Wear behavior of different ceramics against zirconia substrates

This study aimed to evaluate the wear behavior of different ceramic materials opposing different zirconia ceramics with distinct surface roughness.

Method:

Sphere-shaped samples (diameter 5 mm) were fabricated out of two different leucite-glass based veneering ceramics (VM9, Vintage ZR), lithium-disilicate ceramic (Emax Press) and human enamel. The samples were embedded as antagonists in a mastication simulator and tested against disks of three zirconia materials (Zenostar, Cercon, NanoZr) with different surface roughness (R_a=0.01, R_a= 0.1 and R_a=1). An enamel-enamel wear evaluation was used as reference. Each group was loaded in a mastication simulator for 1.2x10⁵ cycles under a load of 98 N with simultaneous thermocycling (5/55°C). The samples were scanned using a laser scanner and volumetric loss was quantified using analysis software. Further characterization included scanning electron microscopy (SEM) to evaluate the wear performance of the samples and antagonists as well as Raman spectroscopy to determine the crystalline property of the zirconia specimens.

Result:

The lowest volumetric loss of zirconia specimens (enamel reference: 0.056 ± 0.457 mm³) resulted 0.001 ± 0.001 mm³ (p<0.0001) when NanoZr (R_a=0.01) was opposed to enamel. The highest wear amounted 0.369 ± 0.148 mm³ (p<0.0001) with Cercon (R_a=1) versus Vintage ZR ceramic. For the antagonists, enamel opposed to Zenostar (R_a=0.01) showed the lowest volume loss of 0.034 ± 0.019 mm³ (p<0.0001) (enamel reference: 0.63 ± 0.46 mm³) and VM9 ceramic against Zenostar (R_a=1) demonstrated the highest wear of 2.671 ± 0.352 mm³ (p<0.0001). SEM showed no differences in the wear patterns among different samples. Raman spectroscopy revealed that thermomechanical fatigue did not influence the levels of tetragonal and monoclinic phase of different zirconia samples.

Conclusion:

The wear behavior of monolithic zirconia is influenced by the type of antagonist material. Higher surface roughness of substrate zirconia samples correlates positively with increased wear of antagonist materials.