Effect of different surface treatments on the bonding potential and physical and mechanical properties of ultratranslucent zirconia

Statement of problem. Studies to determine a suitable surface treatment that improves bonding without compromising the strength or translucency of ultratranslucent zirconia are scarce. Purpose. The purpose of this in vitro study was to evaluate the effect of different surface treatments on translucency, surface topography, phase transformation, biaxial flexural strength, bond strength, and durability. Material and methods. A total of 169 ultratranslucent zirconia disks were randomly divided into 4 groups according to the surface treatment applied: airborne-particle abrasion (APA) (n=46), tribochemical silica airborne-particle abrasion (TS) (n=46), nonthermal oxygen plasma (NTP) (n=46), and no treatment, control (C) (n=31). The translucency parameter (Delta TP00) was evaluated with a spectrophotometer (n=15), phase transformation was assessed with an X-ray diffractometer (n=5), surface topography was evaluated with a scanning electron microscope (SEM) (n=3), and biaxial flexural strength (BFS) was tested with a universal testing machine (n=15). For the microshear bond strength (mu SBS) test, 40 composite resin specimens were attached to 8 disks and tested with a universal testing machine; 20 specimens were tested after 24 hours, and 20 specimens after hydrothermal aging in a thermocycler (TC). The data were analyzed with ANOVA followed by the Tukey post hoc test (alpha=.05). Weibull analysis was performed for the flexural strength and mu SBS results. Results. Significant Delta TP00 differences were found among all groups and were highest for the APA group (7.33) and lowest for the NTP group (4.79). The NTP group had a significantly higher monoclinic weight fraction value (4.54%) than other groups. The NTP group had significantly higher BFS (581.31) than other groups, while the APA group showed significantly lower values than other groups (340.43). The APA group had significantly higher mu SBS values after 24 hours (13.51 MPa) and after TC (13.68 MPa) than the other groups (P<.05). Conclusions. Although APA and TS are effective techniques for improving resin-zirconia bonding, they result in significantly higher deterioration of translucency and strength. NTP significantly improved the BFS of zirconia; however, it showed lower bond strength values than other methods.