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Performance of Dental Students in Shade
Matching: Impact of Training
ADRIANA P. BUHRER SAMRA, DD*, MARCELLA G. MORO, MD
†
, RUI F. MAZUR, PhD
‡
, SERGIO VIEIRA, PhD
§
,
EVELISE M. DE SOUZA, PhD
{
, ANDREA FREIRE, PhD**, RODRIGO N. RACHED, PhD
††
ABSTRACT
Objective: The present study evaluated the effec t of training on dental students’ability for matching t wo different shade
guides.
Materials and Methods: The study was conducted in 2012.The participants were 88 male and female undergraduate
dental students from Brazil and Portugal, with or without previous color education and vision refractive errors
(response rate of 73.33%).They were asked to match a pair setof the shade guides Vita Classical (VC) and Vitapan 3D
Master (3DM), with a 20-minutes’rest between each match.The sets were assembled over a neutral gray
background and under controlled light. About 7 ^10 days later, allp articipants watche d a video lecture on color
education and repeated the matching procedure.The percentage of matche s was calculated and submitted to
statisticalanalysis for the variables gender, geographic region, shade guide and previous color education
(Mann ^Whitney tests), vision refractive errors (Kruskal^ Wallis), and training ( Wilcoxon signed rank). All test s were
per formed at a conf|dence level of 95 %.
Results: Trainingincreased the percentage of matches for allgroups, exceptfor Portuguese and hyperopic individuals
(VC and 3DM) and men (3DM). Previous color education affected VC shade matching before training.Gender,
refractive errors, and geographic region did not affect shade matching ability.
Conclusions: Previous education and training in color positively affected shade-matching abilityof dental students on
shade guide pairing tests.
CLINICAL SIGNIFICANCE
The subjectivityof the visual method might not be a clinical concernin daily practice.The human eye can detect small
differences in color and visualize the tooth with allits complexgeometry, multilayered tissues, and secondary color
parameters. Therefore, any color-matching task will be judged by the patient and/or other observers with
consideration to this complexity.In other words, visual assessment is paramount to the success/failure of esthetic
restor ative pro cedures.T he eff|cienc y of the visual color method may b e improved by color educ ation through the
developmentof professional colordiscrimination ability.This would make the students responsible for color selection,
reproduction, and evaluation and lead to increased capability over a layperson observer receiving the restorative
treatment.
*Assistant Professor, Department of Dentistry, Universidade Estadual de Ponta Grossa, Ponta Grossa, Brazil
Post-Graduate Student, Department of Periodontology, Universidade de S~
ao Paulo, S~
ao Paulo, Brazil
`
Professor, Scho ol of Life Sciences, Pontifi
cia Universidade Cat
olica do Paran
a, Cu rit ib a , Bra zil
‰
Professor, Scho ol of Life Sciences, Pontifi
cia Universidade Cat
olica do Paran
a, Cu rit ib a , Bra zil
Professor, Scho ol of Life Sciences, Pontifi
cia Universidade Cat
olica do Paran
a, Curitiba, Brazil
**Professor, School of Life Sciences, Pontifi
cia Universidade Cat
olica do Paran
a, Cu rit ib a , Bra zil
Professor, Scho ol of Life Sciences, Pontifi
cia Universidade Cat
olica do Paran
a, Curitiba, Brazil
Journal of Esthetic and Restorative Dentistry Vol 00 No 00 00^00 2017
V
C2017 Wiley Periodicals, Inc. D O I 1 0 .1111/jerd.12287 1
CLINICAL ARTICLE
INTRODUCTION
Color selection is a challenge in daily dental practice.
1,2
To be successful, clinicians must understand color,
light source, surface, and structural characteristics of
both the tooth and restorative material,
3
as these may
interfere with optical properties and light reflection,
refraction, absorption, and/or transmission capacity.
4,5
Visual and instrumental methods for color assessment
are widely described in the literature.
