SPONSORED EDITORIAL
Bonding to Zirconia
Zirconia Cannot Be Bonded?
Ever since zirconia crowns were commercialized in the early 2000s, researchers and clinicians have tried various methods to bond zirconia, such as hydrofluoric acid-etching followed by silanization, or silica-coating followed by silanization. Hydrofluoric acid-etching followed by silanization has been proved to be a predictable procedure for bonding glass-ceramics. However, it is not effective for zirconia bonding. Silica-coating is effective for the surface treatment of softer materials, such as metal. However, it is not effective for the treatment of zirconia, which has a much harder surface. Therefore, many clinicians and researchers experienced failure bonding to zirconia in the early 2000s, and they thus believed that zirconia could not be bonded.
Zirconia Demands Adhesively Bonding
Research studies showed that the retentive zirconia restorations, such as full-coverage zirconia crowns, could be successfully luted (without the need of adhesively bonding) with RMGI or self-adhesive resin cements. However, the use of zirconia in conservative aesthetic dentistry in combination with short, non-retentive preparation designs commonly seen in today’s complex restorative cases demands that chemistry be created to allow development of adhesive primers, specific to glass-free polycrystalline ceramic materials (zirconia). This chemistry enhances the adhesion between hydrophobic resin composites/cements and indirect polycrystalline ceramic substrates. BISCO’s goal was to create a cohesive interface between the zirconia and resin cement, improve initial bond strengths capable of resisting hydrolytic degradation, and allow for the use of stronger and more durable resin cements.
The Optimal Procedure for Zirconia Bonding
Numerous research studies showed the most reliable method to bond zirconia is sandblasting followed by priming with a phosphate monomer. Specifically, the optimal clinical procedure for zirconia bonding includes four steps: sandblast zirconia internal surface with alumina sand; apply MDP-based zirconia primer on zirconia; apply dental adhesive on tooth; and seat zirconia restoration with a resin cement.
Zirconia Is Special—Saliva Contamination
Unlike other indirect restorations, zirconia would react with phosphate-containing compounds, which include saliva and phosphoric acid etchant, resulting in an adverse effect on the zirconia bond. The adverse effect cannot be eliminated by simply cleaning with water or organic solvents. Only a strong alkaline solution (such as potassium hydroxide solution) can clean the contaminant and eliminate the adverse effect. BISCO’s ZirClean, which is based on potassium hydroxide, has thus been developed.
Bonding to zirconia doesn’t have to be difficult. Paired together, ZirClean and Z-PRIME Plus can enhance zirconia bond strengths by cleaning and priming zirconia, ceramic, and metal restoration surfaces.
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