Can you replace only a few veneers?

As long as you have an excellent cosmetic dentist, they should be pretty proficient at matching shade.  I do this type of thing all the time, when patients come to me, having had veneers done by another dentist.  If your new dentist has any concerns about matching shade, you should have your records sent from your previous dentist.  Veneers are what I do, so "Follow" me if you have more questions about them.Sarah Thompson, DMD

In general it is not a good idea to go in and try to replace three veneers if eight have been done and you want changes in length or shape.  You may accomplish one thing, but it is more likely that the results will be that there are then more things you don't like about them after the adjustment or replacement.  Problems like the color not matching, no continuity in the shape (smile design), a bad bite (uneven occlusion), etc.Most cosmetic dentists and plastic surgeons offer payment plans through CareCredit, which can oftentimes be set up so that you won't have any interest on the cost of your dentistry for the first year.

The best thing to do would be to find out what material was used for the veneers and at the same time the shade. Your previous dentist may be able to find it out and the lab that was used should probably have it in their records. Otherwise your new dentist should be able to match the new veneers to the ones which you are keeping- it is a more difficult task to go this route as even the slightest amount of difference can be noticed when you are dealing with the front teeth.

The short answer is yes.  The challenge is matching shades but a good cosmetic dentist should be able to accomplish that for you.  It would be helpful to know if possible what material and shade was used originally.  Your original dentist should have that information in your record.You mentioned no dentist would shorten your existing veneers due to liability.  If your only issue is length I certainly would try again to find someone who would adjust the length before redoing them.  If adequate length exists to shorten the porcelain it is doable.

Altering or contouring as you initially requested CAN be done, but comes with risks.  If the veneer is only 0.5 mm long and you want it shortened by 1.0 mm, then the entire veneer needs to be replaced.  Often the last 0.5 mm of a veneer is more translucent and any shortening will remove this characteristic.  This leads to a "not very pretty" outcome.Replacing a few is a better option, but has its own challenges including shade match, metamerism, durability among others.  The answer is "yes" but it isn't as easy as one would think.