Optical properties and flexural strength of translucent zirconia layered with high-translucent zirconia

Abstract

This study investigated the optical properties and flexural strength of translucent TZP layered with high-translucent PSZ using resin cement of various shades. Zirconia specimens (translucent TZP; Zpex and high-translucent PSZ; ZpexSmile) were 13 mm in diameter, layered at thickness ratios of 0.3/0.7, 0.5/0.5, and 0.7/0.3 mm (ZpexSmile/Zpex), and then luted using resin cement of 3 shades. Monolithic specimens of both were used as controls. CIE L*a*b* color coordinates and translucency parameter (TP) were evaluated as optical properties. Biaxial flexural strength was also determined as a mechanical evaluation. The a* and b* values of layered specimens varied depending on the shade of cement. TP values were not affected by shade of cement and thickness ratio. The biaxial flexural strength was intermediate value between both monolithic specimens. The layering method of zirconia with various translucencies using resin cement of different shades can improve color expression while maintaining clinically sufficient flexural strength.

Strength and aging resistance of monolithic zirconia: an update to current knowledge

“…Artificial aging had no effect on the flexural strength of either.- Prettau, Anterior- ICE ZirconKumchai et al (2018) [111]- inCoris TZIFlexural strength (3-point bending test), crosshead-speed of 0.5 mm min −1 .Overglazing significantly decreased the flexural strength.- Prettau- heat treated (glazed with no paste)Heat treatment had no significant effect on the flexural strength. There was no significant difference in the flexural strengths of different brands- Zirlux FC- overglazed (use of glaze paste)Two different glaze materials:- Zirkonzahn glaze paste + liquid- Zirlux FC glaze paste + liquidSakai et al (2019) [109]- translucent TZP (Zpex, Tosoh)Biaxial flexural strength, Monolithic zirconia materials of different tranclucencies were adhered and evaluated as a method for more accurate colour simulation.Flexural strength was not affected negatively.- high- translucency PSZ (ZpexSmile, Tosoh)Reis et al (2019) [80]Vita In Ceram YZNano-indentation (hardness evaluation), pulse-echo (elastic modulus), scratch testSilica infiltration increased the hardness but reduced the fracture toughness. Adhesion of feldspathic porcelain to non-infiltrated zirconia proved to be stronger- monolithic zirconia- silica infiltrated monolithic zirconia(via the sol-gel method)- zirconia + feldspathic porcelain of two thicknesses- silica infiltrated zirconia + feldspathic porcelain of two thicknessesJuntavee et al (2018) [96]Y-TZP, VITA YZ HT color®Flexural strength (3-point bending), crosshead speed 1 mm min −1 Increasedsintering temperature and prolonged sintering holding time was correlated with higher flexural strengthSintering at different temperatures:Sintered holding times:- decreasing- shortening…”

“…Compared to veneered specimens one study reported higher strength for bilayer [106] and another similar strength for trilayer specimens [108]. Sakai et al [109] reported that layering zirconia of various translucencies with resin cement between the layers is a method that improves the optical properties of the restoration while maintaining the flexural strength of the monolithic zirconia ceramic. Sulaiman et al [100,101] investigated the effect of staining on partially and fully stabilized zirconia specimens and reported a significant increase of strength for fully stabilized monolithic zirconia ceramics.…”

Monolithic Zirconia: An Update to Current Knowledge. Optical Properties, Wear, and Clinical Performance

“…A few studies have investigated the optical properties of monolithic zirconia and especially its TP and CR but the results are very inhomogeneous due to variations in instrumentation, zirconia brand, the thickness of the specimens and parameters evaluated (Table S1 and Table 1) [45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69]. For a comprehensive evaluation of the commercial products included in the following tables, their brand names and respective composition as reported by manufacturers or presented in associated references are presented in Table 1, at the end of the paper.…”

“…Differences were correlated to the larger grain microstructure of the multilayer zirconia. According to Sakai et al [69], when layering zirconia ceramics of different translucencies with the use of resin cements, TP values are not affected by the shade of the cement used or the thickness ratio of the different ceramics used.…”

Choice of resin cement shades for a high-translucency zirconia product to mask dark, discolored or metal substrates

“…It has also been found that 0.5-mm low-translucency zirconia ceramic could not mask tooth discoloration 14. An increase in thickness improves the masking ability of translucent zirconia 15. Nevertheless, Suputtamongkol et al16 demonstrated in a clinical trial that when luted onto a metal post-core, translucent zirconia crowns of < 1.5 mm thickness would still not match the color of natural teeth.…”