Art-3
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COMPARATIVE EVALUATION OF THE RELATIONSHIP
Original Articles
OF TEETH COLOR AND SOFT TISSUE COLOR OF THE FACE
IN INDIVIDUALS WITH NATURAL DENTITION
Derya Ortaç1a , Mehmet Sonugelen1b , Muharrem Erhan Çömlekoğlu1c
1Department of Prosthodontics, Faculty of Dentistry, Ege University Izmir, TR-35100 Bornova-Izmir, Turkey
a
DDS, Research Assistant; e-mail: deryortac@gmail.com; ORCIDiD: https://orcid.org/0000-0002-0169-6674
b
DDS, PhD, Professor; e-mail: mehmet.sonugelen@ege.edu.tr; ORCIDiD: https://orcid.org/0000-0002-8002-9115
c
DDS, PhD, Professor; e-mail: erhan.comlekoglu@ege.edu.tr; ORCIDiD: https://orcid.org/0000-0002-0915-5821
ABSTRACT https://doi.org/10.25241/stomaeduj.2022.9(1).art.3
Introduction The aim of this study is to make it easier for dentists to choose artificial tooth color in fully and
partially edentulous patients by evaluating the relationship between the color of the soft tissues of the face
and the color of the teeth.
Methodology The CIEL*a*b* color values of the maxillary central teeth of the volunteers participating in the
study were measured by spectrophotometer, and skin, lip and eye color were measured from facial images
containing ceramic blocks to standardize the light and color values using Adobe Photoshop software. The
Kolmogorov-Smirnow test and Spearman Rank Correlation test were used to evaluate the data.
Results It was observed that there was a higher correlation between the L* values of the teeth and the L* and
b* values of the skin.When the analysis between the color measurements taken from the lip photographs
and the teeth was examined, it was seen that there was a statistically significant positive correlation between
the L* values of the upper central teeth and the a* values of the lip.
Conclusion The results showed that the CIEL*a*b* parameters of skin color and lip color can be used in the
selection of tooth color in case of loss of natural teeth or discoloration of existing teeth.
KEYWORDS
Color Measurement; Digital Camera; Spectrophotometer; Skin Color; Tooth Color.
1. INTRODUCTION For nearly a century, dentists have used tooth color
shade guides for accurate color matching. This
There is abundant and strong scientific evidence traditional way of picking colors is oversimplified
that the appearance of a person's face and teeth has and too subjective to constitute a standart [10].
a profound effect on perception and questioning by While visual color selection with tooth color shade
others [1–3]. It is also thought that the appearance guides is the most common color matching system,
of the face and teeth have a great impact on the it is considered inconsistent and subjective as it is
development of the personality of the individual, affected by lighting, age, gender, eye fatigue [11].
getting a job, performing, believing in himself and In addition to the subject of color selection, which
being a victor. The social status of a personality and the is a very challenging process in dentistry, dentists
attractiveness of a smile are related to each other [4]. and technicians need to communicate about tooth
While in the past, functional demands were taken colors during prosthesis production procedure.
into account in oral treatments, today the focus has However, verbal communication of color differences
shifted to aesthetic dentistry with the decrease in is limited. A good color match is directly related to
caries prevalence [5,6]. Establishing an appropriate the quality of the prosthesis. The more precisely
balance between illusion and reality is the basis the tooth colors can be defined, the more accurate
of aesthetic dentistry [7]. The ultimate purpose of porcelain colors can be obtained [12–15].
aesthetic dentistry is to create beautiful smiles that To obtain the natural and harmonic restoration
are compatible with the teeth, gums, lips and face of color, it is necessary to have an objective, precise
the patient that complement each other in natural and systematic method, from the color matching
proportions [8]. One of the most important issues in procedure in dentistry to its reproduction in the
aesthetic dentistry is color selection. Therefore, every laboratory [16].
dentist should know the color matching procedures Color measuring instruments and systems such as
for aesthetics [9]. spectrophotometers, colorimeters, spectroradiome-
OPEN ACCESS This is an Open Access article under the CC BY-NC 4.0 license.
Peer-Reviewed Article
Citation: Ortaç D, Sonugelen M, Çömlekoğlu ME. Comparative evaluation of the relationship of teeth color and soft tissue color of the face in individu-
als with natural dentition. Stoma Edu J. 2022;9(1):27-37.
Received: January 02, 2022; Revised: March 17, 2022; Accepted: March 28, 2022; Published: March 30, 2022.
*Corresponding author: Dr. Derya Ortaç, DDS, Department of Prosthodontics, Faculty of Dentistry, Ege University, TR-35100 Bornova-Izmir, Turkey.
