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Correlation between three color coordinates of human teeth

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The objective was to determine whether there were significant correlations in the three color coordinates within each of two color coordinate systems, such as the Commission Internationale de l'Eclairage (CIE) L∗a∗bsystem, and the lightness, chroma, and hue angle system, of human vital teeth. The color of six maxillary and six mandibular anterior teeth was measured by the Shade Vision System. Pearson correlations between each pair of the color coordinates were determined (α= 0.01). The influence of two color coordinates on the other color coordinate was determined with a multiple regression analysis (α =0.01). Based on correlation analyses, all the color coordinate pairs showed significant correlations except for the chroma and hue angle pair. The CIE L∗was negatively correlated with the CIE a∗, b∗, and chroma, but positively correlated with the hue angle. The CIE a∗was positively correlated with the CIE b∗and chroma. Tooth color coordinates were correlated each other. Lighter teeth were less chromatic both in the CIE a∗and b∗coordinates. Therefore, it was postulated that the three color coordinates of human teeth were harmonized within certain color attribute ranges, and a lack of correlations in these coordinates might indicate external/internal discolorations and/or anomalies of teeth.
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Correlation between three color
coordinates of human teeth
Yong-Keun Lee
Downloaded From: http://biomedicaloptics.spiedigitallibrary.org/ on 05/24/2015 Terms of Use: http://spiedl.org/terms
Correlation between three color coordinates of
human teeth
Yong-Keun Lee*
Institute for Clinical Performance of Biomaterials (ICPB) and ETN Dental Clinic, 106-B101, 27 Heukseokhangang-ro, Dongjak-gu, Seoul 156-070,
Republic of Korea
Abstract. The objective was to determine whether there were significant correlations in the three color coor-
dinates within each of two color coordinate systems, such as the Commission Internationale de lEclairage (CIE)
Labsystem, and the lightness, chroma, and hue angle system, of human vital teeth. The color of six max-
illary and six mandibular anterior teeth was measured by the Shade Vision System. Pearson correlations
between each pair of the color coordinates were determined (α¼0.01). The influence of two color coordinates
on the other color coordinate was determined with a multiple regression analysis (α¼0.01). Based on corre-
lation analyses, all the color coordinate pairs showed significant correlations except for the chroma and hue
angle pair. The CIE Lwas negatively correlated with the CIE a,b, and chroma, but positively correlated
with the hue angle. The CIE awas positively correlated with the CIE band chroma. Tooth color coordinates
were correlated each other. Lighter teeth were less chromatic both in the CIE aand bcoordinates. Therefore, it
was postulated that the three color coordinates of human teeth were harmonized within certain color attribute
ranges, and a lack of correlations in these coordinates might indicate external/internal discolorations and/or
anomalies of teeth. ©2014 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.JBO.19.11.115006]
Keywords: tooth color; color coordinate; color harmony; color coordinate correlation.
Paper 140569R received Sep. 3, 2014; accepted for publication Oct. 30, 2014; published online Nov. 25, 2014.
1 Introduction
Color is a subjective sensation and as such is difficult to use in a
quantitative study.1However, varied color measuring instru-
ments such as spectrophotometer, colorimeter, spectroradio-
meter, and image analysis of digital images were used to
quantitatively express the color of teeth and orofacial tissues.2,3
Color can be described according to the Munsell color speci-
fying system in terms of Hue, Value, and Chroma.4Human teeth
occupy a range of Munsell color space approximately Hue from
8 yellow-red to 3 yellow, Value from 6/ to 8.5/ and Chroma from
/1 to /5.5Today, the most widely used quantitative color speci-
fication system is the Commision Internationale de lEclairage
(CIE) Labsystem.6In this system, the CIE Labstand
for lightness (achromatic coordinate), green-red coordinate
(negative ais green and positive ais red), and blue-yellow
coordinate (negative bis blue and positive bis yellow),
respectively. Teeth color can also be described within the cylin-
drical LCh° color space.7Lis the lightness that is defined
as the perceived brightness, ranging from black to white, and is
quantified on a scale from 0 to 100. Cis the chroma that
describes the saturation of a surface color or the degree of visual
difference from neutral grey. Hue angle (h°) forms a continuous
circular scale and is indicated in angles from 0 to 360 deg. The
cylindrical LCh° color space can be transformed into the
CIE Lab color space and vice versa.7
Tooth color is decided by a combination of the intrinsic color
resulting from the interaction of light with the tooth structure
and the presence of extrinsic stains.8,9Light scattering and
absorption within enamel and dentine give rise to the intrinsic
color of a tooth. Since enamel is relatively translucent, the
optical properties of dentine play a major role in determining
the overall tooth hue and chroma.3,10 Optical properties of
human teeth are also influenced by their external configuration.
