Influence of Finishing and Polishing Procedures on the Surface Characteristics and Flexural Strength of Monolithic Zirconia: An In Vitro Study

Aim:The aim of the present in vitro study was to evaluate the effect of the finishing and polishing system on surface roughness, topography, and flexural strength of monolithic zirconia.Materials and methods: A total of 20 samples were milled and sintered into bar-shaped specimens (16 × 4 × 1.6 mm) from a presintered yttriastabilized tetragonal zirconia polycrystal (Y-TZP block).They were divided into two groups containing 10 each.The control group consisted of glazed untreated zirconia.The experimental group consisted of specimens whose surfaces were roughened using a red diamond-coated bur for 20 seconds, and then they were polished using a Diacera intraoral polishing kit.The samples were evaluated quantitatively for surface roughness using a surface profilometer and qualitatively by scanning electron microscope (SEM), and the flexural strength of the two groups was tested using an Instron universal testing machine.The results were statistically analyzed using the Shapiro-Wilcoxon test and Mann-Whitney U test.Results: Scanning electron microscopic images showed evident differences in the topography of untreated, roughened, polished monolithic zirconia.The polished group had a lower average surface roughness value (Ra = 0.13 μm) when compared to untreated Zirconia.There was no statistically significant difference between the test and control group.The highest flexural strength was seen in the polished test group (max: 320.80 MPa).There was a statistically significant difference (p < 0.05) between the test and control group.Conclusion: Eve Diacera's zirconia polishing kit created a smoother and more uniform surface on monolithic zirconia.The flexural strength of roughened and polished monolithic zirconia was relatively higher than that of untreated zirconia.Under a SEM, there was an evident difference in the topography of untreated, roughened, and polished monolithic zirconia.Clinical significance: Finishing and polishing procedures mainly enhance esthetics, aid in reducing surface irregularities, and maximize biocompatibility by limiting bacterial adherence to the surface, among other advantages.Therefore, finishing and polishing are crucial for the longevity of the restorations.