What would cause a semi-large white spot in a permanent veneer?

Hey there,It's hard to know for sure, but it is likely one of two things.  This could be artifact resulting from the shading of the veneer, which would be a lab error.  Or this could be some try-in paste that was left on the prep, prior to cementation or possibly the type of cement that was used.  Good luck and I hope this helps. Follow me if you have more questions.Sarah Thompson, DMDSt. Louis, MO area (O'Fallon, IL)Real Self 100

Ideally, a porcelain veneer is as thin as possible, resulting in conservative treatment.  There is a fine line, too thin may break, or too thin and color can be an issue.Sometimes tooth structure is very dark, so a veneer can be used to lighten it up (but the tooth darkens the veneer a little).  Sometimes the tooth structure is very light and can shine through as a whiter spot.When veneers are created, the lab will create space or room for the eventual cement that bonds the veneer to the tooth.  Ideally this space is uniform so the cement is not thicker in some areas and thinner is others.  If the veneer did not fit at try in, sometimes a dentist will polish the tooth to get a better fit.  This can result in an area where the thicker cement is visible.  It may not be an issue over time, as the tooth will re-hydrate and the restoration will blend better.  Otherwise, it likely means to replace the veneer.

It's difficult to tell without a photo, and without doing an exam on you.  However there are a few possibilities.  The veneers are made out of porcelain, and they should not change on the exterior surface.  It may be possible that there is excess cement on the outer portion of the veneer.  It can also be that there was an area of translucency on the veneer, and with the cement underneath, it may be showing through.  It is best to go back to your dentist and see what the cause is.  If he is unable to resolve the issue, and it continues to bother you, ask him/her to replace the veneer.