Influence of Finishing Procedures on Surface Roughness and Biaxial Flexural Strength of High-translucent 4Y-PSZ, 5Y-PSZ, and 6Y-PSZ Monolithic Zirconia

Objective: This study aims to investigate the effects of glazing, polishing and polishing with a polishing paste of newly developed highly translucent materials on the flexural strength of these materials and aims to illuminate where there is not much study yet on the finishing procedures to be done. Methods: Three different high translucency Y-PSZ (Yittria partially stabilized zirconia): KST (Katana STML), KUT (Katana UTML), NCQ (Nacera Pearl Q3 Multi-Shade) and one translucent 3Y-TZP (3-yttria stabilized tetragonal zirconia polycrystalline): NCMS (Nacera Pearl Multi-Shade) zirconia system were used. A total of 120 specimens were prepared in the form of discs with a diameter of 14 mm and dimensions of 1.2 +/- 0.2 mm. Three experimental groups (n = 30) were formed from each type of material, using three finishing protocols: Diamond Polishing system (DP); Diamond Polishing system followed by Polishing Paste (PP); Glaze Application (GP). Surface Roughness (Ra) was measured by using a contact profilometer, and a biaxial flexural strength test was applied to determine their flexural strength. The obtained data were analyzed using the Weibull distribution. All results were evaluated statistically. Results: For Ra values, there was a statistical difference between all the procedures applied in the KST material as in the NCQ material. However, there was no statistical difference between GP and PP procedures in Ra values in the NCMS material and between DP and PP procedures in the KUT material. The characteristic strengths of DP applied to NCMS and NCQ material, PP applied to KST, and KUT material had the highest value. The highest m values for DP were determined in KST, NCMS, NCQ materials, while in KUT material, PP was determined in the finishing procedure. Conclusion: Finishing procedures have significant effects on surface roughness and flexural strength values for translucent zirconia materials. The lowest Ra value and the highest flexural strength were found in the DP group of NCMS. In KST and KUT materials, the highest flexural strength results were found in the PP procedure while NCQ was not affected by finishing procedures.