ABSTRACT
This study investigated the two-body wear resistance of a first generation 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), a second generation 3Y-TZP, a third generation 4 mol% yttria partially stabilized zirconia (4Y-PSZ), a 5 mol% yttria partially stabilized zirconia (5Y-PSZ), and a type III gold alloy (Aurocast 8), performed using opposing antagonistic cusps made out of the same material. Eight cylindrical specimens were prepared for each material (n = 8) for a total of forty specimens (N = 40). Conical cusps were fabricated for each material. Each cylinder−cusp pair was arranged inside a two-axis chewing simulator over up to 360,000 loading cycles. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm3). The antagonist wear (mm) was recorded before and after the wear test to evaluate the linear difference. Statistical analysis was performed using one-way analysis of variance (ANOVA); multiple comparisons were performed according to Tukey's method. No statistically significant differences (p > 0.05) among the first generation 3Y-TZP, second generation 3Y-TZP, and 4Y-PSZ wear were found. 5Y-PSZ showed statistically significant higher wear compared to other the zirconias. Aurocast 8 displayed the highest values in terms of vertical wear, antagonist cusp wear, and volumetric loss. Although still not statistically comparable, the wear behavior of the latest 5Y-PSZ was the closest to the widely recognized gold standard represented by the type III gold alloy.
ABSTRACT
OBJECTIVE: To investigate the shear bond strength (SBS) of a glass ionomer (GI) cement, an 10-methacryloyloxy-decyl dihydrogen phosphate (MDP)-based adhesive resin cement (MDP-based AC), an MDP-based self-adhesive resin cement (MDP-based SAC), an MDP-free self-adhesive resin cement (MDP-free SAC), and a resin-modified GI (RMGI) cement to a 3 mol% yttria-stabilized (3Y-TZP) and a 5 mol% yttria partially stabilized zirconia (5Y-PSZ). MATERIALS AND METHODS: Fifty blocks were produced using 3Y-TZP and 5Y-PSZ, assigned to subgroups based on the five cements investigated (n = 10) and luted to cylindrical specimens of the same substrate. Each specimen was loaded in a SBS apparatus to failure. Mean SBS (MPa) values and standard deviations were calculated. Data were analyzed using a two-way analysis of variance and Tukey tests (α = .05). Failed specimens were subjected to fractographic analysis. RESULTS: MDP-based AC and MDP-based SAC cements displayed the highest SBS values with both the substrates; GI cement showed the lowest. RMGI and MDP-free SAC cements performed better with 3Y-TZP than with 5Y-PSZ. Fractographic analysis revealed only adhesive and mixed failures. CONCLUSIONS: MDP-based AC and MDP-based SAC cements are suitable for both 3Y-TZP and 5Y-PSZ. MDP-free SAC and RMGI cements are adequate choices for 3Y-TZP, but seem less effective with 5Y-PSZ. CLINICAL SIGNIFICANCE: MDP-based SACs appear to be as reliable as MDP-based ACs for both 3Y-TZP and 5Y-PSZ cementation. Specifically, for 5Y-PSZ cementation, resin-based MDP-free SACs do not seem to guarantee predictable results in terms of SBS.
