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Table of Contents   
ORIGINAL RESEARCH  
Year : 2012  |  Volume : 23  |  Issue : 6  |  Page : 742-746
Vitapan 3D-master shade guide showed no fluorescence emission


1 Institute for Clinical Performance of Biomaterials and ETN Dental Clinic, Seoul, Korea
2 State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China
3 Department of Dental Materials and Center for Dental Materials, School of Dentistry, Kyung Hee University, Seoul, Korea

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Date of Submission17-Jun-2010
Date of Decision18-Oct-2011
Date of Acceptance21-Oct-2011
Date of Web Publication3-May-2013
 

   Abstract 

Objectives: To determine the fluorescence property of Vitapan 3D-Master shade guide tabs with a spectrophotometer.
Materials and Methods: Fluorescence property of 29 shade tabs, in both of original and ground-to-flat forms, was determined by a reflection spectrophotometer. Color difference (ΔE*ab-FL) by the inclusion and exclusion of the UV component of a standard daylight simulator (CIE standard illuminant D65) was calculated to determine the fluorescence color change. Fluorescence peak was expressed as the difference in spectral reflectance values by the UV component.
Results and Conclusion: ΔE *ab-FL values were in the range of 0.2 to 2.7 (mean: 1.2±0.6) for the original and 0.5 to 1.6 (mean: 0.9±0.1) for the ground-to-flat tabs, which was significantly different based on paired t-test (p<0.05); however, fluorescence peak was not detected in all the shade tabs. Therefore, fluorescence property of Vitapan 3D-Master shade guide should be modified to have similarfluorescence property of natural teeth and corresponding restorative materials.

Keywords: Fluorescence property, shade guide, spectrophotometer, standard daylight

How to cite this article:
Lee YK, Yu B, Lim HN. Vitapan 3D-master shade guide showed no fluorescence emission. Indian J Dent Res 2012;23:742-6

How to cite this URL:
Lee YK, Yu B, Lim HN. Vitapan 3D-master shade guide showed no fluorescence emission. Indian J Dent Res [serial online] 2012 [cited 2019 Dec 8];23:742-6. Available from: http://www.ijdr.in/text.asp?2012/23/6/742/111250
It has been traditionally assumed in dental field that fluorescence is the absorption of the ultraviolet (UV) radiation and the spontaneous emission of visible light, [1] since human tooth, specifically dentin, shows fluorescence emission, in which light in the UV range is absorbed and bluish visible light is emitted. [2] Therefore, color of a fluorescent object is influenced by the amount of the UV component in the incident light. A spectrophotometric method for the measurement of fluorescence property of esthetic dental materials by the inclusion and exclusion of the UV component of a standard daylight simulator was introduced. [1],[3]

Since the UV component of a light can brighten a fluorescent object such as human teeth[2] and fluorescent esthetic materials,[4] color of tooth and non-fluorescent restoration matched under the UV-excluded lighting condition would become not-matched when viewed under the UV-contained light.[1],[3] Therefore, differences in the fluorescence properties of dental objects would change the shade matching performance by the lighting condition.

Shade guides are used to identify and communicate the color of teeth and esthetic restorative materials. [5] Therefore, fluorescence property of shade guide tabs should match those of teeth and corresponding fluorescent restorative materials. As a systematically arranged shade guide, Vitapan 3D-Master (VITA Zahnfabrik, Bad Sackingen, Germany) is made up with six series of fired porcelain, built up with cervical, dentinal, and incisal powders, which are composed of feldspar nepheline and high-temperature ceramic pigments from the VITA family porcelains. [6] These six series consist of 29 shade tabs ranging from the lightest to the darkest lightness, from the lowest to the highest chroma and from yellow to red hue. The shade tabs in this shade guide are designated with 3-digit number and letter combinations. For example, for the 2M3 designation, the first number (2) indicates the lightness, the letter (M) indicates the hue, and the last number (3) indicates the chroma. As stated by the manufacturer, the letter L indicates yellow hue, M indicates middle hue and R indicates red hue. As compared with traditional shade guides such as Vita Lumin Vacuum (VITA Zahnfabrik) and Chromascop (Ivoclar Vivadent, Schaan, Liechtenstein), this shade guide resulted in improved color matching. [7],[8]

