porcelain veneers over crowns and dental implants

For the conditions you describe such as enamel erosion, yellowing and a narrow arch, porcelain veneers are an excellent choice. Building out the bicuspids and molars will not only give you a wider smile, but also can improve facial and lip support. Placing veneers over existing implants and crowns may not make much sense since the cost of making a new crown for these teeth may be a similar cost, and bonding a veneer over an existing crown is never as good as a new crown. Finally, coordinating your treatment with veneers, implants and crowns is important and can be done simultaneously depending on the clinical conditions. 

While a Porcelain Veneer CAN be placed over an existing crown, that might not give you the best cosmetic result. You might be better off replacing the crown, whether it is over a natural tooth, or whether it is over an implant, with a new Porcelain Crown. And yes, you should do ALL the Porcelain Veneers and Porcelain Crowns at the same time, to get the maximum esthetic benefits.

Veneers, crowns, and implants can all be used in combination to create amazing results for a new smile.

Typically veneers or crowns are not placed "over" existing dental work. A lot depends upon what's already been worked on. 

You have already discovered the benefits of a smile makeover- that it can change the look of your face (remove wrinkles and tighten face sagging).

To get the best results, first meet with an experienced cosmetic dentist. To get the specific types of improvements you are asking about requires a lot of skill, artistry and experience. Many dentists and specialists can put in the implants or make a veneer, but to get all of the benefits you are asking about will require better than average planning and execution.

Have a great cosmetic dentist review your list of goals. Let him look at what there is to work with, and he will guide you on the most conservative way to get those results.

Do NOT begin ANY of this treatment until you have found the right dentist who will build the final cosmetic look. 

Dear Gerry,

What you are contemplating is a full mouth reconstruction.  In doing as many restorations as you seem to allude to, you should be sure that you are in capable hands.  Ask the dentist to show detailed before and after pictures of cases like yours he or she has completed before.  Ask about the nuances and intricacies specific to your case.  If you are going to go through all of this make sure you go through proper smiles design steps including photos with a 35mm SLR camera and wax-up diagnostic models. 

The implants should some first.  Once they are healed and integrated you can have temporaries placed to help design the smile and get proper tissue support.  Before you go to finals the temporaries should be in a condition or serve as a prototype for the finals.

Bonding over crowns and veneers is not a good idea. - strength and aesthetics are poor.  You can put a new crown