Research of Optical Properties and Biocompatibility in Different Zones of Multilayered Translucent Zirconia on Hydrothermal Aging

Abstract

Objective: We assessed the changes in optical properties and biocompatibility of transition zones in multilayered translucent monolithic zirconia exposed to prolonged hydrothermal aging and compared the results to those with different yttrium oxide contents.

Materials and methods: Four types of zirconia blocks from IPS e.max ZirCAD were used: 3Y-TZP e.max ZirCAD LT (ZL), 4Y-TZP e.max ZirCAD MT (ZM), 5Y-TZP e.max ZirCAD MT Multi (ZT), and 3Y/5Y-TZP e.max ZirCAD Prime (ZP). A total of 120 specimens (15.0 mm diameter and 1.5 mm height) were fabricated and divided into three groups (n = 10). The aging process for the specimens was conducted in an autoclave set to 134 °C and 0.2 MPa, with durations of 0 h (control), 5 h (first aged), and 10 h (second aged). The optical properties and biocompatibility were analyzed, followed by a statistical analysis of the data (α = 0.05).

Results: Before and after aging, ZL and ZP exhibited the lowest color changes. ZT exhibited the highest average transmittance and translucency parameter values, while ZL had the lowest. The water contact angle test showed the highest value in ZM and lowest in ZL across all the aging stages. ZL, ZM, and ZP showed a considerable decrease in the water contact angle; however, ZT did not. A cell counting kit-8 assay showed ZL had the highest value, while ZM had the lowest. A filamentous actin test exhibited the highest value in ZL and lowest in ZM. In the vinculin analysis, ZL and ZT exhibited the lowest values, whereas ZM and ZP had the highest.

Conclusion: 3Y/5Y-TZP exhibited a balanced performance across critical parameters, such as color stability, translucency, and biocompatibility, aligning with 3Y-TZP. While 5Y-TZP demonstrated superior translucency, it confirmed the lowest color stability, whereas 3Y-TZP achieved the highest biocompatibility. These properties provide clinicians with a reliable material option that ensures superior esthetic outcomes and long-term prognosis, ultimately contributing to improved patient satisfaction and clinical longevity.

Keywords: biocompatibility; hydrothermal aging; optical property; surface property; yttrium oxide; zirconia.

Figure 1

The mean values of the color variations as measured by ΔE₀₀ (black background, SCI) of all the specimens in the groups. ZL, monolayered zirconia with 3 mol% yttria (3Y-TZP), IPS e.max ZirCAD LT; ZM, monolayered zirconia with 4 mol% yttria (4Y-TZP), IPS e.max ZirCAD MT; ZT, incisal zone of multilayered zirconia with 5 mol% yttria (5Y-TZP), IPS e.max ZirCAD MT Multi; ZP, transition zone of multilayered zirconia with 3 and 5 mol% yttria (3Y/5Y-TZP), IPS e.max ZirCAD Prime. All the data are presented as mean ± standard deviation values. * denotes a considerable difference at p < 0.05.

Figure 2

The mean values of the optical properties of all the specimens in the groups. (A) Average transmission; (B) translucency parameter; and (C) contrast ratio. ZL, monolayered zirconia with 3 mol% yttria (3Y-TZP), IPS e.max ZirCAD LT; ZM, monolayered zirconia with 4 mol% yttria (4Y-TZP), IPS e.max ZirCAD MT; ZT, incisal zone of multilayered zirconia with 5 mol% yttria (5Y-TZP), IPS e.max ZirCAD MT Multi; ZP, transition zone of multilayered zirconia with 3 and 5 mol% yttria (3Y/5Y-TZP), IPS e.max ZirCAD Prime. All the data are presented as mean ± standard deviation values. * denotes a considerable difference at p < 0.05.

Figure 3

AFM images of mean ± standard deviation values and statistical analysis of the surface roughness (R_a and R_q) of all the specimens in the groups. (A) ZLC, control group of ZL; (B) ZLAF, first-aged group of ZL; (C) ZLAS, second-aged group of ZL; (D) ZMC, control group of ZM; (E) ZMAF, first-aged group of ZM; (F) ZMAS, second-aged group of ZM; (G) ZTC, control group of ZT; (H) ZTAF, first-aged group of ZT; (I) ZTAS, second-aged group of ZT; (J) ZPC, control group of ZP; (K) ZPAF, first-aged group of ZP; and (L) ZPAS, second-aged group of ZP. ZL, monolayered zirconia with 3 mol% yttria (3Y-TZP), IPS e.max ZirCAD LT; ZM, monolayered zirconia with 4 mol% yttria (4Y-TZP), IPS e.max ZirCAD MT; ZT, incisal zone of multilayered zirconia with 5 mol% yttria (5Y-TZP), IPS e.max ZirCAD MT Multi; ZP, transition zone of multilayered zirconia with 3 and 5 mol% yttria (3Y/5Y-TZP), IPS e.max ZirCAD Prime. All the data are presented as mean ± standard deviation values. * denotes a considerable difference at p < 0.05.

Figure 4

HGF viability after IPS e.max ZirCAD aging. (A) The CCK-8 assay measured HGF quantity on the surface after 24 h of culture (p < 0.05, Tukey Test), and (B) live/dead assays were conducted 24 h post-cell-seeding, with live cells exhibiting green fluorescence due to calcein AM staining, and dead cells showing red fluorescence from ethidium homodimer-1. ZL, monolayered zirconia with 3 mol% yttria (3Y-TZP), IPS e.max ZirCAD LT; ZM, monolayered zirconia with 4 mol% yttria (4Y-TZP), IPS e.max ZirCAD MT; ZT, incisal zone of multilayered zirconia with 5 mol% yttria (5Y-TZP), IPS e.max ZirCAD MT Multi; ZP, transition zone of multilayered zirconia with 3 and 5 mol% yttria (3Y/5Y-TZP), IPS e.max ZirCAD Prime. All data are presented as mean ± standard deviation values. * denotes a significant difference at p < 0.05.

Figure 5

(A) F-actin area; (B) F-actin intensity; and (C) F-actin circ. (circularity). ZL, monolayered zirconia with 3 mol% yttria (3Y-TZP), IPS e.max ZirCAD LT; ZM, monolayered zirconia with 4 mol% yttria (4Y-TZP), IPS e.max ZirCAD MT; ZT, incisal zone of multilayered zirconia with 5 mol% yttria (5Y-TZP), IPS e.max ZirCAD MT Multi; ZP, transition zone of multilayered zirconia with 3 and 5 mol% yttria (3Y/5Y-TZP), IPS e.max ZirCAD Prime. All data are presented as mean ± standard deviation values. * denotes a significant difference at p < 0.05.

Figure 6

(A) Vinculin area; and (B) vinculin intensity. ZL, monolayered zirconia with 3 mol% yttria (3Y-TZP), IPS e.max ZirCAD LT; ZM, monolayered zirconia with 4 mol% yttria (4Y-TZP), IPS e.max ZirCAD MT; ZT, incisal zone of multilayered zirconia with 5 mol% yttria (5Y-TZP), IPS e.max ZirCAD MT Multi; ZP, transition zone of multilayered zirconia with 3 and 5 mol% yttria (3Y/5Y-TZP), IPS e.max ZirCAD Prime. All data are presented as mean ± standard deviation values. * denotes a significant difference at p < 0.05.