Color difference (ΔE*ab-FL) by the inclusion and the exclusion of the UV component of a standard daylight simulator was caused by fluorescence emission of an object. [1],[3] Therefore, clinical implications of this parameter on the optical performance of esthetic restorative materials have been studied. [1],[3],[4],[9] There was no such study for shade guides, although one previous study determined the fluorescence property of shade guides by detecting their fluorescence spectra under the action of UV ray. [10]

Fluorescence property of dental substances was previously determined with a spectrophotometer, [1],[3] which is designed to measure the color of flat surfaces. Fluorescence property of curved surface such as a shade tab measured by the spectrophotometric method would result in variations since it was reported that the color of shade guide tabs measured by a colorimeter or a spectrophotometer was inconsistent. [11] As a method to reduce these variations, it was reported that grinding the labial surface (ground-to-flat) of shade guide tabs resulted in more consistent spectrophotometric color values. [12]

The objective of this study was to determine the fluorescence property of Vitapan 3D-Master shade guide tabs by the fluorescence color difference (ΔE*ab-FL) and the spectral reflectance difference resulted by the inclusion and exclusion of the UV component of a standard daylight simulator [Commission Internationale de l'Eclairage (CIE) standard illuminant D65]. To determine the influence of grinding the shade tabs to make the measured surface flat on the fluorescence property, the fluorescence property of labial surface of the shade tabs was measured in both the original and 'ground-to-flat' forms. The null hypothesis assumed was that the fluorescence property of shade guide tabs would be similar to that of human dentin.


   Materials and Methods Top


Color in central portion of labial surface of the shade tabs in Vitapan 3D-Master shade guide was measured in original and 'ground-to-flat' forms. Ground-to-flat was performed by polishing a 5×8 mm 2 central portion of the labial surface up to # 2400 silicon carbide papers. Color of the central portion was measured because the translucency of the incisal edge would make the measured color background-dependent.

Color was measured according to the CIELAB color scale relative to the standard illuminant D65, under the UV component of a standard daylight simulator was 100% included and excluded conditions, using a reflection spectrophotometer (Color-Eye 7000A, X-Rite, Grand Rapids, MI, USA). The aperture size was 3×8 mm 2 and the illuminating and viewing configuration was the CIE diffuse/8-degree geometry with the specular component-excluded (SCE) condition. [13] External light was blocked by covering the tabs with a zero calibration box (Zero Calibration Standard, X-Rite) since the shape of the tabs at the back side was irregular; therefore, influence of ambient light on the measured color was eliminated. Measurements were repeated three times by repositioning the tabs for each measurement with the aid of a positioning jig.

Color difference (ΔE*ab-FL) by the inclusion and exclusion of the UV component was calculated with the equation: [13] ΔE*ab-FL=[(ΔL*) 2 +(Δa*) 2 +(Δb*) 2 ] 1/2 . From the spectral reflectance values of the tabs measured under the UV- included and -excluded conditions, the difference in each wavelength (400 to 750 nm range, 2 nm interval) by the UV component was calculated by subtracting the values of the UV-excluded condition from those of the UV-included condition. ΔE*ab-FL values between the original and ground-to-flat tabs were analyzed by paired t-test (α = 0.05, SPSS 12.0, SPSS Inc, Chicago, IL, USA).


   Results Top


Color differences (ΔE*ab-FL) are presented in [Figure 1] for the original tabs and in [Figure 2] for the ground-to-flat tabs. Color differences were in the range of 0.2 to 2.7 ΔE*ab units for the original and 0.5 to 1.6 ΔE*ab units for the ground tabs. Mean ΔE*ab-FL value for the original tabs was 1.2±0.6 and that for the ground tabs was 0.9±0.1, which was significantly different based on paired t-test (p<0.05).
Figure 1: Color difference (Δ E*ab-FL) by the inclusion and exclusion of the UV component for the original shade tabs of Vitapan 3D-Master shade guide

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Figure 2: Color difference (Δ E*ab-FL) by the inclusion and exclusion of the UV component for the ground-to-flat shade tabs of Vitapan 3D-Master shade guide

