Effect of the number of coloring liquid applications on the optical properties of monolithic zirconia.
OBJECTIVE
This study was aimed to investigate the effect of the number of coloring liquid applications on the optical properties of monolithic zirconia.


METHODS
Eighteen monolithic zirconia specimens (27.6 mm×27.6 mm×2.0 mm) were fabricated and divided into 6 groups (n=3). Each group was designated by the number of A2-coloring liquid applications (Group I to Group V) and Group O as a control. Color and spectral distribution of the specimens were measured with a double-beam spectrophotometer. CIE L*, a* and b* relative to the standard illuminants D65 were measured in reflectance and transmittance modes. Color difference (ΔEab*), translucency parameter (TP) and opalescence parameter (OP) were calculated. All measurements were performed on five different areas of each specimen. All data were analyzed by ANOVA and multiple comparison Scheffé test, Pearson correlations and linear regression analysis (α=0.05).


RESULTS
With the increase of the number of coloring liquid applications, CIE L* (R2=0.878) and OP values (R2=0.701) were decreased, but CIE b* (R2=0.938) was increased. However, TP values were not significantly changed. The color differences among groups ranged from 1.3 to 15.7 ΔEab* units. Strong correlation was found between OP and Δb* (R2=0.982, P<.01).


CONCLUSIONS
Within the limitations of this study, it can be concluded that the number of coloring liquid applications with a single shade affects the lightness, yellow chromaticity and opalescence of monolithic zirconia, although its translucency cannot be controlled by the coloring procedure.
Department of Prosthodontics, Veterans Health Service Medical Center, 6-2, Doonchon-dong, Kangdong-gu, Seoul, Republic of Korea; Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, 275-1, Yeongeon-dong, Jongno-gu, Seoul, Republic of Korea.
Hee-Kyung
HK
Kim
Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, 275-1, Yeongeon-dong, Jongno-gu, Seoul, Republic of Korea. Electronic address: ksh1250@snu.ac.kr.
Sung-Hun
SH
Kim
D003116:Color; D055095:Optics and Photonics; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared; D015040:Zirconium
D015040:Zirconium; C028541:zirconium oxide
Color; Opalescence; Spectrophotometry; Translucency; Zirconia-based ceramic