6–9
However, in
dental practice, there is no consensus on an ideal
method. Instrumental assessment should still be used
as an adjunct rather than a replacement for visual
assessment,
3
as it does not consider some
characteristics inherent to the dental environment,
such as the complex geometry of the teeth, surface
texture,
10
translucency and color variations, and the
influence of the background and thickness, as well as
the illuminant and angular subtense.
11
On the other
hand, visual perception is subjective and dependent on
brain physiology, psychology,
12
eye fatigue,
13
age,
experience,
14
ambient lighting,
15
and observer color
vision deficiency.
13
While the human eye can detect small color differences,
7
theinfluenceofcertainfactorsonvisualassessment
remains unclear. Gender has been implicated in many
studies
3,9,14
as one of the most important factors that
could interfere in visual selection, and although it has
been widely investigated, it remains controversial.
14,16
Cultural factors and socio-demographic factors have been
also been implicated, with tooth color as the major factor
in dental esthetics.
13
The influence of esthetic patterns,
as individualized
17
as they are, and/or their correlation
with cultural
17
and educational background, has not been
investigated. Although myopia affects one-third of the
global population,
18
the literature remains scarce on the
impact of vision refractive errors on color selection.
19
Visual shade has historically been selected by means of
comparison with the aid of shade guides. The
empirically based Vita Classical (VC) (Vita ZahnFabrik,
Badsackinger, Germany) chart
7
was considered the
“gold standard,” and to a large extent, it still is.
6
However, the introduction of the Vitapan Toothguide
3D-Master (3DM) (Vita ZahnFabrik, Badsackinger,
Germany) has allowed for comparatively adequate
distribution of the three dimensions of the color on
the color space of the natural tooth.
8
The importance
of color in dentistry, narrowness of the tooth color
range, and the availability and familiarity of shade
guides
13
suggest matching pairs of shade guide tabs for
the evaluation of color discrimination competency in
dentistry, in accordance with the Technical Committee
106 of the International Organization for
Standardization in the ISO/TR 28642.
13,20
The shade
guides match tabs test is considered a parameter of
color assessment ability.
5
The effectiveness of training on visual color assessment
has been demonstrated.
21
Web programs and online
training systems,
22
including toothguide training (TT)
software
21
and toothguide box (TTB),
21
seem to be a
trend. These systems allow for data storage and easy
access to all dental students, professionals, and
technicians with a well-known protocol.
22
However,
the direct impact of a color education lecture on the
development of visual assessment ability has not been
investigated.
Therefore, the aim of this study was to evaluate the
effect of training dental students in Brazil and Portugal
on a shade-matching tabs test using two shade guides.
In addition to training and geographic region, color
match percentage was evaluated as a function of
gender, refractive errors, previous education, and shade
guides.
The null hypotheses tested were as follows: there
would be no differences on percentage of matches (1)
as a function of gender, refractive errors, geographic
region, previous education, and shade guide or (2) as a
function of experimental times, that is, before and after
training.
MATERIALS AND METHODS
All undergraduate students in the third, fourth, and
fifth grades of the Dental Undergraduate Program at
the Universidade Estadual de Ponta Grossa (State
SHADE GUIDE MATCHING Samra et al
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C2017 Wiley Periodicals, Inc.2
University of Ponta Grossa—UEPG; Brazil) and
Faculdade de Medicina Dent
aria da Universidade do
Porto (Faculty of Dental Medicine at University of
Porto—FMDUP; Portugal) were invited to participate.
Subjects recruited were 120 volunteers who signed an
informed patient consent form following approval of
the institutional ethics committee (#109.845). Subjects
performed the Ishihara Color Vision Test
21,23–25
before
taking part in the experiment, and one male student
who presented with visual chromatic deficiency was
excluded. Thirty-one volunteers who were not able to
provide all the information required prior to the
experiment (ophthalmologist data, use of prescription
glasses, or lenses) were excluded.
The inclusion criteria were third-, fourth-, and fifth-
grade undergraduate dental students from both
universities, ophthalmologic appointment within the
last year, corrective eyeglasses or lenses when myopia
or hyperopia were present. The exclusion criteria were
visual chromatic deficiency detected by Ishihara Color
Vision Test and presence of uncorrected myopia and
hyperopia.