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Differences in the lightness (ΔL*-FL) by the inclusion and exclusion of the UV component for the original tabs are presented in [Figure 3], and those in the chroma (ΔC*ab-FL) are presented in [Figure 4]. They showed similar trends to those of the color differences. Mean subtraction spectra of each tab in the original form are presented in [Figure 5]. All of the shade tabs showed almost the same pattern, and none of them showed fluorescence peaks.
Figure 3: Difference in the lightness (ΔL*-FL) by the inclusion and exclusion of the UV component for the original tabs (Values under the 100%-UV -those in no-UV)

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Figure 4: Difference in the chroma (Δ C*ab-FL) by the inclusion and exclusion of the UV component for the original tabs (Values under the 100%-UV -those in no-UV)

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Figure 5: Subtraction spectra by the inclusion and exclusion of the UV component for the original tabs (Mean ± standard deviation of each shade tab)

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   Discussion Top


The null hypothesis of the present study that the fluorescence property of shade guide tabs would be similar to that of human dentin was rejected because fluorescence peaks observed in human dentin at the wavelength range of 440-460 nm [1] was not found in the shade tabs, although ΔE*ab-FL values of the tabs were in the range of 0.2 to 2.7 ΔE*ab units. In case of human dentin, ΔE*ab-FL value was reported as 0.7. [1] As to the ΔE*ab-FL values based on this previous study and our present study, direct comparison would be useless because the instrumental conditions were different. Although the shade tabs showed significant color differences by the UV component, they did not exhibit fluorescence peaks within the wavelength range of 400-750 nm [Figure 5]. Therefore, we concluded that shade tabs in this shade guide did not present fluorescence property. As to the ΔE*ab-FL values of the present study, combinations of the following causes might have caused these color differences such as the UV component of the standard daylight simulator and instrumental error. However, since the standard deviations for the differences in the color, lightness, and chroma were small [Figure 1], [Figure 2], [Figure 3] and [Figure 4], the influence of the UV component should have been the most significant.

For the evaluation of shade matching, instrument-based color difference values are routinely employed. However, there have been arguments on the threshold levels for the color difference that can be visually perceivable or clinically acceptable. One study found the threshold for an acceptable color difference was 1.7 ΔE *ab units, [14] while 3.3 ΔE *ab units were considered as an acceptable threshold in another study. [15] As to the perceptible limit, a color difference value of greater than 2 ΔE*ab units was perceived by 100% of the observers, and ΔE*ab units between 1 and 2 were frequently perceived. [16] As a clinical perceptible threshold, ΔE *abvalue of those ratings judged a perfect match was found to be 3.7 ΔE*ab units. [17] ΔE*ab value of 1 to 2 units was regarded as the perceptible limit in the present study because this value was based on translucent dental porcelains, [16] the composition of which was similar to that of the shade guide tabs investigated.

As to the ΔE*ab-FL values, they were in the range of 0.2 to 2.7 based on the original tabs. Since the experimental method for perceptibility determination [16] was different from that of the present study, the value of 1 to 2 ΔE*ab units should be regarded as a reference value. Applying this threshold (ΔE*ab>1), color differences by the UV component were perceptible in 18 tabs among the 29 original tabs, which implied that the color difference of shade tabs by the UV component of the standard daylight could influence clinical shade matching.

Although the color differences by the UV component were small in shade tabs, discrepancies in the fluorescence properties between dental objects such as shade tabs, teeth, and restorative materials would magnify the influence of fluorescence property on the shade matching under a daylight condition since the investigated shade tabs showed no fluorescence peaks while natural teeth and several restorative materials showed fluorescence peaks. [1],[2],[3],[4] In a previous study, [1] it was reported that the ΔE*ab-FL values were 1.6 to 2.4 ΔE*ab units in fluorescent resin composites that showed fluorescence peaks.

The amounts of the UV light in clinic, indoor environment, outdoor environment, and high UV lighting condition such as a dance club should be considered whether these color differences by the UV component of the standard daylight simulator would show practical implications. It was reported that the influence of the fluorescence emission in dental objects was more prominent under high intensity UV radiation such as in dance clubs, for actors or those whose social activities involve dance clubs or other environments that use UV radiation,[18] therefore, under these conditions, the clinical implications of the fluorescence properties would be augmented. Further studies on the discrepancy in fluorescence properties of dental objects under various lighting conditions should be performed.

