To do a root canal on front teeth, the access is made through the back of the teeth. So, the veneer in front of the tooth will be untouched. Once the root canal treatment is completed, the hole in the back surface of the tooth can be patched up with white composite filling.
However, it should be noted that a crown is the recommended treatment after root canal treatment since the tooth will become weak and brittle following a root canal. To avoid fracture of the tooth, a full-coverage crown is preferred to a veneer. Best, Dr. Elizabeth Jahanian