1. Influence of P2O5, AgNO3, and FeCl3 on color and translucency of lithia-based glass-ceramics
- Author
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Jacquelyn E. Moorhead, Kenneth J. Anusavice, and Nai-Zheng Zhang
- Subjects
Materials science ,Opacity ,Color difference ,Analytical chemistry ,Mineralogy ,Standard illuminant ,law.invention ,Physical property ,Tristimulus colorimeter ,Mechanics of Materials ,law ,Lithia ,General Materials Science ,Crystallization ,General Dentistry ,Hue - Abstract
Objectives . The objective of this study was to characterize the influence of various metals, metal compounds, and P 2 O 5 as a nucleating agent on the color and translucency of a Li 2 OAl 2 O 3 CaOSiO 2 glass-ceramic. Methods . Glass frits of Li 2 OAl 2 O 3 CaOCaOSiO 2 (LACS), LACS with 1 mol% P 2 O 5 (LACSP), and/or LACS with one of 16 colorants were melted, poured into a cylindrical graphite mold, cut into disks, annealed, nucleated, crystallized, and annealed again. Ten translucency measurements of each of five disks were made using a tristimulus colorimeter and a D65 standard CIE illuminant. The color of each disk was analyzed using the CIE L ★ a ★ b ★ color space system (1976) as a function of colorant, colorant concentration, and P 2 O 5 . Results . Mean L ★ values of glass-ceramic disks ranged from 63.5 for LACS containing 6.2 mmol% FeCl 3 (LACSP-6.2Fe) to 84.1 for LACS. No significant difference (p > 0.05) was found between the mean L ★ values for LACS, LACSP, and LACS with 0.19 mmol% AgNO 3 (LACS-0.19Ag). The mean contrast ratio of glass-ceramic specimens ranged from 0.42 (LACS and LACS-1.0Fe) to 0.98 (LACS-0.78Ag). Mean color difference values varied from 5.8 (LACSP-1.0Fe vs. LACS) to 36.3 (LACSP-0.78Ag vs. LACSP). Significance . The results of this study indicate that, because certain colorants in glass-ceramics affect opacity as well as hue and chroma, the development of glass-ceramics should be simplified by: 1) employing a nucleating agent that does not affect hue or chroma significantly, 2) controlling fixed levels of translucency consistent with mechanical and physical property requirements, and 3) varying the hue and chroma by means of colorants that do not affect the crystallization process. This implies that the volume fraction and mean size of crystals must be controlled, since the translucency or opacity of glass-ceramics is associated with scattering of light at the interfaces between adjacent crystals, and between crystals and the glass phase because of differences in refractive indices (McMillan, 1979a).
- Published
- 1994
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