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ABSTRACT: The objectives of this study were to review the shade compatibility of esthetic restorative materials and to provide a visual method to harmonize the color of them.
Published reports on the color ranges and distributions of shade guides, color differences between restorative materials and the referenced shade guides, and those between the identical shade designated restorative materials were reviewed.
Several limitations in shade guides should be considered in color matching such as (1) color ranges and distributions of shade guides are different from those of human teeth, (2) arrangements of shade tabs in shade guides are not ideally logical, and (3) color of marketed esthetic restorative materials and the referenced shade tabs is significantly different. Color coordinates of restorative materials of the identical shade designations vary by the kind and brand of the restorative materials. Color differences between restorative materials and the referenced shade guides and those between the identical shade designated restorative materials are generally higher than perceptible limits. A visual color harmonization method was suggested, and the considerations for the instrumental color harmonization were provided.
Visual color matching would result in color mismatching by the kind and brand of the restorative materials. The first step to improve the color matching performance would be the harmonization of the color of restorative materials with those of the corresponding shade tabs.
Dental materials: official publication of the Academy of Dental Materials 12/2010; 26(12):1119-26. · 2.88 Impact Factor
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ABSTRACT: Optical properties of an object are determined visually or instrumentally. Although instrumental measurement provides objective and quantitative color coordinates, these values vary by the measurement method such as specimen and background conditions, instrument settings and illuminant. The objective of this study was to review the influence of the measurement method on the instrumental color coordinates of esthetic dental restorative materials.
Published reports on the measurement method dependent color variations of esthetic restorative materials were reviewed.
Surface roughness influences the color coordinates differently by the surface roughness range and the measurement geometry. Specimen thickness and the kind of illuminant influence the color coordinates, and the influence of background varied by specimen thickness. Therefore, the specular component excluded (SCE) geometry that reflects the surface condition of specimens is suggested as the correct measurement geometry. Surface roughness, thickness and layering of specimens, and the kind of illuminant should be stipulated in each measurement. There should be a standard for the color and gloss of the background.
Variables in instrumental color measurements should be stipulated to obtain consistent and comparable color coordinates, and a general guideline for instrumental color measurement of dental materials should be established.
Dental materials: official publication of the Academy of Dental Materials 11/2010; 26(11):1098-105. · 2.88 Impact Factor
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ABSTRACT: The enamel of natural teeth is opalescent, where there is light scattering of the shorter wavelengths of the visible spectrum, giving a tooth a bluish appearance in the reflected color and an orange/brown appearance in the transmitted color. The objective of this study was to determine the opalescence of all-ceramic core, veneer and layered specimens with a color measuring spectrophotometer.
Colors of core (A2-corresponding shade), veneer (A2- and A3-corresponding shades) and layered (A2- and A3-layered) ceramics for all-ceramic restorations in clinically relevant thicknesses were measured in the reflectance and transmittance modes. The opalescence parameter (OP), which was calculated as the difference in blue-yellow coordinate (Deltab(*)) and red-green coordinate (Deltaa(*)), and the differences in blue-yellow coordinate (Deltab(*)) and in color (DeltaE(ab)(*)) between the reflected and transmitted colors were calculated. One-way ANOVA was performed for the OP values of the core, veneer and layered specimens by the kind of materials. Regression analysis was performed between the OP and Deltab(*), and the OP and DeltaE(ab)(*) values.
The range of the OP value was 1.6-6.1, 2.0-7.1, 1.3-5.0 and 1.6-4.2 for the core, veneer, A2- and A3-layered specimens, respectively, all of which were significantly influenced by the kind of materials (p<0.05). The OP and DeltaE(ab)(*) values showed significant correlations within each of the core and veneer ceramics.
Opalescence varied by kind of ceramics. The OP values of ceramics were lower than those of tooth enamel. All-ceramic materials that can simulate the opalescence of natural teeth should be developed.
Dental materials: official publication of the Academy of Dental Materials 01/2009; 25(6):695-702. · 2.88 Impact Factor
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ABSTRACT: After staining a porcelain restoration, increasing the lightness (value) and decreasing the chroma of a restoration is not practically easy to accomplish.
The purpose of this study was to determine the color change of enamel porcelain after repeated external staining procedures over the enamel porcelain surface. Changes in translucency and differences in surface roughness were also measured.
Enamel porcelain (VITA OMEGA 900 Metal Ceramics) disks (1 x 12 mm) of 1 shade (EN2) were prepared, and 1 of 4 types of external stains (VITA Akzent stains) was applied over the specimens and fired. Firing was repeated 3 times after application of the same stains. Color of the specimens before and after stainings was measured with a reflection spectrophotometer. Two-factor repeated-measures analysis of variance with the fixed factors of the stain type and number of staining cycles for the changes in CIE L(*), CIE a(*), CIE b(*), color (DeltaE(*)(ab)), and chroma (DeltaC(*)(ab)) after repeated staining was performed (alpha=.05). Chroma change was calculated as DeltaC(*)(a)=(Deltaa *(2) +Deltab *(2))(1/2). Changes in translucency (translucency parameter and masking effect) and difference in surface roughness (Ra) after the third staining cycle were also determined.
Color change after the first staining cycle was perceptible (DeltaE(*)(ab) >2) for 2 of 4 types of stains and was perceptible for all 4 types of stains investigated after the third staining cycle (DeltaE(*)(ab) = 2.36-11.04). Lightness generally increased, and chroma also increased after staining but varied by the type of stains and number of staining cycles. Translucency generally decreased after repeated staining. Surface roughness varied by the type of stain (P < .001).
Color difference and lightness increased significantly after repeated staining cycles, but chroma change was small after repeated staining cycles. Therefore, repeated staining may be a method to increase the lightness of enamel porcelain.
Journal of Prosthetic Dentistry 07/2006; 95(6):437-43. · 1.32 Impact Factor