Tel.: +905436577117; Fax: 0 232 388 03 25; e-mail: deryortac@gmail.com
Copyright: © 2022 the Editorial Council for the Stomatology Edu Journal.
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ters and digital image analysis techniques have study. Permission was requested from all individuals
Original Articles
become increasingly popular, especially in dental participating in the study to take photographs, the
research. Spectrophotometers are considered reason for the study and all necessary information
among the most accurate, useful and flexible tools were explained in detail, and an informed consent
for color matching in dentistry [11,17]. It was found form was signed by all patients. Our study was
to offer a 33% increase and a more objective match approved by the Ege University Faculty of Medicine
in 93.3% of the cases [18]. Research Ethics Committee No. 20-11T/51.
Recent advances in photography and technology The exclusion criteria of the patients are listed in the
have been updated with the widespread use of the following items:
digital camera for color imaging. Digital cameras 1. If over 25 years old,
have the ability to record numerical data in an object, 2. If the maxillary central incisors are not fully erupted,
which data can then be used to produce an image 3. If there is any developmental defect in the maxillary
when viewed on a computer and transmitted over central incisors,
the internet. Images produced by a digital camera 4. If there is caries in the maxillary central incisors,
can be analyzed using suitable imaging software 5. If any restoration, root canal treatment or teeth
that allows color values to be collected from all or whitening procedures have been applied to the
part of such images. This is a much cheaper process maxillary central incisors,
than using traditional color measuring instruments 6. If extrinsic coloration is high in maxillary central
such as spectrophotometers or colorimeters [19– incisors,
21]. Digital imaging systems, on the other hand, are 7. If there is any post-surgical scarring or malformation
comparable to spectrophotometers, as they provide on the face,
additional information for color measurements and 8. If there is any skin disease and the presence of
can measure appearance properties beyond true intense tan,
color when applied correctly [22–24]. 9. If the orthodontic treatment of the individual is
Tooth color selection can become more difficult for continuing, the individuals were not included in the
clinicians when there is no tooth to be used as a
study.
reference. In these cases, the choice of tooth color
may be more subjective [6,25,26]. Patients not only
2.2. Measurement of Tooth Color with
have a healthy mouth, but they also demand a
Spectrophotometer
beautiful smile that is one with the shape of the face,
Tooth color was measured from the middle third of
eyes, hair and teeth. It is accepted that the harmony
the labial portion of both maxillary central teeth.
between tooth color and soft tissues, as well as the
Before the color selection, dental prophylaxis was
shape and arrangement of the teeth, significantly
applied to the target teeth with a mixture of pumice
affects the aesthetics of the smile [27,28].
and water in order to keep the measurement surface
There is not enough scientific data support about
the relationship between tooth color and soft clean and free from stains. Before the measurement
tissue color of the face. The existence of a possible procedure, a lip retractor was placed in the mouths of
relationship between the soft tissue color of the the individuals participating in the study.
face and the tooth color will facilitate the dentist's The tooth shade selection was made using the
selection of artificial tooth color in fully and partially Vita EasyShade Advance spectrophotometer (VITA
edentulous individuals. Since skin color and tooth Zahnfabrik GmbH, Bad Säckingen, Germany). All
color measurements are made with traditional and measurements were made under 112 cm wide Led
visual methods, more subjective data have been Fluorescent lighting with a temperature of 6500°K
obtained in the previous studies. For this reason, and a color rendering index (CRI) of 95 (Philips & Co,
in our study, tooth color was measured with a Netherlands).
spectrophotometer and the soft tissue color of It is known that the spectrophotometer device has a
the face was measured with the help of a camera fixed enhanced light source from fiber optic light at
by creating a standard environment. The aim of the measuring end, so the device can record tooth
our study is to question the existence of a possible tones in any light beam. For this reason, the lighting
correlation between tooth color and soft tissue color conditions of the environment were ignored with the
of the face in order to eliminate lack of scientific data recommendation of the manufacturer.
support in the literature. The hypothesis of this study The Vita EasyShade Advance spectrophotometer
is the presence of a correlation between tooth color device, consisting of a base and a handpiece part,
and the soft tissue color of the face. was calibrated using a ceramic calibration plate fixed
to the device before data collection. The measuring
2. METHODOLOGY handpiece part of the device was held on the ceramic
plate prepared for the calibration of the device,
2.1. Sample Description and it was held until the sound indicating that the
150 people aged 20-25, studying at Faculty of calibration was done was heard. Calibration was
Dentistry, Ege University, Izmir participated in this repeated before each tooth measurement.
