Surface Evaluation of Chairside CAD/CAM Zirconia after Contouring and Polishing

Objectives: This in-vitro study measured the differences in surface smoothness of hand polished chairside CAD/CAM zirconia materials using different contouring/polishing techniques.
Methods: Groups of 12 samples for each combination of material and contouring/polishing technique (N=144) had a cuspal coverage onlay designed on CEREC Omnicam SW 4.5.2 and milled on an MCX milling unit (Dentsply Sirona). All samples were sintered using Speedfire oven (Dentsply Sirona) before contouring/polishing. The materials included Cerec Zirconia 3 mol% (Denstply Sirona), 3M Chairside Zirconia 4 mol% (3M ESPE) and Katana Zirconia 5 mol% (Kuraray Noritake). One calibrated operator polished groups of each material with 3 polishing sytems: spiral polishers=SP (Dialite ZR FeatherLite/Brasseler), wheel polishers=WP (Luster for Zirconia/Meisinger), and brush-paste=BP (Diashine/VH Technologies). 3D surface roughness (Sa) was assessed using a confocal laser microscope (Lext OLS4000/Olympus).
Results: Analysis of variance showed a statistical significance in the means of Sa (p<0.05). Tuckey test revealed that the polished surface of all materials was significantly smoother than the baseline milled surface (p<0.05). The baseline surface of 3M Zirconia and Cerec Zirconia were significantly smoother than Katana Zirconia. There was no significant difference in the surface smoothness for any of the polished surfaces.
Conclusions: For all materials, the Sa values of the polished surfaces were significantly smoother than baseline values. 3M Zirconia and Cerec Zirconia had significantly smoother baseline milled surfaces compared to Katana Zirconia. All three types of zirconia polishers created equally smooth surfaces for all materials tested. This study was funded by a grant from the University of Michigan Rackham School of Graduate Studies.