The final sample (N588) consisted of 26.14% male
and 73.86% female dental students; 60.23% had normal
vision, while 32.95% were myopic and 6.86% hyperopic;
72.73% were Brazilian and 27.27% were Portuguese.
Subjects’ age ranged from 20 to 26 years. Previous
color education was received by 69.32% of participants,
leaving 30.68% without prior education.
Two commercial shade guides, Vita Classical (VC) and
Vitapan 3D Master (3DM), were selected for the
experiment.
6,8,15
The participants were asked to match
a pair set of each shade guide. To compare all the
extent of the color space of both shade guides, all
shades were selected. The sets were placed on a table
over a neutral gray (18% reflectance) background
6,14,19
and under controlled light conditions (D65
illuminant,
13,25
6,500 K lamp,
2,24
90% color rendering
index) that simulate average natural daylight.
11
Each
shade tab had its color code hidden by a plastic
cap,
4,13,24,25
but all tabs of one set had an identification
rubber to ensure the pair had one tab from each set.
Subjects were oriented to match the shade tabs
without any further communication or time
restriction. Subjects paired the shade guides in
interleaved order, with 20-minute intervals in between
to prevent eye fatigue.
23
The test was completed
between 9:00 a.m. and 3:00 p.m., and subjects were
asked not to perform any other tasks prior to the test
in order to avoid eye fatigue.
Within the 7–10 days following the first color-
matching phase, all subjects watched a 50-minute
video lecture on color education.
9,23
The video lecture
considered color attributes, importance of color
matching, color-selection techniques using visual
assessment, spectrophotometers, and the VC and 3DM
shade guides. It was presented by one of the authors
and recorded at UEPG. Within 7 days after watching
the lecture, subjects completed the second color-
matching phase under the same controlled conditions.
Descriptive analysis of the percentage of exact matches
of all tabs for both shade guides was calculated, and
data were analyzed with SPSS 20.0 (IBM, Chicago).
Data were tested for normality using the Kolmogorov–
Smirnov test and homogeneity using Levene’s test.
The difference in the percentage of matches before
and after the video lecture (effect of training) was
analyzed using Wilcoxon signed rank test. The
difference in the time (minutes) before and after
training was analyzed using Wilcoxon signed rank test;
as well, to compare the difference in the time in Brazil
and Portugal, Mann–Whitney U-test was performed.
Gender, refractive errors, geographic region, previous
education, and shade guide were analyzed for
differences in the percentage of matches using Mann–
Whitney U-test (gender, geographic region, previous
education, and shade guide) and Kruskal–Wallis
(refractive errors). All tests were performed at a
significance level of 5%.
RESULTS
There was a significant increase in the overall
percentage of matches following training for both
SHADE GUIDE MATCHING Samra et al
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shade guides. No significant differences were detected
between the shade guides regarding all the variables
tested (p>0.05) (Table 1).
Women, subjects with normal vision and myopia,
Brazilians, as well as subjects with and without
previous education revealed a statistically significant
increase in the percentage of matches following
training (p<0.05) for VC (Table 2) and 3DM (Table
3) shade guides. Men showed an increase after training
only for VC (p<0.05).
Before and after training there were no statistically
significant differences between gender, refractive error
type, or geographic region in shade matching
percentage (p>0.05) for VC (Table 2) and 3DM
(Table 3). However, before training, there were
significant differences in the percentage of matches of
VC for the factor previous education (p<0.05).
When the times were compared before and after
training, statistically significant difference was
found at 3DM Brazil group (p<0.05). On the other
hand, when both countries were compared, a
statistically significant difference was found between
all values (p<0.05), except to 3DM after training
(Table 4).
DISCUSSION
The results permitted the rejection of null hypothesis
1, as there were differences in the percentage of
matches as a function of previous education for VC.
Null hypothesis 2 was also rejected, as training affected
the percentage of matches for all variables.
