Agree with previous answer. The bonding would be a very short term fix. The veneers would need to be redone to lengthen them.
Can Porcelain Veneers Be Bonded Outside to Adjust the Length and Also Can It Grind to Shorten?
Doctor Answers 2
Grinding or Lengthening Porcelain Veneers
When Porcelain Veneers are done by a qualified cosmetic dentist, all the issues of length should be worked out in the temporary phase. The final Veneers should look and function perfectly. Any bonding done after the fact to lengthen them will not stay and will not look great. Also, any gringing down of the Veneers can potentially weaken or fracture them.