The effect of nonthermal argon plasma surface treatment on the fracture resistance of monolithic zirconia restorations containing tetragonal and cubic grains

Purpose: The aim of this study was to investigate the effect of nonthermal argon plasma (NP) surface treatment on the fracture resistance of mono-lithic zirconia restorations with different microstructures. Methods: Twenty restorations were prepared from each of two tetragonal and two cubic zirconia materials (80 restorations in total). The restora-tions were then divided into two subgroups (n = 10) for each material according to the surface treatment applied: air abrasion or NP. The surface topography of the treated groups was examined using a scanning electron microscope. All restorations were fixed to metal dies with resin cement, subjected to thermal cycling, and then underwent fracture resistance test-ing with a universal testing device. Two-way ANOVA and Bonferroni tests were used for statistical analysis of the data (alpha = 0.05). Results: The type of surface treatment and the type of zirconia material were shown to significantly affect the fracture resistance of the restorations. The air-abraded groups showed significantly higher fracture resistance (N) than the NP groups (P < 0.001). Conclusion: The results of this study suggest that air abrasion surface treatment has a more favorable effect on the fracture resistance of tetrago-nal and cubic zirconia restorations than NP surface treatment.