Eur. J. Prosthodont. Rest. Dent., Vol.20, No.1, pp 23-25 Printed in Great Britain
© 2012 FDI World Dental Federation doi:10.1922/EJPRD_1012Khoshhal03
Accuracy of Shade Matching Performed by Colour Blind and Normal Dental Students Using 3D Master and Vita Lumin Shade Guides F. Vafaee*,V. Rakhshan*, M.Vafaei† and M. Khoshhal* The study was performed at Dental Research Centre of Hamadan University of Medical Sciences, Hamadan, and Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran. Abstract - The purpose of this study was to investigate whether 3D Master or VitaLumin shade guides could improve colour selection in individuals with normal and defective colour vision. First, colour perception of 260 dental students was evaluated. Afterwards, 9 colour blind and 9 matched normal subjects tried to detect colours of 10 randomly selected tabs from each kit and the correct/false answers were counted. Of the colour-defective subjects, 47.8% and 33.3% correctly detected the shade using 3DMaster and VitaLumin, respectively. These statistics were 62.2% and 42.2% in normal subjects. In normal participants, but not in colour blind ones, 3D Master significantly improved shade matching accuracy compared to VitaLumin. KEYWORDS: Shade matching, colour perception, colour blindness, dental shade guides
Introduction The correct shade of dental porcelain is important in the fabrication of aesthetic dental restorations 1-3. Defective colour vision has been reported in up to 9.3% in male dentists 4, 5 . Also, it was mentioned that the dentist who has defective colour vision, has the greater error in selection of hue and chroma, and the least error in value selection 6-9. Considering the aforementioned problem the 3D Master shade guide was designed as the base value10, although some authors investigated alternative shade guides 11, 12, . The purpose of this study was to investigate whether 3D Master or Vita Lumin shade guides could improve colour selection in individuals with normal and defective colour vision. The main reasons of dissatisfaction of the ceramic restorations are the difficulty in shade selection processes and inadequate information about the shade given to ceramist. The dentist’s shade matching ability depends on their knowledge of colour science and their colour vision healthiness 4, 6, 7. Nowadays, there are different shade guides on the international market, but Vita Lumin shade guide is most frequently used by Iranian clinicians because of its historical longevity. In 2003, Hammad indicated that the prosthodontists showed superior repeatability in shade selection than general practitioners13. It was also shown that repeatability of general practitioner’s colour selection was significantly improved using the Vita pan 3D Master rather than Vita Lumin vacuum. Ethell reported that there were no significant differences between colour defective and normal subjects in shade matching ability14. Although shade matching abilities of both groups were similar, the subjects with colour defective vision perceived that it was a slightly more difficult process 15.
* DDS † PharmD
The purpose of this study was to investigate whether 3D Master or Vita Lumin shade guides could improve colour selection in individuals with normal and defective colour vision.
Materials and methods In the first phase of this one-factor within-subjects clinical trial, all available dental students (145 men and 115 women) who were admitted to the Hamadan University of Medical Sciences during the years 2002 to 2007 were invited to be evaluated to find colour blind subjects. The inclusion criteria were subjects’ willingness to participate, absence of any significant systemic diseases, and being colour defective. Vision was examined by an optometrist in a standard condition and tested by Ishihara colour blindness test15. This test consists of plates (Ishihara plates) full of coloured dots appearing randomized in colour and size but placed in a way that a specific number would appear when colour blind (but not normal) people look at the plate. Each participant looked at 17 Ishihara plates from 75 cm distance, for 3 seconds and the observed numbers were used to diagnose colour-defective students15. After evaluating 260 students, 9 colour blind students were diagnosed. Nine normal-vision students matched for gender and age were then enrolled. In the second phase, a 3D Master shade guide was compared with Vita Lumin shade guide for shade selection by both healthy and colour-defective students. The similarity of the two shade guides was proved by laboratory tests. Twenty tabs of shade guides (10 tabs from 3D Master kit and 10 Vita Lumin tabs) were selected randomly their colour codes were covered by numbers from one to twenty. The tabs selected by each student were recorded. Shade selection was made in standard situations (in sunny days and in front of north window in the same dental unit located in prosthodontic department, between 11:00 and 13:00). Selected shades were compared with the original tab and the number of correct answers counted (n of trials = 2 kits
F. Vafaee, V. Rakhshan, M. Vafaei and M. Khoshhal
× 10 randomly selected tabs × 18 subjects = 360). The total number of correct shade determinations using each shade guide was recorded. McNemar and Pearson chi-square tests of SPSS statistical package (version 13, SPSS Inc., Chicago, US) used to analyze the findings at a significance level of 95%.
