Effects of various extra-oral surface treatments on stainability of translucent monolithic zirconia

Monolithic zirconia restorations are one-piece and have superior mechanical properties. While monolithic zirconia finds less use in the anterior region due to its optical properties, desired aesthetics can be achieved in the anterior region thanks to monolithic zirconia with high translucency produced in recent years. In the treatment of prosthetic teeth, it is of great importance that the materials used especially in the anterior region have mechanical properties as well as aesthetic properties and thus ensuring color stability. In this thesis study; glazing, polishing and polishing+paste (n=117) was applied on samples produced from CAD/CAM (computer aided design/computer aided manufacturing) zirconia blocks (Dental Direct; DD cubeX²®, DD cube ONE®, DD Bio ZX2). The roughness of the sample surfaces with different surface treatments (n=108) was measured with an optical profilometer, and the topographic properties of one sample from each group (n=9) were measured with a scanning electron microscope, then all samples were subjected to thermal cycling using coffee with 5000 cycles, and the coloration before and after the thermal cycle was measured. The relationship between the parameters was measured and evaluated with a spectrophotometer device. Two-way mixed ANOVA and Post-hoc multiple comparison tests with Bonferroni correction were used for statistical analysis. ΔE values between 1-3.5 were considered clinically acceptable in this study. In our study, ΔE>3.5 was found in almost all samples. Only the PP group of Bio ZX2 and the P samples of Cube X2 were considered clinically acceptable compared to all other groups. Among group comparisons revealed that Cube X² zirconia under the G group had higher ΔE values than of Cube ONE zirconia (P=0.029). Bio ZX² zirconia under the P group had higher ΔE values than of both the Cube ONE and Cube X² zirconia (p<0.001) and both Cube ONE and Cube X² zirconia under the PP group had higher ΔE values than of Bio ZX2 zirconia(p<0.001). According to the within group comparisons, the highest to lowest staining values was obtained in the Bio ZX² group as G, P and PP groups, respectively (P<0.001). There was no significant difference between surface treatments in Cube ONE group (P>0.05). In Cube X² group, the highest staining value was found in G, PP and P groups, respectively (P<0.001). Based on the findings of this in vitro study, the following conclusions were drawn; the staining of translucent zirconia may be affected by different contents of yttria. The color was affected by both the glazing process and the polishing and polishing+paste cycle and exceeded the clinically acceptable color difference limit. Since preserving the color stability of translucent monolithic zirconia restorations used in the anterior region is aesthetically important, it is thought that the results of this in vitro study will inform the clinical selection of translucent monolithic zirconias, which are frequently preferred and newly developed in the anterior region, depending on their coloration potential.