL 3 of the aforementioned steps help ENSURE you'll love the new look of your investment.
Hope this helps
Peter D Boulden, DMD, FACE, FIADFE, FAGD
3189 Maple Drive NE
Atlanta, GA 30305