Shade guide pairing contributes to evaluation of
dentists’ visual assessment ability.
13
Vita Classical and
Vitapan 3D Master were selected in the present study
because they are the most used shade guides in
dentistry.
6,15,26
Previous studies have evaluated only
some tabs of the shade guides (3DM;
9,13,24
VC;
25,27
VC
and 3DM
21
). The present study evaluated all tabs of
both shade guides, which aided to detect the
fundamental shade-matching ability of the subjects.
4
Overall, in the present study, the percentage of
matches was similar for both shade guides. Previous
studies showed participants to perform better in color
matching
1,26
and in color replication ability
1,8
with
Vitapan 3D Master than with Vita Classical.
The effect of gender on color selection is controversial
in the literature. Some studies have reported no
differences
9,13
between males and females, while others
detected gender effects.
15
It had been reported that
women have better chromatic perception, especially
for red-green stimuli,
28
while men demonstrate better
lightness perception.
14,29
In the present study, subjects
were challenged to match a large range of hues and
lightness instead of specific tabs that could benefit one
or other gender. For instance, the A, B, and D tabs of
VC shade tabs and the right-side tabs (reddish hues) in
3DM could benefit women. Yet, the 3DM three-step
method, which is based on lightness, could benefit
men.
14,29
This might explain the no effect of training
on men pairing 3DM, as they may have benefited at
the initial evaluation. Overall, major physiological
variations between individuals in the central visual field
could mask gender differences.
28
Previous studies have
shown considerable variability between individuals,
30
even intra-group variability.
29
The present study showed no effect of vision refractive
error on color matching. The ability to discriminate
colors with different wavelengths may be affected by
vision refractive errors,
19
as myopic subjects have
longer eyeballs with light rays focused in front of the
retina, whereas hyperopic subjects have the opposite
abnormality.
18
Red/green matches decrease among
subjects with myopia, while brightness level remains
normal.
31
This could be attributed to red sensitivity,
due to prevalence of L-cones and accommodation,
31
TABLE 1. Shade-matching percentage (mean and standard
deviation) before and after training for Vita Classical (VC) and
Vita toothguide 3D Master (3DM) shade guides
Shade
guide
Before
training
After
training
p
value
VC 64.0 6 622.46 76.64 620.93 0.00 0
3DM 63.59621. 27 71.59 619.7 9 0. 0 02
pvalue 0.608 0.821
SHADE GUIDE MATCHING Samra et al
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thus presenting an issue with visual color matching for
myopic observers, at least for shades A, B, and D on
VC and the right-side tabs on 3DM.
One of the inclusion criteria was the use of glasses or
contact lenses during test execution, as well as having
had an ophthalmologic appointment in the previous
year for those with refractive errors. Although some
effect on shade-matching ability might be expected,
even with correction, it seemed to be negligible, in
agreement with previous study.
19
It can be assumed
that if subjects with refractive errors did not wear
corrective glasses or lenses, the results might be
different. However, when the effect of training was
evaluated, the results of hyperopic students did not
improve, whereas those of subjects with normal vision
and myopia did. This is probably attributed to a
limited sample size (n56). There is a low prevalence
of hyperopia in the population, varying from 6.3% to
19.3%.
18
This indicates the difficulties with forming a
balanced sample, and it is a limitation of the present
study.
Dental students are considered an appropriate
population to test shade-matching abilities, as they
form a uniform group of young adults with fewer
systemic conditions that affect color perception, and
yet, little or no experience with shade selection.
