A few of my colleagues discussed how to cement porcelain veneers. This is the protocol that I always follow:
If the veneers are etched by the dental laboratory, and usually, they are, then this is what I do:
After receiving the veneers from the dental laboratory, I inspect the inner surface. Properly etched veneers should have a dull/ matte finish and no shiny areas.
If the veneers have shiny areas, means they were not properly etched then I briefly sandblast and re-etch with 9.5% HF for 90 seconds. In the case of IPS e.max, I use 5% HF for 20 sec.
If the veneers appear well etched, then:
I clean the veneers with phosphoric acid for 10 sec, wash, and dry. The basic idea is to ensure a clean, fresh, high-energy surface before applying silane, as it may be possible the veneers were contaminated from normal handling and exposure at some point between the laboratory and the time of placement.
Before the veneers are tried in, apply one to two coats of silane and warm-air dry for 60 seconds. The surface should not look shiny.
Try in veneers to access fit and esthetics. Once approved, place the veneers back in the ultrasonic to remove any surface contaminants. Silane does not need to be re-applied again.
Then the cleaned veneers should be dried thoroughly and brushed with a thin coat of HEMA-free bonding resin. (porcelain bonding agent) , not cured and then I apply the cement.