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Before each measurement, an infection protection taken with a gray card, the white balance settings
Original Articles
barrier (VITA Easyshade Infection Control Shield, Vita of the ceramic block in the photos were applied to
Zahnfabrik, Bad Säckingen, Germany) was attached the other photos. A tripod was used to ensure that
to the tip of the spectrophotometer to prevent cross- images can be taken from the same distance for all
infection. The “Single Tooth Option” was selected portrait, eye and lip photos and to keep the camera
from the color selection menu. The measuring tip of stable during shooting.
the device was placed at a 90⁰ angle to the middle
third of the labial surface of the tooth. Measurements 2.4. Taking Portrait, Eye and Lip Photographs
were made in accordance with the manufacturer's After checking the standardization of the area to be
instructions and attention was paid to the correct photographed, the volunteers participating in the
positioning of the measuring tip. study were asked to gently wash their faces with warm
All measurements were made by the same water to remove dirt and cosmetics. The volunteers
investigator to ensure standardization. The average were kept at room temperature for 20 minutes after
of three consecutive measurements from the middle face washing. Volunteers sat on a stool 75 cm in
third of the labial surfaces of the targeted teeth was front of a black background; The axis of the camera
taken, and the CIE L* a* b* values and the values of lens was kept at eye level of the patient. Prior to the
the Vita 3D Master scale were recorded. All obtained photo shoot, the volunteers were asked to remove
values were recorded on previously prepared forms. photographic distractors such as hats, jewelry, and
glasses. During the photographing process, the
2.3. Standardization of the Area to Take Portrait, Eye and Frankfort Horizontal plane of the individuals was
Lip Photographs and Camera Settings positioned parallel to the ground, and the Midsagittal
In order to standardize the environment before the planes were positioned perpendicular to the ground..
photo shoot, a room in the Ege University Faculty of Before taking the photo, the auto focus feature was
Dentistry was designed to be used in this study as turned off in the camera settings, and all the photos
described below. All the windows of the room were were taken from 1.5 meters where the desired data
closed with opaque thick black covers in order to could fit into the frame in the clearest way. The first
prevent any light from leaking in and it was ensured photograph was taken with the aid of a standard gray
that it was isolated from all light sources. All portrait, reference card (Original White Balance Reference;
eye and lip photos were taken in this room. Michael Tapes Design) with known color values. The
A non-reflective black screen was used as the photograph was taken in high resolution, flash and
background for the portrait photos. A stool was placed raw data format (Fig. 1).
75 cm in front of the background so that the dark
tones in the hair of the people to be photographed
could not confused with the background. All shots
were taken with the subject to be photographed
sitting on a stool. Two speedlight overhead flashes
(Godox TT685F, Fujifilm Compatible Top Flash,
GODOX Photo Equipment Co., Ltd, Shenzhen, China)
were used as light sources, angled 45 degrees in front
of the person to be photographed. Two 10x10cm
soft boxes were used to increase the light quality, to
keep the light power standard and to provide a softer
light spread. (Godox SB1010 10x10cm Flash Softbox,
GODOX Photo Equipment Co., Ltd, Shenzhen, China) A Figure 1. Portrait, eye, lip photograph taken with Nikon D90 adjustable
randomly chosen ceramic block was fixed to a bracket camera with digital lens.
on the end of a tripod to ensure its position remained
the same across all photographs. A stationary system The camera stored the images in NEF format because
was designed by fixing the overhead flash on the the image data was not processed intact.
other end of the bracket. The ceramic block was
positioned to align the outer canthus of the subject's 2.5. Color Analysis of Photographs
right eye for each portrait and eye photograph, and 2.5.1. Skin Color Analysis from Portrait Photographs
the right commisura labiorum for all lip photographs. After taking the portrait photographs of the
External light sources and ambient conditions were volunteers participating in the study, all the images
kept constant for all individuals. were transferred to the computer. In order to ensure
All photos were taken with NIKON D90 digital lens standardization control for each portrait photograph
adjustable camera (Digital Single-Lens-Reflex, DSLR taken, the CIEL*a*b* value of the intersection point
camera) and Nikon AF-S DX Micro NIKKOR 85mm of the lines drawn from the four outer corners of the
f/3.5G ED VR lens. Before the photo shoot, ISO 200 ceramic block to the center of the rectangle in the
(International Standards Organization), aperture f5/6, first photograph taken with a gray card was measured
exposure time 1/125 sec. After the first photo was with the Adobe Photoshop program (Fig. 2).
