Surface evaluation of milled chairside CAD/CAM materials based on manufacturing speed

The aim of the present study was to measure the surface roughness of monolithic chairside CAD/CAM zirconia materials to evaluate the influence of milling speed on the ability to create a clinically smooth surface. The null hypothesis was that there would be no significant difference in the surface roughness of different zirconia materials based on the speed of milling.

All test samples were milled from four different monolithic CAD/CAM zirconia blocks: Cerec Zirconia, Cerec Zirconia+, Cerec MTL Zirconia (all three Dentsply Sirona), and Katana Zirconia (Kuraray Noritake). Four different dry milling speeds - Super Fast/Good, Super Fast/Very Good, Fast, and Fine - were used to dry mill the specimens in a Cerec Primemill (Dentsply Sirona) milling unit. A 3D measuring laser microscope (OLS4100 LEXT; Olympus) was used to measure surface roughness.

Analysis of variance (ANOVA) was used to analyze the surface roughness data for each material and milling speed. There was a significant difference for milling speed (P 0.05) but not between the zirconia materials (P > 0.05).

Based on the limitations of the present study, the milling speed was found to influence the surface roughness of dry milled and sintered zirconia, with slower speeds resulting in smoother surfaces. The largest improvement in surface roughness occurred between the Super Fast and Fast milling speeds, with a smaller incremental improvement in surface roughness with Fine milling in the Primemill. All recorded surface roughness values were within the expected range of values to be able to efficiently hand polish a clinically acceptable surface finish.