J Adv Prosthodont.  2017 Oct;9(5):394-401. 10.4047/jap.2017.9.5.394.

Comparison of the optical properties of pre-colored dental monolithic zirconia ceramics sintered in a conventional furnace versus a microwave oven

• Kim HK
• Kim SH

• KMID: 2393226
• DOI: http://doi.org/10.4047/jap.2017.9.5.394

Abstract

PURPOSE
The purpose of this study was to compare the optical properties of pre-colored dental monolithic zirconia ceramics of various thicknesses sintered in a microwave and those in a conventional furnace.
MATERIALS AND METHODS
A2-shade of pre-colored monolithic zirconia ceramic specimens (22.0 mm × 22.0 mm) in 3 thickness groups of 0.5, 1.0, and 1.5 mm were divided into 2 subgroups according to the sintering methods (n=9): microwave and conventional sintering. A spectrophotometer was used to obtain CIELab color coordinates, and translucency parameters and CIEDE2000 color differences (ΔE 00) were measured. The relative amount of monoclinic phase (X(m)) was estimated with x-ray diffraction. The surface topography was analyzed by atomic force microscope and scanning electron microscope. Statistical analyses were conducted with two-way ANOVA (α=.05).
RESULTS
There were small interaction effects on CIE L*, a*, and TP between sintering method and thickness (P<.001): L* (partial eta squared η(p)²=0.115), a* (η(p)²=0.136), and TP (η(p)²=0.206), although higher b* values were noted for microwave sintering regardless of thickness. Color differences between two sintering methods ranged from 0.52 to 0.96 ΔE(00) units. The X(m) values ranged from 7.03% to 9.89% for conventional sintering, and from 7.31% to 9.17% for microwave sintering. The microwave-sintered specimen demonstrated a smoother surface and a more uniform grain structure compared to the conventionally-sintered specimen.
CONCLUSION
With reduced processing time, microwave-sintered pre-colored dental monolithic zirconia ceramics can exhibit similar color perception and translucency to those by conventional sintering.

Keyword

Y-TZP ceramics; Color; Microwaves; Spectrophotometry

MeSH Terms

Ceramics*
Clothing
Color Perception
Methods
Microwaves*
Spectrophotometry
X-Ray Diffraction

Figure

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  Fig. 1 X-ray diffraction patterns of 6 subgroups at 2θ range between 20 to 40°.

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  Fig. 2 Atomic force micrographic images (10 µm × 10 µm) of the specimens by using conventional and microwave sintering methods.

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  Fig. 3 Scanning electron microscopy images (× 30000) of the specimens (1.5 mm thickness). (A) Specimen by conventional sintering, (B) Specimen by microwave sintering.

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