AESTETHIC DENTISTRY

EVALUATION OF POSSIBLE DISCOLORATION ON VITA CLASSICAL SHADE TABS USED DAILY COMPARED TO NEW REFERENCE SHADE TABS

¹Department of Prosthodontics, Faculty of Dentistry, Semmelweis University, Szentkirályi utca 47, Budapest, 1088-Hungary

aDMD, Assistant Lecturer; e-mail: dori.bpg@gmail.com ; ORCIDiD: https://orcid.org/0000-0002-3268-2478 bDMD, PhD, Associate Professor; e-mail: borbely.judit@semmelweis.hu ; ORCIDiD: https://orcid.org/0000-0003-3064-8724 cDMD, PhD, Professor and Head; e-mail: hermann.peter@semmelweis.hu ; ORCIDiD: https://orcid.org/0000-0002-9148-0139

Introduction Visual shade selection is still a very popular way of shade selection. This method is subjective with uncertain factors like the material of the conventional shade tab and restoration is different, the companies put different colored materials on the market under the same shade tab code. Besides these aggravating factors, the shade tabs can go under discoloration over time causing further difficulty in proper shade determination. This study aims to evaluate the extent of discoloration of the regularly used shade tabs by students in the Department of Prosthodontics. Methodology Six shades (A1, A2, A3, C2, C3, D2) were selected from nine regularly used VITA Classical shade guides (54 shade tabs in total) and compared visually and digitally (VITA Easyshade V spectrophotometer) to a corresponding brand-new reference guide. During the digital comparison L*a*b* values were recorded and the color difference (ΔE00) was calculated with the CIEDE2000 formula. Results 38 out of the 54 shade tabs were above the perceptibility threshold (0.8 ΔE00) and visual color changes were noticed as well. Unacceptable color differences ( above 1.8 ΔE00) were found in 19 cases. Only 16 shade tabs did not show visible and clinically relevant measurable discoloration. Conclusion Conventional shade tabs are worn off and go through discoloration over time. In this study, 70.4 % of the regularly used shade tabs went through noticeable discoloration. It is recommended to keep one new shade guide to verify the color of the regularly used shade tabs in the dental office.

Prosthodontics; Dental aesthetic; Color; Spectrophotometry; Discoloration.

Citation: Fehér D, Borbély J, Hermann P. Evaluation of possible discoloration on VITA classical shade tabs used daily compared to new reference shade

Received: February 14, 2024; Revised: February 25, 2024; Accepted: July 18, 2024; Published: August 08, 2024.

*Corresponding author: Dr. Dóra Fehér, DMD, PhD, Department of Prosthodontics, Faculty of Dentistry, Semmelweis University, Szentkirályi utca 47,

Budapest, 1088, Hungary, Tel.: +3614591500/59315; Fax: +3614591500; e-mail: dori.bpg@gmail.com

Copyright: © 2022 the Editorial Council for the Stomatology Edu Journal.

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2. MATERIALS AND METHODS

Selection of the shade tabs:

Nine layered ceramic VC shade guide (VITA Zahnfabrik, Bad Säckingen, Germany) was selected randomly from the practice rooms of the Department of Prosthodontics, Semmelweis University, the shade tabs are used by students (manufactured 1 guide in 2010, 4 guides in 2012 1 guide in 2013, and 3 guides in 2015 and all of them are original and produced by VITA Zahnfabrik). The reference was a brand-new VC shade guide provided by the manufacturer and manufactured in 2021. Based on a previous study the A1, A2, A3, C2, C3, and D2 are the most frequent natural tooth shades [8]. In this present study, these six shades were evaluated. (Fig. 2)

Figure 2. The six evaluated shade from VITA Classical shade tab.

Visual shade selection:

To provide standard lighting Smile Lite lamp (Smile Line, Switzerland) was used for visual shade determination. The Smile Lite lamp simulated the optimal 5500 K illumination for the correct tooth shade selection [9]. (Fig. 3)

Figure 3. Smile lite lamp (5500 K).

The visual shade selection was evaluated on the fact of the color difference between the used and the reference shade tabs but the degree of the color difference was not recorded. The observers, two dental students and one dentist who is an expert in dental shade selection went through the Ichihara test before the visual shade selection. (Fig. 4)

Figure 4. Visual comparison of the used and reference shade tabs.

Digital shade determination:

For digital comparison, a VITA Easyshade V spectrophotometer (VITA Zahnfabrik, Bad Säckingen, Germany) was used. The standardization of the lighting conditions was essential because the spectrophotometer measured the reflected light for this the shade tabs were evaluated in a dark box, through a little hole the same size as the tip of the spectrophotometer. To provide a standard position the shade tab holder was used. In the holder, the shade tab was positioned centrally with the help of a custom-made deep-drawn foil case (positioning foil). The holder with the positioning foil was placed in the dark box under the hole. (Fig. 5) To standardize the position of the spectrophotometer an acrylic stand was made to hold the device.

Figure 5. Positining the shade tabs .