As to the regulation of tooth shape, epithelial-mesenchymal
interactions establish the morphology of the dentine surface
upon which enamel will be deposited. Starting with the onset
of amelogenesis beneath the future cusp tips, the shape of
the enamel layer covering the crown is determined by several
growth parameters.11 The dimension, shape, and surface struc-
ture of a tooth generate light reflection patterns which influence
the overall tooth color. Knowing that the amounts of reflected
and absorbed light depend on the thickness and translucency of
these tissues, it is evident that the thicknesses of enamel and
dentine affect tooth color.12
Tooth development is determined by genetic and environ-
mental factors.13 Developmental enamel malformations can
be caused by genetic or environmental factors. A systemic con-
dition during tooth development, such as high fever, can pro-
duce a pattern of enamel defects in dentition.14 Inherited
diseases may influence the thickness of enamel or the mineral
and organic content of the enamel; therefore, they can affect
tooth color.15 Dental fluorosis processes are likely to be involved
in the genetic determination of enamel thickness and conceiv-
ably may influence tooth color.16 The process of enamel matu-
ration continues following tooth eruption, so that the erupted
tooth can change color over time.15 Adult teeth also record envi-
ronmental and traumatic events, as well as the effects of disease
and ageing.13 Human teeth are sensitive to the influences
experienced during adult life, particularly those nutritional,
*Address all correspondence to: Yong-Keun Lee, E-mail: ykleedm@gmail.com 0091-3286/2014/$25.00 © 2014 SPIE
Journal of Biomedical Optics 115006-1 November 2014 Vol. 19(11)
Journal of Biomedical Optics 19(11), 115006 (November 2014)
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metabolic, traumatic events and diseases that lead to changes in
coloration.8,17
Tooth enamel is composed of individual crystallites that are
larger and more oriented than other mineralized tissues. Mature
enamel crystallites are composed of non-stoichiometric carbon-
ated calcium hydroxyapatite.14 Tooth color is regulated by the
size of its enamel hydroxyapatite crystals.9However, the exact
genetic and/or environmental mechanisms that decide the tooth
color are not thoroughly understood at this time.
Human tooth color has been measured with varied measuring
methods.3,7,18,19 In general, these studies showed a large range in
the CIE L,aand bvalues, but consistently showed that there
was a significant contribution of the CIE bvalue or yellowness
to tooth color.3The mean values for the CIE L,a, and bof
teeth were reported as 70.7, 4.3, and 17.5, respectively, for
adults and teenagers.19 Tooth color is also a rich source of infor-
mation concerning health and genetic quality.13 Age and gender
were the most important factors associated with human tooth
color, and about half of the investigated population suffered
from some tooth discoloration and were dissatisfied with
their tooth color.19 Based on a study on the demographic, behav-
ioral, and treatment parameters that impacted tooth color and its
perception, although age contributed to objectively measured
tooth discoloration, personal satisfaction with tooth color was
age-independent.20 Dental appearance plays a key role in the
way we develop a first impression of another person. A percep-
tible change in the lightness of teeth was the strongest factor
associated with the dental attractiveness stereotype.21 On the
other hand, it was reported that the presence of yellowed colo-
ration had negative effects on ratings of attractiveness based on
an experiment on the effects of digital manipulations of teeth
color.13 This result indicated that these color-induced alterations
in ratings of attractiveness were mediated by increased/
decreased yellowing rather than whitening per se.