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different regions of the face. The average of the
Original Articles
CIEL*, a* and b* values of four different reference
regions was automatically measured from a total of
approximately 10,000 separate points in the selected
regions. By using this method, it was aimed to
prevent changes in the skin such as skin spots, mild
skin inflammations and sunburn, which may cause
deviations in the measurement results.
In all photographs, the absence of clipping was
checked on the histogram showing the exposure
levels. It was also checked with histogram whether
the reference regions for the analysis of skin color
Figure 3. CIEL*a*b* value of ceramic block. remained in the overexposure or underexposure
areas. After making sure that the four reference
In order to ensure that the ceramic block, whose regions were in the areas where the exposure value of
CIEL*a*b value was measured as 94.0.0 with the the light was normal, the measurements were carried
spectrophotometer, gives this value for each out.
photograph, the measurement point was selected
using the white balance tool in the Adobe Photoshop 2.5.2. Eye Color Analysis from Eye Photographs
program. The white balance values in all the photos After taking the eye photographs of the volunteers
were adjusted according to this point located in the participating in the study, all the images were
middle of the ceramic block. transferred to the computer. In order to ensure that
In order to standardize the skin color analysis of each the light and color values of all photographs are
volunteer participating in the study, four reference the same, it was checked that the selected ceramic
regions were determined in the portrait photographs block gave the same CIEL*a*b* values for each
(Fig. 3). eye photograph. In order to standardize the eye
color analysis of each volunteer participating in the
study, the reference region to be measured in the
eye photographs was determined with the Adobe
Photoshop program.
The eye was divided into two equal hemispheres with
a horizontal axis passing through the center of the
pupil. By removing the pupil in the lower hemisphere,
the iris in this hemisphere was taken as a reference
for eye color analysis. Thus, the shadow areas formed
by the eyelash in the upper hemisphere and the light
reflections created by the ceramic block used for
standardization were eliminated (Fig. 4).
Figure 3. Reference regions for skin color measurement from portrait
photographs.
For the first region, the circular region with a width
and height of 1 mm, where the vertical descending
line from the outer canthus of the right eye and the
ala nasii-tragus line intersect on the right cheek was
taken as reference. For the second region, the circular
region with a width and height of 1 mm, where the
vertical descending line from the outer canthus of the
left eye and the ala-tragus line intersect on the left
cheek, was taken as reference. For the third region,
the circular region with a width of 5 mm above the Figure 4. Determination of the reference region to measure eye color
nasal bridge and a height of 1 mm was taken as from eye photographs with Adobe Photoshop program.
reference. For the fourth region, the circular region
with a width and height of 1 mm at the midpoint of The feature used to determine the average color
the left earlobe was taken as reference. value of a region in the Adobe Photoshop program
To determine skin color, the average CIEL*a*b* was used for the selected reference region in all eye
value of these four different regions in the portrait photographs. Thus, different pigmented areas in the
photograph of each volunteer was taken. The Adobe iris were prevented from affecting the measurement
Photoshop (Adobe Inc., San Jose, CA, USA) program alone. The CIEL*a*b* value of the region from which
was used to determine the CIEL*a*b* value of four the average color value was taken was measured
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using the Adobe Photoshop program and recorded Office Excel 2019 ®, Redmond, WA, USA) were used
Original Articles
on the pre-prepared forms. for all statistical analysis. The conformity of numerical
variables to normal distribution was examined using
2.5.3. Lip Color Analysis from Lip Photographs the Kolmogorov-Smirnov Test. The linear relationship
All the lip photographs taken were transferred to the between the color values measured on the teeth and
computer and it was checked that the ceramic block 18 independent variables from 6 different regions
used to provide light and color standardization in all on the face was examined by the Spearman rank
photographs gave the same CIEL*a*b* value for each correlation analysis. Since the normal distribution
photograph. harmony could not be obtained in the color variables
In order to analyze lip color from all lip photographs, a obtained in the study, the Friedman Test was first
circular region with a width and height of 1 mm 2 mm applied for the multi-group difference in comparing
below the philtrum was chosen as a reference (Fig. 5). the L, a and b levels between different regions.
CIE*L*a*b* values of the selected reference region Dunn's test with Bonferroni correction was used for
were measured with the Adobe Photoshop program pairwise comparisons, since the difference between
and recorded on previously prepared forms. regions was found to be significant as a result of this
test. All hypothesis checks were performed at the
0.05 significance level.