One point measurement was made on every shade tab after calibration based on the instructions of the manufacturer. Every shade tab was measured three times. The spectrophotometer measures L*a*b* values. (Fig. 6) The L*a*b* values were recorded in an Excel file.

Figure 6. The VITA Easyshade V spectrophotometer measures L*a*b* values.

Calculating the color difference:

The ΔE shows the color difference between the used and the corresponding reference shade tabs. The color difference (ΔE00) was calculated with the CIEDE2000 formula. [10]

Where ∆L’, ∆C’, and ∆H are the differences in lightness, chroma, and hue. ∆R is an interactive term between hue and chroma differences. The weighting functions for the lightness, chroma, and hue components, respectively shown by SL, SC, SH. The kL, kc and kh parametric factors are correction

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Table 2. The number of shade tabs above 0.8 ΔE00 (PT50:50%) and 1.8 ΔE00 (AT50:50%) in the case of six shades.

The most deviations were found in the case of A1, A2, and C3, eight out of nine shade tabs were above the PT50:50% in all of these cases. In the case of C3 six shade tabs were also above the AT50:50%,in the case of A1 and A2 five and three shade tabs were found unacceptable (above AT50:50%) color difference. Categorization and Fisher’s exact test equivalent to the Chi-square test were done. The test showed that in the combined groups A1, A2, and C3 significantly (p=0.00056) worse outcome was noticeable than other shades in total. The three examined categories were combined on the basis that they have the lowest proportion of ΔE00 results indicating invisible color difference. (Figs. 8,9)

The ΔE00 of nine samples compared to the reference in every six shades are shown in Fig. 10. The perceptibility and acceptability thresholds are marked with an orange line. During the visual comparison, the observers found visible color differences in 38 cases.

4. DISCUSSION

Evaluation of the method of visual shade selection is a popular topic in dentistry. The most commonly used shade guide for visual shade selection is still the VC shade guide which contains 16 shades [14-16]. In dental practices to prevent cross-contamination the shade guides are disinfected regularly, [17] which can lead to changes in the shade [6,18]. Al Amri et al. evaluated the effects of the disinfectant liquid on VITA Lumin shade tabs with VITA Easyshade. In their study, 80% of the randomly selected shade tabs showed higher ΔE values than the perceptibility threshold [19]. In another previous study the effect of three disinfectants - Cavicide, Asepticare TB, and Sporicidin – was evaluated with a VITA Easyshade spectrophotometer on VC shade tabs [17]. The study evaluated two years of usage and based on the results the shade tabs did not undergo color changes in this period. Arrejaie et al simulated the effects of one, two and three years of disinfection with three different disinfectants on VITA Toothguide 3D Master shade guides. The measurements were carried out with A 7000A Colour Eye (X-rite, Grand Rapid, MI, USA) spectrophotometer [20]. Clinically significant color change was not described even after the three-year simulation, but the number of simulated disinfectant cycles was less than in other similar articles Hombesh et al evaluated the survivability of VITA 3D Master shade guides. The measurements were carried out with a spectrophotometer and two years were simulated. The test group was treated with isopropyl alcohol (70%), for the control group distilled water was used. A significant color difference was found between the control and the test group but without any clinical significance [6]. Alshetri et al treated the VC shade tabs with a disinfectant containing 70% ethanol and isopropyl alcohol. The potential color difference after the disinfection was evaluated digitally (Shade Eye NCC colorimeter) and visually [18]. Discoloration on the shade tabs was found in the case of 17.8% after two years of simulation, after three years it was raised to 28.9%. Pohjola et al found increased L* (lightness) and c*(chroma) values after two and three years of simulated disinfection with Cavicide disinfectant [21]. Alsethri and Pohjola both recommend keeping one reference shade guide in the dental office to check the color of the frequently used shade guides regularly [18,21]. In this present study the potential discoloration of the shade tabs - used by students in the Department of Prosthodontics, Semmelweis University - was evaluated due to everyday usage. During the visual comparison a visible color difference was found on 38 shade tabs. The color difference was not commeasurable, but the transparency of the edges was less visible on the used shade tabs compared to the new reference. (Fig. 11,12) Regarding the C2 shade tabs the best result was observed because discoloration was only found in two cases. (Fig. 13)

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REFERENCES

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DMD, PhD Department of Prosthodontics Faculty of Dentistry Semmelweis University CV Budapest, Hungary

Dr. Dóra Fehér is a PhD student andbecame a prosthodontist specialist in 2022. She has been working in the Department of Prosthodontics, at the Semmelweis University since 2019. Her PhD is about the possibilities of shade reproduction andinvestigates the shade matching of the shade tabs and restorative materials and the color stability and discoloration of conventional shade guides. Its aim is to provide patients with the best aesthetic outcome by reproducing the correct shade and translucency with modern ceramic materials. Besides her research activities, she teaches prosthodontics at the university for dental students and participates in the education of post-graduation students, dental assistants, and dental technicians as well.

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1. What are the most commonly used shade guides?

3. What is the color temperature of the Smile Lite lamp?