There have been studies that determined the correlations
between the tooth color and age/gender,22,23 color of skin,
hair and eyes,24,25 and facial features and gender.26 Several of
these results were applied in the prediction of the teeth color
from the correlated values in the studies. Color measurements
of anterior teeth showed that a tooth did not have a single uni-
form color and the middle site appeared to represent the tooth
color best.27 Although it was reported that the Munsell Hue,
Value, and Chroma of human teeth were not independent of
one another and were highly correlated with each other,5the
Munsell color attributes are basically not quantitative values
and do not have physical meanings such as the threshold values
for visual or perceptual interpretation. Since the correlations
based on the Munsell notations were not quantitative, this result
could not have quantitatively provided the degree of correlation
or harmonization of tooth color. In the present study, it was
assumed that there should be significant correlations among
the quantitative color coordinates of each tooth because the
color of each tooth is influenced by the genetic, congenital, met-
abolic, chemical, infectious, and environmental factors of each
person.17
The working hypothesis assumed in the present study was
that the three numerical color coordinates, such as the CIE
L,aand bcoordinates and the lightness (CIE L), chroma
(Cab) and hue angle (h°) coordinates, would show significant
correlations. Therefore, the influences of the color coordinates
on the other coordinates were determined using the mean values
of the same type of tooth in the same person as the raw data. The
purpose of this study was to determine whether there were sig-
nificant correlations between the numerical color coordinates of
the human teeth.
2 Material and Methods
2.1 Tooth Color Measurement
The tooth color of 47 volunteers, older than 19 years old, was
measured (number of teeth ¼564). Approval was obtained
from the institutional review board and informed consent was
obtained from each of the volunteers. Through clinical exami-
nation of oral health conditions of each volunteer, it was con-
firmed that they did not have caries, abraded lesions, or
restorations in any of the six maxillary and six mandibular ante-
rior teeth. Their periodontal conditions were in the range of fair
to good. Eight males and 39 females were included, and their
mean age was 29.5 (5.2) and 29.0 (6.8), respectively.18
The color of 12 maxillary and mandibular anterior teeth was
measured by Shade Vision System (X-rite, Grandville, MO,
USA). This system is a commercially available shade taking
device that provides an accurate colored contour mapimage
of the tooth. It is essentially a colorimeter that utilizes image-
grabbing technology. It comprises a handheld measuring device
that is used to scan the tooth surface together with a docking
station linked to a computer and associated software.28 This
device is calibrated with a reflection standard and a searchlight
illuminator is used as the light source.29 This device showed
excellent repeatability.29,30
To exclude the influence of environmental light, all the mea-
surements were performed between 5 PM to 6 PM at a dental
unit chair not receiving any direct sunlight, and one dentist
measured the color using the same measurement protocol.
The aperture head was contacted at the center of each tooth.
Measurements were repeated three times and averaged.
2.2 Color Coordinates of Teeth
Two color coordinate systems such as the CIE L,aand b
system and the lightness (CIE L), chroma (Cab), and hue
angle (h°) system were used. Chroma was calculated as Cab ¼
ða2þb2Þ12, and hue angle was calculated as h°¼
arctanðbaÞ.6
2.3 Statistical Analysis
Correlations between each pair of the three color coordinates in
each system and other correlated pairs from the CIE a,b, and
chroma were determined with a linear regression analysis
(α¼0.01). In these regressions, pairwise comparisons of the
color coordinates based on the same tooth in the same person
were made. Pearson correlation coefficient and regression equa-
tion were calculated for each pair.
Within each of the two color coordinate systems, the predict-
ability of one color coordinate from the values of two other coor-
dinates was estimated with a multiple regression analysis
(α¼0.01). For example, in the CIE L,aand bsystem,
the CIE Lcoordinate was set as a dependent variable and
the CIE aand bcoordinates were set as independent varia-
bles. These regressions were performed sequentially by switch-
ing the variables. To eliminate the impact of interrelated
independent variables, the variable which showed the lower
standardized partial correlation coefficient (β) was not included
Journal of Biomedical Optics 115006-2 November 2014 Vol. 19(11)
Lee: Correlation between three color coordinates of human teeth
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in the regression equation when the tolerance between two influ-
encing variables was lower than 0.30.31
3 Results
The mean and distribution ranges of human teeth color co-
ordinates were as follows; CIE Lrange ¼64.5 83.2 and
mean ðSD; standard deviationÞ¼74.0 ð3.4Þ,a1.6 9.8
and 5.0 (1.5), b10.4 29.0 and 19.4 (4.0), chroma ðCabÞ
10.8 29.9 and 20.1 (4.2), and hue angle ðh°Þ57.8
84.6 deg and 75.5 deg (3.1). Tooth color was in the first quad-
rant of the CIE aand bplane because the CIE aand b
values were positive; therefore, the hue angles were also in
the range of 57.8 to 84.6 deg.
