Effects of Coloring Liquid Dipping Time and Surface Finishing Procedures on the Optical Properties of Monolithic Zirconia.

Background: Monolithic zirconia restorations can be produced from self-colored or uncolored blocks. The coloring procedure of uncolored blocks and surface treatments may affect the appearance of the restoration.

Aim: The purpose of this study is to evaluate the effect of liquid coloring and surface treatments on optical properties of translucent monolithic zirconia.

Methods: All specimens were cut from zirconia blocks with a thickness of 1 mm. Specimens were dipped in the coloring liquids for 3 min, 5 min, and 7 min and then divided into groups of 10 specimens for surface treatments. Glaze and mechanical polishing were applied, and the color of the specimens was measured under the D65 lighting condition with a spectrophotometer device. Color values obtained from the CIE Lab formula and the translucency parameter (TP), opalescence parameter (OP), and contrast ratio (CR) were calculated. The normality of the data was confirmed with the Shapiro-Wilk test. A three-way analysis of variance (ANOVA) was used to assess the effect of dipping time, liquid shade, and surface treatments.

Results: The effect of liquid shade and dipping time on the TP, OP, and CR parameters were statistically significant, and the TP values were reduced with the application of coloring liquid. Mechanical polishing groups had higher OP values and lower TP values than glazed groups.

Conclusion: In cases where high translucency is required, it may be advisable to use self-colored blocks and apply glaze as a surface treatment to achieve the desired optical properties.