4
To
investigate dental students from different countries in
different geographic regions (hemisphere, climate, light
spectrum peculiarities) with distinct cultural and
educational backgrounds allowed for unique
TABLE 2. Shade-matching percentage (mean and standard deviation) before and after training for Vita Classical shade guide
Variable n
Before
training
After
training
Gender p value
Male 23 62.8 622.3 79.6619.6 0.004
Female 65 64.5 622.6 75.6 621.4 0.000
pvalue 0.757 0.431
Refractive error
Normal vision 53 63.5 623.3 75.6 620.3 0.001
Myopic 29 65.7 621.1 79.3 620.1 0.001
Hyperopic 660.5623.5 73.0 631.3 0.144
pvalue 0.824 0.723
Geographic region
Brazil 64 61.4 622.1 76.3 620.9 0.000
Portugal 24 71.2 622.1 77.5 621.3 0.147
pvalue 0.062 0.731
Previous education
Without 27 56.6 621.0 70 .8 624.2 0.002
With 61 67.3 622.3 79.2 618.7 0.000
pvalue 0.039 0.083
pvalueindicates differencesb etweenmeans for before and after training (rows) and foreach variable’s level (column).
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comparisons of shade-selection ability. Moreover,
multicenter studies provide high reliability of results.
21
It is interesting to note that, despite the above-stated
differences, subjects’ performance was similar across
countries, strengthening the present findings.
Moreover, any complementary natural light that could
have reached the room,
32
including differences in light
intensity and spectrum peculiarities due to
geographical location, might not have had any impact
on the color matching of the students.
Previous education affected VC shade matching, which
explains why third-grade students, without any prior
color education, had a significantly lower percentage of
matches than did other students, who had taken at
least one class and delivered prosthesis to patients at
their universities. There is consensus on the effect of
color education on color matching.
12,21,22,26
In spite of
this, color education is lacking
26
in dental education
programs.
4
The majority of dental students from 15
different European dental schools stated that they
wanted digital color education added to their
curriculum.
26
The American Dental Association’s
Survey Center revealed that only 4.8% of dental
education is dedicated to esthetic dentistry, while
details about educational components, such as color
science, shade selection techniques, and protocols are
not available.
4
Training had a positive effect on tooth shade matching
for VC and 3DM.
21,23
In the present study, a 50-
minute lecture developed and presented by one of the
TABLE 3. Shade-matching percentage (mean and standard deviation) before and after training for Vita toothguide 3D Master
Variable n
Before
training
After
training
Gender p value
Male 23 64.3 623.6 74.5 623.7 0.050
Female 65 63.3 620.6 70.6 618 .4 0.020
pvalue 0.787 0.312
Refractive error
Normal vision 53 65.2 621.8 7 2 . 5 620.0 0.043
Myopic 29 61.5 618. 8 71.4 617.0 0.009
Hyperopic 659.6630.1 64.7 631.1 0.673
pvalue 0.724 0.842
Geographic region
Brazil 64 61.9621.7 7 3. 2 620.4 0.000
Portugal 24 67.9 619. 8 6 7.3 617.7 0.951
pvalue 0.288 0.160
Previous education
Without 27 58.8 621.1 7 3. 2 618.1 0.002
With 61 6 6 . 2 620.6 71.9 619.1 0.040
pvalue 0.128 0.770
pvalueindicates differencesb etweenmeans for before and after training (rows) and foreach variable’s level (column).
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authors was used to train the subjects, similar to
previous studies,
9,23
which used a lecture about color
that was either associated or not to other programs.
The exercise itself must be considered part of training
program, as though it takes part in learning process.
Besides that, the matching procedure performed twice
may be part of the learning spiral reciprocating theory
and practice making results better.
33
Hence, the
exercise itself aids the training process, so it could not
be separated from the lecture. So, in this study design,
it was not possible to select a control group, since the
exercise had to be performed by all the subjects and in
both experimental times. Thus, any attempt of control
group could result in bias, jeopardizing the research.
In this study, training improved color match
percentage for all groups except Portuguese
individuals, those with hyperopia, and male (VP shade
only) students.
The fact that training had no effect on color-matching
skills on Portuguese students may be explained by
curriculum differences between universities. While all
Portuguese students had previous knowledge of
“color,” and had attended classes about “color
selection,” only the fourth- and fifth-grade Brazilian
students had previous education on this theme.
