Comparative evaluation of 2-step and 3-step polishing systems on the surface roughness and flexural strength of lithium disilicate: An in vitro study

Aim: The aim of this in vitro study was to investigate the effects of 2-step and 3-step polishing systems on the surface roughness and biaxial flexural strength of lithium disilicate ceramics after grinding. Settings and Design: Thirty-two 14 x 1.25 mm lithium disilicate (IPS e.max CAD) discs were divided into four groups ( n = 8): control (unmodified), ground-unpolished, ground-3-step polished (Shofu Zil Master), and ground-2-step polished (Toboom). A profilometer was used to quantify the surface roughness (Ra, µm), and ISO 6872 was followed to calculate the biaxial flexural strength (MPa). Materials and Methods: A profilometer was used to quantify the surface roughness (Ra, µm), and ISO 6872 was followed to calculate the biaxial flexural strength (MPa) of all the samples. Statistical Analysis Used: The data were analyzed through the IBM SPSS Statistics software package (Version 25.0). One-way Analysis of Variance (ANOVA) was used to check variations among the groups followed by the Tukey’s post hoc test (α=.05). Results: There were significant differences between the groups in both flexural strength and surface roughness ( P <.001). As compared to the control, the 3-step system (0.43 ± 0.21 µm) provided smoother surfaces than the 2-step system (0.78 ± 0.34 µm). The control group (1696.8 ± 486.9 MPa) and the 3-step group (1500.0 ± 306.2 MPa) had the highest flexural strength, whereas the 2-step group (951.3 ± 121.2 MPa) had the lowest values. Conclusions: The flexural strength and surface roughness of ground lithium disilicate were enhanced by both polishing systems; however, the 3-step system performed better and produced outcomes that were on par with unaltered ceramics.