Zirconia bonding: ZirClean and Z-Prime Plus enhance the reliability of restoration adhesion

At the Greater New York Dental Meeting, Rolando Nunez, DDS, MS (BISCO), presented a lecture dedicated to bonding zirconia restorations and the role of ZirClean and Z-Prime Plus in achieving stable adhesion.

Executive summary

In his presentation, Dr. Nunez emphasized the clinical importance of consistent surface preparation for zirconia restorations: removing contaminants, creating optimal micro-roughness, and applying a chemically active primer to ensure strong adhesion to zirconia restorations.

Key points of the presentation

• Speaker: Rolando Nunez, DDS, MSc (BISCO).
• Topic: Zirconia bonding – clinical protocols and products.
• Products discussed: ZirClean (surface cleaner) and Z-Prime Plus (primer containing functional monomers for chemical bonding to zirconia).
• Goal: increasing the reliability and longevity of the adhesive bond between zirconia restorations and abutment structures.

Clinical significance and rationale.

The problem

Zirconia is characterized by low surface reactivity and the absence of a glassy phase, which limits direct chemical bonding with traditional adhesive systems. Clinically, this results in reduced initial bond strength and potential loss of restoration retention under masticatory load.

Adhesion strategy

Dr. Nunez described a combined approach: mechanical increase of the contact area (micro-roughness) and chemical activation of the surface using functional monomers (MDP and similar), which provides the most predictable results.

Surface preparation and product application protocol

Step 1 — Mechanical treatment

Prior to chemical treatment, controlled air abrasion of the zirconia surface (using Al₂O₃, fine-grit abrasive) is recommended to create micro-roughness and enhance mechanical adhesion. Alternatively, light micromechanical processing at the laboratory stage is possible, followed by verification of the restoration’s anatomical integrity.

Step 2 — Cleaning: Application of ZirClean

ZirClean is used to remove organic and inorganic contaminants (plaster residues, colloidal phases, modeling residues, and fingerprints) that may prevent the primer from contacting the surface. The presentation emphasized that cleaning before primer application improves result reproducibility.

• Apply and allow to set briefly according to the manufacturer’s instructions.
• Thoroughly rinse and dry the surface to remove the solvent before the next step.

Step 3 — Chemical activation: Application of Z-Prime Plus

Z-Prime Plus (BISCO’s primer containing functional monomers, including MDP) acts as a chemical intermediary, providing a strong bond between the zirconia oxide surface and the polymer cement matrix. Dr. Nunez recommended strictly adhering to the manufacturer’s specified application time and drying technique to form a stable adhesive layer.

• Apply a thin layer of Z-Prime Plus to the cleaned and prepared surface.
• Allow it to set for the recommended time and gently air dry to remove the solvent and orient the monomers.

Step 4 — Cementation

Following primer application, a resin cement should be applied. For maximum long-term stability, the use of cements compatible with MDP-containing primers (e.g., adhesive or self-etch resin cements recommended by the manufacturer) is indicated. Control of the cement layer and polymerization according to clinical requirements is mandatory.

Results and clinical observations

The presentation included clinical observations and laboratory data confirming that the sequence: air abrasion → cleaning with ZirClean → priming with Z-Prime Plus → application of a suitable resin cement provides high initial bond strength and increased resistance to fatigue failure compared to non-facilitated protocols.

Expert commentary and practice recommendations

• Always consider the final processing of the restoration in the laboratory and the impact of potential contaminants on adhesion.
• The “clean → prime” sequence is crucial: applying primer to a contaminated surface reduces the effectiveness of the functional monomers.
• The use of MDP-containing systems remains the “gold standard” for chemical bonding to oxide ceramics, including zirconia.
• The presentation emphasized the importance of following the manufacturer’s instructions for each product (dwelling time, drying method, cement compatibility).

Findings

The presentation by Rolando Nunez confirmed that integrating specialized products—the ZirClean cleaner and Z-Prime primer—into the clinical protocol for zirconia bonding enhances the predictability and durability of the adhesive interface. The combination of mechanical preparation and chemical surface activation remains crucial for successful cementation of zirconia restorations.