Correlations between the CIE L, and aor bcoordinates
of teeth are presented in Fig. 1. Except for several isolated
points, they showed linear regression trends. Correlation
between the CIE aand bvalues is presented in Fig. 2,
which showed a high positive correlation (correlation coeffi-
cient; r¼0.66). The correlation between the lightness (CIE
L) and chroma (Fig. 3) was negative, and the correlation
between the lightness and hue angle (Fig. 3) was also observed. Correlation coefficients and regression equations between
each pair of the CIE L,aand bcoordinates, and the light-
ness, chroma, and hue angle coordinates are presented in
Table 1. When the CIE Lwas set as a dependent variable (set
as y), the correlation coefficients were in the range of 0.64 to
0.40. The CIE Lwas negatively correlated with the CIE a,b,
and chroma but positively with the hue angle. When the CIE a
was set as a dependent variable, it was positively correlated with
the CIE band chroma. When the CIE bwas set as a depen-
dent variable, it was positively correlated with the chroma
(r¼0.998). In the lightness, chroma and hue angle system,
the lightness showed a negative correlation with the chroma
and a positive correlation with the hue angle. The chroma
and hue angle showed no significant correlations.
Multiple regression results based on all the data are presented
in Table 2. The coefficient of determination (r2) means the
square of the multiple correlation coefficient and indicates
how well the data points fit a statistical model. In the CIE
L,aand bsystem, the coefficient of determination was
in the range of 0.41 to 0.57; and in the lightness, chroma,
and hue angle system, this value was in the range of 0.23 to
0.43. In this table, βmeans the standardized partial correlation
coefficient for each included variable with the dependent vari-
able when statistically significantly correlated independent var-
iables (predictors) are included. The magnitudes of coefficients
of determination for the CIE L,aand bsystem were higher
than those of the lightness, chroma, and hue angle system.
Differences in the multiple regression results for the maxil-
lary or mandibular anterior teeth are presented in Table 3. The
coefficients of determination for the maxillary teeth were in the
range of 0.22 to 0.62 and those for the mandibular teeth were
0.23 to 0.50. The orders of included variables changed in sev-
eral cases.
4 Discussion
The working hypothesis that the three numerical color coordi-
nates of human teeth would show significant correlations was
partially accepted because, in both of the color coordinate sys-
tems, the three color coordinates showed significant correlations
except for the chroma and hue angle pair. Because the chroma
refers to the intensity of the hue and the hue angle refers to
the CIE aand bratio, they indicate different aspects of
Fig. 1 Correlation between Commission Internationale de lEclairage
(CIE) Labcoordinates of human teeth.
Fig. 2 Correlation between CIE aand bvalues of human teeth.
Fig. 3 Correlation between lightness (CIE L) and chroma coordi-
nates of human teeth.
Journal of Biomedical Optics 115006-3 November 2014 Vol. 19(11)
Lee: Correlation between three color coordinates of human teeth
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the chromatic coordinates in the same plane; therefore, they did
not show significant correlation. As for the CIE aand bdis-
tribution ranges of teeth in the CIE aand bplane, these coor-
dinates were in the first quadrant, which indicates that tooth hue
is basically in the red and yellow region not far from the neutral
gray axes.