Further, while both countries share the same language,
they differ in vocabulary, grammar, spelling, and
accent, which could possibly jeopardize the
effectiveness of the lecture, which was presented in
Brazilian Portuguese, what could be considered a
limitation of this research. Moreover, the analysis only
considered the increase in exact matches. It is possible
that the color difference (DE) between paired tabs after
training decreased. This would represent learning that
could not be detected with this methodology. These
results suggest that color education might increase the
percentage of matches and develop shade-matching
ability with a 50-minute lecture.
Overall, the mean percentage of matches in this study
varied from 56.6% to 79.7%. Bahanann
9
found a mean
percentage of matches of 36.3% with the visual
method. This difference could be attributed to
differences in methodology. Whereas in the present
study, subjects matched all the tabs of both shade
guides, Bahanann evaluated the combination of one
natural tooth with the closest match in the shade
guide. When comparing percentage of matches using
only shade guides or using shade tabs comparing with
natural teeth, similar results for both situations have
been found in simple and moderate clinical cases.
4
Moreover, the present study deals with synthetically
materials and the color match of natural teeth may be
much more complex, due to its inherent optical
properties. However, for subjects to be considered
competent in color discrimination, matching
parameters
13
have been established as follows: 60%
(poor), 75% (average), and 85% (superior). Analyzing
the results based on these criteria, all of the groups
except those with hyperopia presented with poor
competency before the training, improving to average
after training for VC. However, for 3DM, all groups
demonstrated poor competency at both experimental
times, and though the male group did not show a
significant difference after training, they increased their
average mean to just below the threshold of average
competency (74.5%). These results confirmed that
there is room for improvement in competency as a
function of education.
13
TABLE 4. Time in minutes (mean and standard deviation)
before and after training for Vita Classical (VC) and Vita
toothguide 3D Master (3DM) shade guides in Brazil and
Portugal
Time n
Before
training
After
training
VC p value
Brazil 64 12.3 6711.264.8 >0.05
Portugal 24 9.6 64.4 8.7 63.1 >0.05
pvalue <0.05 <0.05
3DM
Brazil 64 19 68.8 18.2 68.3 <0.05
Portugal 24 15.5 65.7 15.4 64.8 >0.05
pvalue <0.05 >0.05
pvalueindicates differences between means for before and after
training (rows) and for eac h country (column).
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The present study showed that the subjectivity of the
visual method might not be a clinical concern in daily
practice. The human eye can detect small differences in
color
7,34
and visualize the tooth with all its complex
geometry,
34
multilayered tissues
7
, and secondary color
parameters
2
(i.e., opalescence, fluorescence, translucency,
and metamerism). Therefore, any color-matching task
will be judged by the patient
35
and/or other observers
with consideration to this complexity. In other words,
visual assessment is paramount to the success/failure of
esthetic restorative procedures. The efficiency of the
visual color method may be improved by color education
through the development of professional color
discrimination ability. This would make the students
responsible for color selection, reproduction, and
evaluation and lead to increased capability over a
layperson observer receiving the restorative treatment.
CONCLUSION
Previous education and training in color positively
affected shade-matching ability of dental students on
shade guide pairing tests. This demonstrates the
importance of color education in dentistry and the
need for lifelong commitment to color learning.
DISCLOSURE AND ACKNOWLEDGEMENTS
The authors do not have any financial interest in the
companies whose materials are included in this article.
The authors would like to thank Dr. Maria Cristina
Figueiredo Pollmann, Professor at Faculdade de
Medicina Dent
aria, Porto University, for her significant
assistance in the experimental phase in Portugal.
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Reprint requests: Dr.Rodrigo N.Rached,Graduate Programin Dentistry,
Schoolof Life Sciences, Pontif
|cia Univ ersidade Cat
olica do P ar an
a, Ru a
Imaculada Conceic¸~
ao 1155 - P PGO, ZIP Cod e 8 0215 -901, Curitiba ^
Paran
a ^ Bra zil; Tel. : 155 (41) 988585888; email: r.rached@pucpr.br
SHADE GUIDE MATCHING Samra et al
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C2017 Wiley Periodicals, Inc. D O I 1 0 .1111/jerd.12287 9