The CIE standard illuminant D65 contains relative spectral power of 37 to 69% in the wavelength range of 330-395 nm (UV range),[17] although the UV light at 365 nm (or 363.8 nm) has been generally used to excite the fluorescence emission of dentin in previous studies.[4],[19] In these previous studies, a single wavelength in the UV region was used to excite the fluorescence emission. However, ambient light is not a monochromatic light; therefore, the use of the UV component of the standard daylight simulator could have higher clinical relevance. The merits of using the UV component of the standard daylight simulator to excite the fluorescence emission of dental objects would be that the influence of fluorescence emission on shade matching can be determined under the ambient daylight condition, not under artificial lighting conditions.

Among the methods specified in the ASTM specification,[20] the filter method, which compares spectral reflectance factors measured using a spectrophotometer under broadband illumination with that measured after adding filters to remove the fluorescence-excitation energy of illumination, was used in the present study. The confirmation of the presence of fluorescence can be made by the comparison of spectral reflectance curves at the wavelength of the maximum deviation, color difference or single parameter difference such as yellowness index or whiteness index.[20] In the present study, both of the color differences and existence of fluorescence peak by the UV component of a standard daylight were used.

Fluorescence property of the ground shade tabs was also measured in the present study because the original labial surface of the shade tabs is not flat. The discrepancy in the ΔE*ab-FL values between the original and the ground-to-flat tabs was caused by the translucent enamel layer. As reported previously, [12] the color difference resulting from the surface layer removal of the same shade guide was 1.4 to 5.9 ΔE*ab units. As indicated in a previous study, [21] the small-area colorimeter measures color parameters that result from the combined effects of both color and opacity in the case of a flat surface. However, for a curved surface like a shade tab, the influence of the aperture size on the color of translucent substances might be different. Based on a previous study, [12] the lightness, chroma, CIE a* and b* values of the shade tabs measured after the surface layer removal were higher than those of the original tabs except a few cases. Comparing the results of the present study, most of the original shade guide tabs showed higher color differences than the ground-to-flat ones. Increased color coordinates after the surface layer removal might have caused this discrepancy in the color difference values. However, in both conditions, no fluorescence peaks were observed.

Although the inclusion and exclusion of the UV component induced color difference in the shade tabs, none of the shade tabs showed fluorescence peak in the visible wavelength range of 400-750 nm [Figure 5], which might be a limitation of the Vitapan 3D-Master shade guide since natural dentin showed a fluorescence peak around 440 to 460 nm.[1] To impart fluorescence property to the shade tabs, fluorescent whitening agent (FWA) might be a candidate additive. FWA was added into resin composite in previous studies[22] to give fluorescence property because it is a chemical added to most fabrics and papers to increase color temperature, whiteness, and brightness. FWA accomplishes this effect by absorbing energy from the UV part of the light and emitting it in the visible blue light region around 450 nm.

The followings were limitations of the present study. Only one shade guide was used for the measurement. A previous study based on some old shade guide systems indicated that the same shade guide can contain different fluorescence components and two shade guides from the same source can have very different fluorescence. [10] However, the newly developed Vitapan 3D-Master shade guide tabs are made of the same materials by layering or combination of fired porcelain layers, and the fluorescence property is decided by the fluorescent dyes. [22] Therefore, it was supposed in the present study that no significant variations in fluorescence properties of shade guide tabs by the batch number. The shade tabs are approximately 8 mm mesio-distally and 11 mm inciso-cervically. Therefore, with the aperture size of 3×8 mm2 of the spectrophotometer, the spectrophotometer might have read broader than the middle portion, which might have influenced the color values. However, the influence was limited because the color of the same part of the shade tabs was measured with a positioning tool.

Within the limitations of the present study, the range of color differences by the UV component of the daylight simulator based on the original and the ground-to-flat Vitapan 3D-Master shade tabs was 0.2 to 2.7 ΔE*ab units; however, none of the shade tabs showed fluorescence peak. Therefore, the color difference by the UV component should be considered to enhance the accuracy of shade matching; besides, fluorescent whitening agent might be incorporated into shade tabs to simulate the fluorescence property of the teeth and the corresponding esthetic materials.

 
   References Top

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Correspondence Address:
Yong-Keun Lee
Institute for Clinical Performance of Biomaterials and ETN Dental Clinic, Seoul
Korea
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.111250

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