Zirconia surface treatment for successful bonding.

Q.

I often use zirconia such as LAVA or Cercon for crown restoration. However, they tend to fall off more easily compared to other materials. What should I do for better adhesion?

A.

Due to its high strength and biocompatibility, the use of zirconia is recently on the rise, but there are difficulties in bonding compared to other conventional ceramic materials. Since it doesn't contain glass, it cannot be etched by hydrofluoric acid and tribochemical silica coating is not effective.1,2 Therefore, unlike conventional materials, the adhesion with luting cement is weak and the restoration easily falls off.1 Therefore, the tooth surface should be treated with conventional methods, but the inner zirconia surface needs special treatment.1,2,3,4

Currently, the most effective method for zirconia bonding is to apply sandblasting, rinse ultrasonically, and then coat zirconia primer (Z-PRIME Plus, Bisco Inc., Schaumburg, IL, USA)1,2 or universial adhesive (Scotchbond Universal Adhesive, 3M ESPE, St. Paul, MN, USA; All-Bond Universial, Bisco Inc.), which includes fuctional monomers such as 10-methacryloyloxydecyldihydrogen phosphate (MDP), etc.3,4 Unlike conventional restorative materials, when used with zirconia, conventional multistep cements do not have significantly higher bonding strength.2 Therefore, self-adhesive resin cement (SmartCem2, Dentsply, York, PA, USA; Rely X U200, 3M ESPE; BisCem, Bisco Inc.; PermaCem 2.0, DMG, Hamburg, Germany; Multilink Speed, Ivoclar Vivadent, Schaan, Liechtenstein) may be conveniently used for cementation as saving time and reducing errors of multistep processing. The manufacturers do not recommend the use of additional surface treatment on restorations as the self-adhesive resin cement contains functional monomers, but the use of aforementioned primers significantly increase the bond strength.1,2 Zirconia adhesion needs improvement through further research and development.