Effect of polishing and glazing on the color and spectral distribution of monolithic zirconia.
OBJECTIVE
The aim of this study was to evaluate the effect of polishing and glazing on the color and spectral distribution of monolithic zirconia.


METHODS
Forty-five monolithic zirconia specimens (16.3 mm × 16.4 mm × 2.0 mm) were fabricated and divided into 5 groups according to the number of A2-coloring liquid applications (Group I to V). Each group was divided into 3 subgroups according to the method of surface treatments (n=3): N: no treatment; P: polishing; G: glazing. Color and spectral distribution of five different areas of each specimen were measured according to CIELAB color space in the reflectance mode relative to the standard illuminant D65 on a reflection spectrophotometer. Data were analyzed using one-way ANOVA followed by Tukey's HSD test, Pearson correlation and regression analysis (α=.05).


RESULTS
There was a significant difference in CIE L (*) between Subgroup N and P, and in CIE b (*) between Subgroup P and G in each group. Spectral reflectance generally decreased in Subgroup P and G in comparison with Subgroup N. Color differences between Subgroup P and G were within the perceptibility threshold (ΔE (*) ab< 3.7) in most groups. Highly significant correlation was found between CIE b (*)and each subgroups as the number of coloring liquid applications increased (R (2)>0.88, P<.001).


CONCLUSIONS
A perceptible color difference can be detected after polishing of monolithic zirconia. Polishing decreases the lightness, and glazing also decreases the lightness, but increases the yellowness of monolithic zirconia.
Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
Hee-Kyung
HK
Kim
Sung-Hun
SH
Kim
Jai-Bong
JB
Lee
Jung-Suk
JS
Han
In-Sung
IS
Yeo
Color; Dental polishing; Surface properties; Zirconia-based ceramic