Development of Translucent Zirconia for Dental Crown Applications

Abstract

Zirconia-based dental ceramic is widely used for crown restoration, because of its superior mechanical properties and favorable biocompatibility. However, yttria-stabilized tetragonal zirconia (3YSZ), which is used in most dental crown restorations, has low translucency. This characteristic is unfavorable and results in low aesthetic quality of dental restoration. In this study, translucent 3YSZ dental ceramics were fabricated using nano-sized powder (20 nm) and high-temperature sintering (1500°C). The green bodies were slip casted and consolidated with cold iso-static pressing to create compact bodies. During the slip casting process different amounts of dispersing agent Polyethyleneimine (PEI) (0.2, 0.4, 0.6 and 0.8 wt%), were used to prevent agglomerates and create homogeneous suspensions. A minute amount (0, 0.1, 0.2, 0.3 and 0.4 wt%) of alumina was added into the suspension as sintering aid. The translucency or light transmittance of 3YSZ specimens was measured by an ultraviolet-visible spectrometer. Results showed that the 3YSZ specimen with 0.4 wt% alumina and 0.4 wt% PEI exhibited the highest light transmittance. The specimen also had larger grain size, because of excessive grain growth. The Vickers hardness of the specimens was insignificantly affected by the amount of alumina and PEI addition.

Effect of Different Glass-Ceramics and Resin Cement Curing Modes on the Color Stability of Sectional Laminate Veneers Following Artificial Aging.

“…Another explanation may be attribute to the scattering effect of the light as a result of the smaller particles size in Celtra press resulting in higher relative opacity when compared to e.max. 31 In current study, results showed that all samples L* values were decreased and a* and b* values were increased, indicating that decrease in brightness and tendency to become reddish and yellowish or to be darker after aging. These finding are similar to previous studies reported that ceramics get darker, reddish, or yellowish.…”

“…18,22 Nevertheless, the main cause for color change of the resin-cemented laminate veneers was the resin cement itself, due to the internal discoloration of the resin composite luting agents by hydrolysis reaction while the ceramic has the lowest effect on discoloration. 31,36 This might explain why the aging process had a greater effect on the restoration side than the natural side, as the restoration side has many interfaces of ceramic, resin cement and tooth itself and all of them are liable to discoloration.…”