Fluorapatite Glass-Ceramics: A New Sandblasting Approach for Zirconia Repair

Objectives: Zirconia repair could be a cost-effective option to a total replacement when zirconia prostheses fail. Sandblasting has been the routine method to establish a durable bond of repair materials to zirconia. This study investigated the effect of sandblasting with Fluorapatite glass-ceramics (FGC) on zirconia surface roughness, crystallinity, and repair for the first time
Methods: FGC ingots (IPS e.max ZirPress) were milled to powders with a particle size (D50) of 54 µm. Zirconia blocks (IPS e.max ZirCAD) were randomly divided into 3 groups (n=37) for different surface treatments (1-no treatment, 2-sandblasting with FGC powders and 3-sandblasting with tribiochemical silica-coated alumina CoJet sand). Surface roughness Ra (n=5) was measured using an optical profilometer. Surface topography and crystallinity were investigated by SEM and XRD. The remaining 30 specimens were divided into 3 groups according to the repair protocol used: a) MDP-Monobond Plus + Multilink Automix + Tetric EvoCeram Bulk Fill, b) MDP-Scotchbond Universal + Rely-X Ultimate + Filtek One Bulk Fill Posterior and c) Calibra Silane + SmartCem2 + Ceram-X Universal. Bonded specimens were subjected to 10,000 thermocycles between 5-55°C, dry stored (24-h) and shear bond strength (SBS) was tested at a speed of 1 mm/min. The results were statistically analyzed using one-way ANOVA and Bonferroni post-hoc test (P<0.05).
Results: Zirconia surface sandblasting with FGC powders showed a lower monoclinic phase and no significant difference in surface roughness compared to CoJet. The highest mean SBS was found in FGC-sandblasted zirconia with statistical difference (P<0.05) in groups a) and c) (16.48 and 11.32 MPa) compared to CoJet (13.05 and 7.97 MPa) respectively. However, the lowest SBS were found in control groups regardless the repair protocols.
Conclusions: Sandblasting zirconia with FGC powders effectively increased SBS of resin to zirconia by over 25% with lower monoclinic phase transformation compared to CoJet suggesting better clinical longevity.