3. RESULTS
According to the Spearman Rank Correlation
made between tooth measurements and face
measurements shown in Table 1; A positive, very
weak and statistically significant correlation was
found between the b measurement of tooth number
11 and the measurement of Y3.a with a correlation
coefficient of 0.213, between the measurement of
Figure 5. Reference region for lip color measurement from lip tooth no. 21 and the measurement of Y3.b, with a
photographs. correlation coefficient of 0.187 (p<0.05). A positive,
very weak and statistically significant correlation was
2.6. Statictical Analysis found between the a measurement of tooth number
The average of 3 measurements made from the 11 and the measurement of Y3.b with a correlation
middle third of the labial surfaces of 11 and 21 was coefficient of 0.179, and the measurement of a tooth
recorded in the excel table. The average CIEL*a*b* of tooth 21 and the measurement of Y3.b with a
value of 4 regions measured on the skin from correlation coefficient of 0.187 (p<0.05). A positive,
portrait photographs was recorded as skin color, very weak and statistically significant correlation
eye color obtained from eye photographs, and lip was observed between the L measurement of
color obtained from lip photographs saved in same tooth 11 and the measurement of Y4.L, 0.203, with
excel table. IBM SPSS Statistics for Windows, Version a correlation coefficient of 0.238 between the L
25.0 package program 2017 (IBM Corp., Armonk, measurement of tooth 21 and the measurement of
NY, USA) and Microsoft Office Excel 2019 (Microsoft Y4.L (p<0.05).
Table 1. The relationship between the measurements taken from the face and the measurements taken from the teeth.
11. Teeth 21. Teeth3
L a b L a b
Rho 0.036 -0.092 -0.195 0.185 -0.003 -0.099
Y1.L
p 0.662 0.265 0.017* 0.023* 0.967 0.227
Rho 0.015 0.126 0.085 -0.044 0.084 0.038
Y1.a
p 0.853 0.124 0.303 0.593 0.304 0.641
Rho -0.142 0.098 0.084 -0.131 0.082 0.048
Y1.b
p 0.083 0.231 0.310 0.109 0.321 0.564
Rho 0.143 -0.150 -0.198 0.244 -0.091 -0.128
Y2.L
p 0.081 0.068 0.015* 0.003* 0.267 0.118
Rho -0.020 0.167 0.140 -0.095 0.114 0.070
Y2.a
p 0.812 0.041* 0.087 0.250 0.165 0.397
Rho -0.171 0.184 0.170 -0.128 0.110 0.079
Y2.b
p 0.036* 0.024* 0.037* 0.119 0.180 0.335
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Rho 0.134 -0.200 -0.278 0.272 -0.129 -0.234
p 0.103 0.014* 0.001* 0.001* 0.115 0.004*
Rho -0.095 0.185 0.213 -0.163 0.136 0.180
Y3.a
p 0.247 0.023* 0.009* 0.046* 0.097 0.028*
Rho -0.195 0.179 0.175 -0.190 0.187 0.124
Y3.b
p 0.017* 0.028* 0.033* 0.020* 0.022* 0.131
Rho 0.203 -0.057 -0.086 0.238 -0.072 -0.009
Y4.L
p 0.013* 0.491 0.297 0.003* 0.383 0.915
Rho 0.202 -0.010 0.022 0.075 -0.050 -0.021
Y4.a
p 0.013* 0.908 0.791 0.361 0.547 0.803
Rho 0.007 -0.005 -0.069 0.023 0.039 -0.060
Y4.b
p 0.930 0.953 0.405 0.776 0.634 0.463
Rho 0.135 -0.140 -0.226 0.272 -0.064 -0.134
Yt.L
p 0.101 0.087 0.005* 0.001* 0.438 0.103
Rho 0.037 0.178 0.177 -0.073 0.119 0.105
Yt.a
p 0.653 0.030* 0.030* 0.374 0.146 0.200
Rho -0.166 0.129 0.091 -0.144 0.118 0.051
Yt.b
p 0.043* 0.115 0.266 0.078 0.150 0.535
*p<0.05
According to the Spearman Rank Correlation made tooth number 11 and the L*a*b* measurements of
between tooth measurements and eye measurements the eye; no statistically significant relationship could
shown in Table 2, it was found that there were be obtained between the measurements of tooth
correlations between the L*a*b* measurements of number 21 and any eye measurement.
Table 2. The relationship between the measurements taken from the eye and the measurements taken from the teeth..