As presented in Figs. 1to 4, the color coordinate pairs
showed linear regression trends except for several isolated
points. As for the isolated points, exceptional or abnormal
color coordinates of particular teeth caused by genetic and/or
other environmental factors, measurement error, undetected dis-
coloration, or staining might have resulted in these deviated
points. As indicated in Figs. 1and 3, a lighter tooth (higher
CIE Lvalue) showed lower a(in this case, close to neutral
grey) and b(also close to neutral grey) values and accordingly
lower chroma values. When the CIE Lwas set as a dependent
variable, the correlation coefficients were in the range of 0.64
to 0.40, and it was negatively correlated with the CIE a,b,
and chroma, but positively with the hue angle (Table 1). It is not
known whether the lightness of teeth directly influenced the
chromatic color coordinates and vice versa. Further analytical
study for the theoretical and biological backgrounds of these
Table 1 Correlations between each pair of CIE L,a, and bcoordinates and lightness (CIE L), chroma (Cab ), and hue angle (h°) coordinates.
Set as x
Set as yCIE LCIE aCIE bCab h°
CIE Lr¼0.64,
y¼1.47xþ81.4a
r¼0.49,
y¼0.41xþ81.9
r¼0.51,
y¼0.42xþ82.4
r¼0.40,
y¼0.43xþ41.5
CIE ay¼0.27xþ25.3r¼0.66,
y¼0.24xþ0.36
r¼0.71,y¼0.25x0.01
CIE by¼0.58xþ62.3y¼1.84xþ10.2r¼0.998,y¼0.97x0.03
Cab y¼0.63xþ66.7y¼2.03xþ9.9y¼1.03xþ0.13 P¼0.60
h°y¼0.37xþ48.5
aPearson correlation coefficient (P<0.01).
Table 2 Multiple regression results among CIE L,aand b, and
lightness (CIE L), chroma (Cab ), and hue angle (h°) based on all
data.
yaxbMultiple r2cIncluded variables (β)d
La,b0.41 CIE a(0.56), CIE b(0.11)
aL,b0.57 CIE b(0.47), CIE L(0.41)
bL,a0.45 CIE a(0.60), CIE L(0.11)
LCab,h° 0.43 Cab (0.52), h° (0.41)
C
ab L,h° 0.32 L(0.62), h° (0.27)
h°L,Cab 0.23 L(0.553), Cab (0.31)
aThis coordinate was set as a dependent variable.
bThese coordinates were set as independent variables.
cCoefficient of determination (=square of multiple correlation coeffi-
cient). All of the significant Fvalues were lower than 0.01.
dBy the order of inclusion in the multiple linear model. Influencing var-
iable name (β=standardized correlation coefficient for each predic-
tor). All of the significant p-values were lower than 0.01.
Table 3 Differences in the multiple regression results in maxillary and mandibular teeth.
yaxb
Maxillary teeth Mandibular teeth
Multiple r2cIncluded variables (β)d Multiple r2cIncluded variables (β)d
La,b0.57 CIE a(0.53), CIE b(0.29) 0.26 CIE a(0.51)
aL,b0.62 CIE L(0.46), CIE b(0.41) 0.50 CIE b(0.51), CIE L(0.36)
bL,a0.54 CIE a(0.49), CIE L(0.30) 0.38 CIE a(0.62)
LCab,h° 0.57 Cab (0.63), h° (0.33) 0.29 h° (0.43), Cab (0.42)
Cab L,h° 0.49 L(0.75), h° (0.16) 0.23 L(0.46), h° (0.37)
h°L,Cab 0.22 L(0.61), Cab (0.25) 0.24 L(0.46), Cab (0.37)
aThis coordinate was set as a dependent variable.
bThese coordinates were set as independent variables.
cCoefficient of determination (= square of multiple correlation coefficient). All of the significant Fvalues were lower than 0.01.
dBy the order of inclusion in the multiple linear model. Influencing variable name (β= standardized correlation coefficient for each predictor). All of
the significant P-values were lower than 0.01.
Journal of Biomedical Optics 115006-4 November 2014 Vol. 19(11)
Lee: Correlation between three color coordinates of human teeth
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phenomena should be performed. The correlation coefficient
between the CIE band chroma was very high (r¼0.998).
Therefore, the chroma was mainly determined by the CIE
b, and collaterally by the CIE a(r¼0.71).
