Q. I have 6 veneers on my front top teeth. I had them placed over 20 years ago and have never had any problems. Last year one fell of and was successfully replaced. About a month later one of my large front ones fell off and has been replaced 3 times. Two others came off after that and they seem to have been successfully replaced. My question is can the porcelain from the one which keeps falling off be contaminated in some way or is it more likely to be either the bonding or the process which is at fault?,