Three-body Wear of CAD/CAM Restorative Materials against Zirconia

Objectives: To evaluate three-body wear of different CAD/CAM and direct restorative materials opposed to zirconia (ZrO₂) antagonist wheels in an ACTA wear machine.

Methods: Specimens (n=10) suitable for the compartments of the ACTA wear machine were prepared from bovine enamel, amalgam (Silber70-Solo, DMG), six CAD-CAM based composite and hybrid-ceramic blocs (Grandio blocs, VOCO/ Tetric CAD, Ivoclar Vivadent/ Lava Ultimate, 3M OralCare/ Brilliant Crios, Coltene/ Cerasmart, GC/ VITA Enamic, VITA), one lithium disilicate ceramic CAD-CAM material (IPS e.max CAD, Ivoclar Vivadent) and three direct composite resins (Clearfil majesty posterior, Kuraray/ Grandio SO, VOCO/ Filtek Supreme XTE, 3M OralCare). After storage (28d, aqua dest., 37°C) 200,000 wear cycles were performed against an antagonist wheel (Y-TZP, Prettau, Zirkonzahn, d=20mm, h=6mm, F=15N, f=1Hz, 15% slip) in millet seed suspension as third medium in the ACTA wear machine. Mean wear depth and roughness (Ra) were analysed in a 3D optical non-contact profilometer (CT100, CyberTechnologies) equipped with a confocal white-light sensor CHR-600 (CyberTechnologies (z-res.=0.02µm)). Vickers hardness (HV) was measured using a Vickers indentation tester (15s indentation time, HV2, Zwick Roell). Statistical analysis was performed using non-parametric statistics (Kruskal-Wallis and Mann-Whitney-U test).

Results: Bovine enamel showed the significantly highest wear depth opposing the ZrO₂ antagonist. The ZrO₂ wheels had no signs of abrasion. Similar wear resistance was tested for direct and indirect resin based materials with analogous filler configurations. The lithium disilicate ceramic IPS e.max CAD showed the significantly highest Vickers hardness, which led to the best ACTA wear-resistance. No correlation between mean wear depth and roughness or Vickers hardness could be found.

Conclusions: Among the materials tested, composites performed amalgam-like, while the lithium disilicate ceramic showed the highest and bovine enamel the lowest three-body wear-resistance. The high Vickers Hardness of the lithium disilicate ceramic and the prismatic structure of enamel may influence the differing wear behavior.