Multiple regression results based on all the data are presented
in Table 2, and the differences in the multiple regression results
between the maxillary and mandibular teeth are presented in
Table 3. The coefficients of determination for the maxillary
teeth were generally higher than those for the mandibular
teeth. Therefore, the predictability of a missing color coordinate
calculated with the other two coordinates in the maxillary teeth
would be higher than that in the mandibular teeth. Also, com-
pared with the results based on all the data (Table 2), the pre-
dictability of a missing coordinate in the maxillary teeth was
higher than all the teeth included condition except for hue
angle. As for the differences by gender, since the number of
male volunteers was limited, it seemed unreasonable to directly
compare the values. However, the trends were similar in both
male and female groups. The coefficients of determination
for males were generally higher than those for females,
which might reflect the limited numbers of isolated points in
the male group because a small number of teeth was included
(12 teeth for each of eight male volunteers =96 teeth).
The correlation coefficient between the CIE aand bwas
0.66 in the present study (P<0.01). Correlations between the
color coordinates of human teeth were already mentioned in pre-
vious studies from different viewpoints.2,5,32 In a study on the
correlations of the Munsell color attributes in natural teeth, it
was reported that three attributes were closely correlated.5
Although the correlation coefficient between Hue and Value
was reported as 0.80, direct comparison of the results with
those of the present study seemed meaningless because the
parameters used in this previous study were not truly quantita-
tive. In another study, the validity of a non-contacting spectror-
adiometer for the color determination of craniofacial structures
was assessed.2Although the authors did not perform the corre-
lation analyses for their color coordinate data of three anterior
teeth, it was presented in the graphs that the CIE aand bval-
ues showed positive correlations, the CIE Land avalues
showed negative correlations and the CIE Land bvalues
showed weak negative correlations. These results were similar
to those of the present study. Therefore, statistical analyses for
these coordinates were performed in the present study. As to the
correlation between the CIE aand b, there was a report based
on a theoretical approach.32 In the CIE color space, the chroma-
ticity coordinates are judged separately from the lightness
parameter, the latter being represented by an additional axis.6
This means that the uniform CIE Lab color system implies
strong coherences between the chromaticity data in terms of
the CIE aand bas both are located on the same plane
and should, therefore, display a strong dependency. In the
present study, in addition to the correlation between the CIE
aand bvalues, correlations between the CIE L, chroma
and hue angle were also confirmed. Heritability estimates, com-
pared with environmental effects of treatment responses to the
teeth bleaching in twins were determined.33 Whitening treat-
ment responses were highly heritable for Δband Δa, but
not for ΔL, which was essentially modulated by environmental
factors. From this study, it might be postulated that the CIE a
and b, and accordingly chroma, are highly correlated and the
CIE Lvalue is a separate parameter. As previously mentioned,
the theoretical and biological backgrounds for these phenomena
should be further studied.
The influence of variations in enamel ultrastructure on the
optical properties of teeth was investigated.9Tooth shade,
enamel chemical composition, and crystallography were
assessed. Pearson correlation analysis demonstrated that tooth
hue was associated with enamel hydroxyapatite (HA) crystal
size (r¼0.36), tooth chroma was associated with enamel
HA carbon content (r¼0.42), and tooth lightness was asso-
ciated with both enamel HA crystal size (r¼0.31) and the
degree of HA carbon content (r¼0.27). These findings are
of great relevance in dentistry since it provides a better under-
standing of tooth esthetics. Although this study partially pro-
vided biological mechanisms of tooth color determination,
the correlations among the color parameters were not discussed
in this paper. As for the theoretical approaches for tooth color
determination, measured reflectance spectra of natural enamel
and dentine specimens were in good agreement with the
KubelkaMunk theoretical values.34 The reflectance spectra
of natural enamel and dentine sections were measured and
this allowed the calculation of the KubelkaMunk scattering
and absorption parameters, which were compared with those
of the restorative materials.35
Although biological mechanisms for tooth color determina-
tion should be further studied, there have been several studies on
the influence of filler contents and other factors on the shade of
dental resin composites. These results might explain some part
of the biological or theoretical tooth color determination mech-
anisms. It was reported that the lightness of resin composites
was highly correlated with the amount of filler, scattering coef-
ficient, and refractive index (r¼0.93 0.97). But the correla-
tion coefficients between the amount of filler and chroma/hue
were moderate (r¼0.41 0.83).36 Since the scattering and
absorption characteristics influence the color of resin compo-
sites, the size and volume fraction of fillers should be controlled
for the best color reproduction, considering the refractive indices
of the filler and resin matrix.37
The limitations of the present study were (1) although the
number of investigated teeth was 564, a larger number might
have provided more trustworthy results and (2) distributions
of gender and age of the volunteers were limited. Practically,
the results of the present study can be applied to the shade
Fig. 4 Correlation between lightness (CIE L) and hue angle coordi-
nates of human teeth.
