Comparison of surface roughness parameters R_a/S_a and R_z/S_z with different measuring devices

Objectives: The aim of this in-vitro study was to investigate the influence of the measuring devices (mechanical and optical) on the surface values Ra/Sa and Rz/Sz of different materials and machined surfaces. Material and methods: Mechanical (contact profilometry (CP): Perthometer S6P, Perthen Mahr, G) and optical (scanning electron microscope (SEM): Phenom, FEI, NL; confocal 3D laser scanning microscope (CLSM): VK-100, Keyence, J) measuring devices were used to determine the surface roughness Ra/Sa and Rz/Sz. Glass-ceramic (Empress, Ivoclar-Vivadent, FL), zirconia (Cercon HT, Dentsply, D), composite (Grandio, Voco, D), denture base material (Palapress, Kulzer, D) and titanium (grade 4) were investigated (n = 10 measurements) after surface finishing: sandblasting (Al2O3; 250 mu m), diamond treatment (80 mu m; wet), sandblasting (Al2O3; 50 mu m), and polishing (grit of 4000; wet; Tegramin-25, Struers, D). Statistics: Shapiro-Wilk, ANOVA, Bonferroni post-hoc tests (alpha = 0.05). Results: Surface characteristics Ra/Sa and Rz/Sz, which were detected with mechanical and optical measuring devices on different materials and surface finishing, showed significant (p <= 0.001, ANOVA) differences. Significant (p <= 0.045, Bonferroni) differences between CP, SEM and CLSM (line; area) were found, mainly for Ra/ Sa. Discussion: The surface roughness on different dental materials and differently machined surfaces were influenced by the individual mechanical and optical measuring devices. Optical methods measure a significantly higher roughness value for all materials and surface finishes.