11. Teeth 21. Teeth3
L a b L a b
Rho 0.191 -0.183 -0.195 0.1445 -0.082 -0.089
G.L
p 0.020* 0.025* 0.017* 0.079 0.318 0.281
Rho 0.110 -0.12 -0.163* 0.079 -0.074 -0.059
G.a
p 0.181 0.139 0.046 0.334 0.368 0.474
Rho 0.163 -0.164 -0.174 0.100 -0.093 -0.063
G.b
p 0.046* 0.045* 0.033* 0.225 0.258 0.447
*p<0.05
According to the Spearman Rank Correlation significant correlation was found between the b
used to examine the relationships between lip measurement of tooth number 11 and the D.L
measurements and tooth measurements shown measurement with a correlation coefficient of -0.173
in Table 3, a negative, very weak and statistically (p<0.05).
Table 3. The relationship between the measurements taken from the lip and the measurements taken from the teeth.
11.Teeth 21. Teeth3
L a b L a b
Rho 0.064 -0.065 -0.173 0.181 0.071 -0.088
D.L
p 0.434 0.432 0.035* 0.026* 0.390 0.282
Rho 0.176 0.063 -0.178 0.190 -0.045 -0.129
D.a
p 0.031* 0.442 0.029* 0.020* 0.583 0.116
Rho -0.089 0.103 -0.037 -0.084 0.159 0.003
D.b
p 0.279 0.209 0.655 0.306 0.052 0.971
*p<0.05
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A positive, very weak and statistically significant In most studies in the literature, eye color was
Original Articles
correlation was found with a correlation coefficient determined by visual methods as well as skin color.
of 0.176 between the L measurement of tooth number In the study of Krasniqi et al. [37] in 2018 to determine
11 and the D.a measurement (p<0.05). A negative, a possible relationship between tooth color and skin
very weak and statistically significant correlation color and eye color, and in the study of Hassel et al.
was observed with a correlation coefficient of -0.178 [38] in 2008 evaluating the probability of predicting
between the b measurement of tooth number 11 tooth color in the elderly according to hair, eye, face
and the D.a measurement (p<0.05). A positive, very color and gender, eye color was determined visually.
weak and statistically significant relationship was categorized as brown, green, blue and dark brown.
found with a correlation coefficient of 0.181 between In the study of Lagouvardos et al. [18] investigating
the L measurement of tooth number 21 and the D.L the relationship between teeth, skin, hair and color
measurement (p<0.05). A positive, very weak and in the Greek population, eye color measurement
statistically significant correlation was obtained was made by matching the iris with the colors in the
with a correlation coefficient of 0.190 between the iris color scale suggested by Franssen et al. [39]. It is
L measurement of tooth number 21 and the D.a very difficult to standardize any visually determined
measurement (p<0.05). classification. Since these subjective methods can
vary from person to person, they cannot produce
4. DISCUSSION reproducible and reliable results.
The focus of our study is to investigate the existence
The hypothesis of this study was the presence of a of a possible relationship between L*a*b values
correlation between tooth color and the soft color of obtained from teeth by spectrophotometer and
the face. According to the results obtained from our L*a*b* values obtained from face, eye and lip
study, it was observed that there was a correlation photographs using the Adobe Photoshop program.
between skin and lip color and tooth color, but Previous studies in the literature on this subject do
there was no significant correlation between tooth not have sufficient scientific information or reports
and eye color. Therefore, the hypothesis that there that are in harmony. As a result of the findings
would be a correlation between tooth color and soft obtained in our study, it was observed that the L*
tissue color of the face was partially accepted. The value was quite close for teeth 11 and 21. L* values
differences between the results of our study and taken from the malar areas of the face are close to
similar subjects reported in the literatüre may be each other, but it was found that the L* values taken
due to the fact that the color matching procedures from the earlobe had lower L* values, unlike the
were mostly performed with the help of visual other measurement regions on the face, and the L*
methods in previous studies. Unlike other studies, a values taken from the forehead region were higher
ceramic block was used in our study to ensure that than the other measurement regions on the face. It
all photographs were in standard color and light is an expected result that the L* value is lower than
values. The fact that the color values of the ceramic the other measurement regions, since the earlobe is
block are the same for each photograph has been located in the background of the other parts of the
very supportive that we use a more standard and face, and the L* values are higher, since the forehead
objective method. region is located ahead. At the same time, a positive,
Since it is often accepted that the concept of very weak but significant relationship was obtained
aesthetics determines the character of a person in with the L* value of the teeth, the L* values obtained
modern societies, it has become a very important only from the earlobe region, and the b* values
issue [5]. Through aesthetic dentistry, the physician obtained from the forehead region of the face, so a
can make the patient's smile more beautiful while negatively, very weak but significant relationship was
giving a younger appearance [29]. Accepting the observed. It was observed that there was a positive,
smile as aesthetically compatible requires a perfect very weak but statistically significant relationship
integration of the hard and soft tissues of the face between the a* values of the teeth and the b* values
and the teeth and gums. A smile aesthetics should of the forehead region of the face, and the b* values
always include evaluation and analysis of both facial of the teeth and the a* values of the forehead region
and tooth formations [7,30]. of the face. The results obtained from our study
Today, while tooth color can be better defined with are compatible with recent studies on this subject
developing technologies, it is difficult to define skin [25,38,40–45].
