The effect of surface treatment and glass-ceramic coating on the wear behavior of different types of zirconia and their antagonists.

Objectives: In-vitro study to investigate the influence of different pre-treatments and surface coatings on the wear of different zirconia and their antagonists.

Method and materials: Zirconia specimens (3-, 4- and 5-mol yttria tetragonal zirconia; n=160/material) were subjected to pre-treatment (sandblasting 50 μm Al2O3 1 bar; 120 μm Al2O3 3 bar; polishing) and surface coating (spray glazing, micro-layering, layering, veneering). References comprised no pre-treatment or coating. Wear tests were performed (50 N, 120,000 cycles). Wear (mean, maximum, antagonist) and arithmetic mean roughness Ra and average roughness depth Rz were determined.

Statistics: ANOVA, Bonferroni, Pearson correlation (α=0.05).

Results: Ra/Rz showed significant (p < .001) differences (Ra: 0.01 ± 0.01 μm to 0.71 ± 0.06 μm, Rz: 0.31 ± 0.09 μm to 4.33 ± 0.44 μm). Two groups could be distinguished by mean and maximum wear with significant (p < .001) differences: I.) glaze sprayed and without coating (mean wear: 9.4 ± 2.6 μm to 57 ± 21.3 μm, max. wear: 24.1 ± 6.9 μm to 125.4 ± 18.2 μm) and II.) All coating procedures (mean wear: 129.2 ± 22.8 μm to 236.5 ± 62.0 μm, max. wear: 188.7 ± 21.4 μm to 444.2 ± 110.6 μm). Antagonist wear (9.2 ± 4.5% to 29.7 ± 5.0%) showed a significant (p < .001) correlation to surface coating, mean and maximum wear, Ra and Rz. Mean wear significantly (p < .001) correlated with surface coating, maximum wear, and antagonist wear.

Conclusion: Under clinical conditions, layering or veneering can lead to increased wear of the restoration, but in return reduce the abrasion of antagonists. Excessively rough surface treatments should be avoided, as they might increase antagonist wear.