Effect of air-particle-abrasion on cyclic and flexural strength of zirconia

Objectives: Although air-particle-abrasion delivers advantages for improved adhesive strength of resin cements to yttria-stabilized tetragonal-zirconia-polycrystalline (zirconia), it is not widely studied whether this process impairs the mechanical properties of such ceramics. The objectives of this study were to evaluate the effect of different air-particle-abrasion protocols on the cyclic fatigue and biaxial flexural strength of an experimental and commercial zirconia. Methods: Disc shaped sintered zirconia specimens (diameter:15 mm, thickness:1.2 mm) (N=64 / n=8 per group) were obtained from the manufacturers (experimental and Vita YZ, Vita). Three air-particle-abrasion protocols (distance: 10 mm; pressure: 2.9 bars, duration: 20 s), namely 1) 50 µm Al2O3 particles, 2) Laboratory silica coating with 110 µm alumina particles coated with silica (Rocatec Pre and Plus, 3M ESPE) and 3) Chairside silica coating with 30 µm alumina particles coated with silica (CoJet, 3M ESPE) were employed on the cementation surface of the specimens. Control group received no surface treatment. All specimens were tested for biaxial flexural strength (ISO 6872) after being subjected to mechanical cycling (20.000 cycles under 50N load, immersion in distilled water at 37°C) in a universal testing machine (1 mm/min). Results: Both zirconia type (p=0.001) and the air-particle-abrasion protocols (p=0.001) showed significant affect on the results (2-way ANOVA, Tukey's test, á=0.05). Control group of experimental zirconia (736±68) showed significantly higher results (MPa) than that of Vita YZ (453±36) (p<0.05). Air-abrasion with 50 µm Al2O3 (628±124, 440±90) showed significantly lower results than with Rocatec (779±90, 562±104) for both experimental and Vita YZ, respectively. Air-abrasion with CoJet in both zirconia (738±75 and 613±64 MPa for experimental and Vita YZ, respectively) did not significantly differ from those of Rocatec treatment (p>0.05). Conclusion: Both laboratory and chairside air-abrasion protocols could be suggested to alumina treatment for treatment of cementation surfaces of zirconia.