Results Nine colourblind individuals were identified (3.46% of 260 participants in the first phase). The prevalence of colour blindness in male students was 5.5% in males (8 men) and 0.87% in females (1 woman). Shade matching accuracy of colour-defective individuals using the 3D Master was 47.8%, but 62.2% for normal students. Shade matching accuracy for Vita Lumin was 33.3% and 42.2% for colour blind and normal students, respectively (Figure 1). McNemar test showed that the accuracy of shade matching using 3D Master and Vita Lumin shade guides were not significantly different for colour blind individuals (p = 0.093, Table 1). However, in normal students shade matching accuracy for 3D Master shade guide was significantly better than Vita Lumin (p = 0.009, Table 2). Pearson’s chi-square test indicated that the shade matching ability of normal students was significantly higher than that of colour-defective ones, when using 3D master guide (p = 0.049, Table 3). However, there was no significant difference between accuracy of these students when Vita Lumin shade guide was used (p = 0.220, Table 4).
Table 1. Net frequencies (and percentages) of correct and incorrect answers during trials done by colourblind subjects, divided based on the shade guides. Shade matching Correct Wrong
3D Master (%)
Vita Lumin (%)
43 (47.8) 47 (52.2)
30 ( 33.3 ) 60 (66.7)
Table 2. Net frequencies (and percentages) of correct and incorrect answers during trials done by normal subjects, divided based on the shade guides Shade matching Correct Wrong
3D Master (%)
Vita Lumin (%)
56 (62.2) 34 (37.8)
38 (42.2) 52 (57.8)
Table 3. Net frequencies (and percentages) of correct and incorrect answers during trials done by colourblind and normal subjects, using the 3D Master shade guide Shade matching Correct Wrong
Colourblind (%)
Normal (%)
43 (47.8) 47 (52.2)
56 (62.2) 34 (37.8)
Discussion Some studies suggest that healthy vision is important in shade selection in restorative dentistry. In this study, the accuracies of shade selection with 3D Master and Vita Lumin shade guides were measured after distinguishing colour blind participants. Defective colour vision might be congenital or acquisitive. The Acquired type equally affects men and women. However, the congenital type is recessive x-linked disorder. Therefore, it might be much more common in males. Its prevalence has been reported as 8% in men and only 0.64% in women5, which was consistent
Table 4. Net frequencies (and percentages) of correct and incorrect answers during trials done by colourblind and normal subjects, using the Vita Lumin shade guide Shade matching Correct Wrong
Colourblind (%)
Normal (%)
30 (33.3) 60 (66.7)
38 (42.2) 52 (57.8)
Figure 1. Frequency distributions (%) of correct colour selection by colour blind and normal subjects. 24
Running head: Shade matching accuracy
with the findings of this study (5% in males and 0.87% in females). Some studies link this disorder was related to ethnic and geographic locations and suggest its prevalence is different between races. Nevertheless, the results of Wasson et al. 4 did not underpin this theory.
Acknowledgment
The findings of this study indicated that the 3D Master and Vita Lumin did not have any statistically significant preference in colour-defective students. However, in the control group 3D Master assisted in more accurate shade matching than Vita Lumin. Hammad 13 has shown similar results in normal individuals.
Manufacturer Details
Shade matching accuracy of normal people using 3D Master shade guide was significantly for colour blind individuals (62.2% compared to 47.8%). This result suggests that an assistant who has normal vision can help the dentist to select a shade. The findings of Sproull,16 Barna et al.,17 and Davison and Myslinski 6 suggested a similar solution. Nevertheless, the accuracy of shade matching by Vita Lumin shade guide was not different between the two groups (42.2% for normal subjects compared to 33.3% for colourblind persons). On the other hand, plurality of tabs in 3D Master shade guide may make shade matching more difficult. This finding is similar to the study of Ethell et al. 14 who could not find any difference between two groups when they used Vita Lumin. Therefore, an assistant might not considerably help a colourblind dentist when they use Vita Lumin guide.
Dr Masoumeh Khoshhal, P.O.Box: 13185-1678, Tehran, Iran. E-mail:
[email protected]
The accuracy of shade selection of students in this study was low to moderate (between 33.3% and 62.2%) which might be attributed to low experience of students, as the accuracy of shade selection might improve by gaining experience18-21. In the present study, shade matching accuracy by normal students reported 42.2% for Vita Lumin. It was less than the rates observed by Tung et al.22 among experienced clinicians which were 55-64%. Colourblind students and dentists may make mistake in shade selection especially about hue and chroma. Vita Lumin shade guide is produced on the basis of hue which might cause difficulties for colour-defective dentists while selecting shades. Then, it is expected that the shade matching accuracy of Vita Lumin shade guide decreases for colourblind dentists. However there was not a statistically significant difference between these groups in this study. Clark 23 and Sproull 16 suggested value is the main parameter in shade selection. Colour blindness did not affect this parameter. Bergen and McCasland 24 and Barna et al.17 showed that environment light influences shade selection. Therefore, in this study shade matching was performed in the same condition.
Conclusion Within limitations of this study, the following conclusions were made: shade matching accuracy of colourblind students was less than normal subjects’ when 3D Master was used. In normal subjects, 3D Master shade guide significantly improved shade matching accuracy compared to Vita Lumin. In colourblind subjects, shade matching accuracy of 3D Master and Vita Lumin did not differ significantly.
We would like to express our sincere gratitude to Farzan Institute for Research & Technology for technical assistance.
The shade guides reported in this study were manufactured by Vita Zahnfabrik, Bad Säckingen, Germany.
Address for correspondence
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