Traditional veneers (metal-supported or some zirconium veneers) are bonded to the tooth surface with conventional cements (zinc phosphate or glass ionomer). Retention here is entirely mechanical; that is, the tooth’s cutting geometry (parallelism, length) and the frictional force created by the drying of the adhesive hold the veneer in place (cement retention). Adhesive bonding, on the other hand, is used especially in all-ceramic veneers such as E-max or laminates. In this method, the inner surface of the porcelain is roughened with hydrofluoric acid, silanized, and chemically bonded to the tooth with special resin adhesives. This bond is a molecular-level welding process, and the tooth and porcelain become a single piece. The retention strength of adhesive bonding is many times higher than that of mechanical cements; therefore, the risk of restorations bonded with adhesive systems falling off is almost negligible.