tone due to the lack of a well-categorized reference In the study of Jahangiri et al. [35], it was stated
scale or guideline [31]. Most studies in the literature that there was an inversely proportional correlation
have categorized skin color visually [31–33]. In some between teeth and skin color. The methodology in
studies in the literature, skin color was classified this study was completely different from our study,
according to different cosmetic indices used to and both tooth and skin color were measured by
compare with samples such as NIVEA, LAKME or visual methods. In the study of Esan et al. [41],
L'Oreal [34–36]. both tooth and skin color were measured by visual
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Ortaç D, et al.
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methods, but no significant difference was found of the b* values of the eye was quite wide. The fact
Original Articles
between tooth color and skin color. In 2018, Lila that the L*a*b* values of the eyes are generally
et al.'s study [44], which measures tooth color concentrated in an average range can be explained
with a spectrophotometer but categorizes skin by the fact that most of the individuals participating
color according to visual perception, did not find in the study have darker eye colors. In the studies of
a relationship between tooth color and skin color. Lagouvardos et al. and Hassel et al., it was stated that
The limitations in visual color selection may have there is no linear relationship between tooth color
affected the results of studies that matched colors and eye color, which is consistent with our study
using visual methods. In our study, digital methods [38,43]. In the studies of Lila et al. and Krashniqi
were preferred when measuring both tooth and et al., it was concluded that there is a correlation
skin color and the effects of subjective factors between the upper central teeth and eye color,
were minimized. In the study of Haralur et al. [46] but there is no correlation between the color of
examining the relationship between teeth and skin the lateral and canine teeth and eye color [37,44].
color between different ethnic groups, skin color There is no consistency between the results of the
was measured with the help of digital cameras, studies, since there is no accepted standard method
similar to our study. In this study, which takes a to determine eye color and the determination of eye
few points as a reference when determining skin color in studies is based on subjective perception.
color, changes in the skin such as skin spots, mild In the statistical results obtained in our study, it
skin inflammations and sunburn may have caused was found that there were correlations between
deviations in the measurement results. In our L*a*b* measurements of tooth number 11 and
study, the mean CIEL*a*b* values of regions with a L*a*b* measurements of the eye but no statistically
width and height of 1 mm in anatomical landmarks significant correlation was found between the
to be used as a reference for color measurement measurements of tooth number 21 and any eye
were measured. Thus, by measuring the average of measurement (p>0.05). Although we did not reach
approximately 10,000 points in these regions, it is the conclusion that there is a clear linear relationship
aimed to reduce the effect of changes in the skin that between tooth color and eye color in our study, it is
will cause deviations in the measurement results. In thought that some associations found may give an
the literature, there is no scale that categorizes skin idea to dentists.
tone as a standard. While the spectrophotometer There is no study in the literature investigating
device used in our study can convert the spectral the relationship between tooth color and lip color.
reflectance measured on the tooth into CIEL*a*b* According to the findings obtained in our study, the
values, the color values measured with the help of measurement of a* values in the lip has the highest
imaging analysis used to measure skin color can also and the measurement of b* values has the lowest
be expressed in terms of CIEL*a*b*. The existence of median value compared to other variables. The fact
a standard color space in which colors are expressed that the lip color is more reddish than the color of
by both methods provides more consistent and the other soft tissues of the face explains the higher
reliable results between the regions compared. a* values and lower b values. When the analysis
According to the results obtained in our study, it between the color measurements taken from the
was observed that there was a harmony between lip photographs and the color measurements
tooth and skin color parameters. Although this fit taken from the teeth is examined, it is seen that
is considered statistically significant, it is thought to there is a statistically significant positive correlation
be useful for a rough color estimation since it ranges between the L* values of the upper central teeth
from very weak to weak. and the a* values of the lip. According to this result,
While the relationship between tooth color and skin it is understood that the teeth of individuals with
color has been the subject of research in most of more reddish lips are brighter. According to the
the studies in the literature, the number of studies results obtained from our study, there is a partial
investigating the relationship between tooth relationship between the L* values and b* values of
color and eye color is very little. In existing studies the lip and the upper central teeth.