Journal of Biomedical Optics 115006-5 November 2014 Vol. 19(11)
Lee: Correlation between three color coordinates of human teeth
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guide design, prediction of missing color coordinate of teeth,
analyzing the mechanisms of tooth development/shade determi-
nation and acquired disease reflected in tooth color and the tooth
whitening effect evaluation.
5 Conclusions
Based on the results of the present study, all the color coordinate
pairs of human vital teeth showed significant correlations except
for the chroma and hue angle pair. Lighter teeth (higher L
value) showed lower a(closer to neutral grey) and b(also
closer to neutral grey) values and accordingly lower chroma.
The CIE awas positively correlated with the CIE band
chroma. Therefore, it was postulated that three color coordinates
of a tooth are harmonized within certain color attribute ranges
and a lack of correlations in these coordinates might indicate
external/internal discolorations and/or the anomaly of a tooth.
Deviations away from normal harmonized range of tooth
color coordinates might have negative effects on self-satisfac-
tion and the social attractiveness of a human.
Acknowledgments
This study received the approval of the IRB (Internal Review
Board) of Seoul National University Dental Hospital, Seoul,
Republic of Korea (CME05002). Author declared no conflict
of interest.
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Yong-Keun Lee is a doctor of dental surgery and holds a PhD
degree. He is the director of the Institute for Clinical Performance
of Biomaterials (ICPB) and ETN Dental Clinic, Seoul, Republic of
Korea.
Journal of Biomedical Optics 115006-6 November 2014 Vol. 19(11)
Lee: Correlation between three color coordinates of human teeth
Downloaded From: http://biomedicaloptics.spiedigitallibrary.org/ on 05/24/2015 Terms of Use: http://spiedl.org/terms
... The CIE-1976-L*a*b* chromaticity system in VITA Easyshade Advance4.0 software is used for analysis, and the CIE L*a*b* color notation system of CIE-Commission International e de L'eclairage (International Commission on Illumination) is the most commonly used in dental in vivo and in vitro studies and color characterization [20] [21]. In this system L*, a*, b* represent the lightness, chroma green-red coordinates (negative a is green, positive a is red) and chroma blue-yellow coordinates (negative b is blue, positive b is yellow), which is a cylindrical color space description, and tooth color can also be described in a cylindrical color space [22]. ...
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Objective To measure the difference in the crown color of the maxillary anterior teeth in the Chinese population, to study its potential regularity, and to provide a reference for the colorimetry of oral anterior teeth restoration. Method Use VITA Easyshade Advance4.0 spectrophotometer to measure the color of 1/3 of maxillary anterior crowns in different age groups, use CIE-1976-L*a*b* color system to describe the color, use Spss26.0 software Statistical analysis was performed to obtain the trend of the color change of maxillary anterior teeth. Conclusion: 1. The color of the labial crown of maxillary anterior teeth in the Chinese population is related to different age groups and tooth positions but not gender. 2. In the Chinese population, the color of the maxillary anterior teeth on the labial side gradually decreased from the central incisor to the distal end of the dental arch while the chroma gradually increased. 3. With age increase, the L* and a* values of the upper central incisors, upper lateral incisors, and upper canines gradually decrease, and the b* value gradually increases. The teeth became darker, more yellow, and redder.
... The indicator of color and saturation on the blue-yellow axis is b � (with "b+" corresponding to yellow and "b-" to blue) [43]. In this study, a decline in b � was observed for the blue axis. ...
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