investigating the possible relationship between The lack of literature to compare the results of our
tooth color and eye color, eye color was measured study, the limited skin color range of the individuals
by visual methods. In our study, a reference region participating in the study, the low number of
was created from all eye photographs to create a individuals with light-colored eyes, the measurement
standard in the measurement of eye color with the of tooth color only in the upper central teeth, are
help of the Adobe Photoshop program. Based on the points of the study that should be supported
the findings in our study, it was observed that the by other studies in this sense. More clinical and
L* values measured from the eye had the lowest evidence-based studies can be done to detect the
median among the L* values measured from the presence of a more precise, reliable relationship.
other soft tissues of the face, and the a* values of In further studies, with the correlations between
the eye had potential endpoints. The distribution tooth color and soft tissue color of the face, the
34 Stoma Edu J. 2022;9(1): 27-37 pISSN 2360-2406; eISSN 2502-0285
Teeth color and soft tissue color of the face
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color of the teeth can be easily determined with the 2. According to the statistical results obtained in our
Original Articles
double-stage calibration photographic technique study, a definite correlation could not be established
used in our study, using macro software that can be between tooth and eye color. It is thought that some
developed. associations between these two parameters can give
an idea to dentists.
5. CONCLUSION 3. When the analysis between the color
measurements taken from the lip photographs and
The results in the present study are summarized as the color measurements taken from the teeth was
follows. examined, it was seen that there was a statistically
1. Within the limitations of the current study, significant positive correlation between the L*
significant correlations were found between tooth values of the upper central teeth and the a* values
and skin color for CIEL*a*b* values. When the of the lip.
components of skin and tooth color are evaluated
separately, it was observed that there was a higher CONFLICT OF INTEREST
correlation between L* values of teeth and L* and The authors have no financial interest in any of the companies
b* values of skin compared to other relations. The whose products are used in this study.
results showed that CIEL*a*b* parameters of skin
color can be used in the selection of tooth color AUTHOR CONTRIBUTIONS
in case of loss of natural teeth or discoloration of DO: conceptualization, methodology, software, writing - review&
existing teeth. editing. MEÇ: investigation, visualization. MS: supervision, software.
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Derya ORTAÇ
DDS, Research Assistant
Department of Prosthodontics
Faculty of Dentistry
Ege University
TR-35100 Bornova-Izmir, Turkey
CV
Derya Ortaç graduated from Faculty of Dentistry, İzmir Kâtip Çelebi University, Izmir, Turkey in 2018 and started her PhD
programme at the Ege University, Faculty of Dentistry, Department of Prosthodontics, Bornova-Izmir, Turkey. She is still working
as a research assistant at Department of Prosthodontics, Faculty of Dentistry, Ege University. Her fields of interest are dental
materials, implant prostheses, adhesive and minimally invasive dental interventions, Temporomandibular Joint Disorders and
Occlusion and Digital Dentistry.
36 Stoma Edu J. 2022;9(1): 27-37 pISSN 2360-2406; eISSN 2502-0285
Teeth color and soft tissue color of the face
www.stomaeduj.com
Questions
Original Articles
1. Which of the following was used to determine tooth color in the study?
qa. Classic color guides;
qb. Spectrophotometer;
qc. Colorimeter;
qd. Digital camera.
2. Which of the following programs was used to determine skin, eye and lip color in the
study?
qa. Canva;
qb. Adobe Photoshop;
qc. PhotoScape;
qd. GIMP.
3. Which of the following is a conclusion that can be drawn from this study?
qa. The standardization of the color matching process with the help of digital cameras provides very
objective data in the analysis of the results;
qb. It has been shown that CIEL*a*b* parameters of skin color can be used in the selection of tooth color in
case of loss of natural teeth or discoloration of existing teeth;
qc. Within the limitations of the present study, no significant correlations were found between tooth and
skin color for CIEL*a*b* values;
qd. Spectrophotometer is not a successful device to measure tooth color.
4. What is the purpose of the study named "Evaluation of the relationship of teeth color
and soft tissue color of the face"?
qa. Choosing artificial tooth color in fully and partially edentulous patients by evaluating the relationship
between the color of the soft tissues of the face and the color of the teeth;
qb. Understanding of artificial tooth alignment in edentulous and partially edentulous cases;
qc. Comparison of the different eye, lip and skin color in the society;
qd. Examination of the relationship between lip, skin and eye color.
www.congressaio.it
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