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Colorimetric distribution of human attached gingiva and alveolar mucosa
CLINICAL SCIENCE
Colorimetric distribution of human attached gingiva and alveolar mucosa Hong-Keun Hyun, DDS, MSD, PhD,a Soojung Kim, DDS,b Changmin Lee, DDS,c Teo Jeon Shin, MD, PhD,d and Young-Jae Kim, DDS, MSD, PhDe The most important characABSTRACT teristic in determining facial Statement of problem. Few studies have investigated the colorimetric distribution of gingival attractiveness and esthetics color, including the posterior area and alveolar mucosa. has been reported to be overall Purpose. The purpose of this in vivo study was to investigate the distribution of colorimetric values facial harmony, including in different areas of gingiva and to determine its relationship to colorimetric findings of the tooth tooth, gingiva, and skin comand skin in a young Korean population. ponents but not limited to any Material and methods. Participants included 40 periodontally healthy adults (22 men and 18 single component.1-3 The women) 25 to 36 years of age. Commission Internationale de l’Eclairage values (CIELab: L* lightness, attached gingiva is a highly a* green-red, and b* blue-yellow) were measured using a colorimeter at a total of 23 sites for each keratinized masticatory tissue participant, including attached gingiva (AG) and alveolar mucosa (AM) in the maxillary and covered by thick stratified mandibular and incisor and molar regions, maxillary central incisor, and skin points of the squamous epithelium in which glabella, cheek, and inner upper arm. rete peg formation is evident, Results. AG showed higher L* and lower a* values than AM. AG demonstrated higher L* and lower whereas the alveolar mucosa is a* values in the maxillary region than in the mandibular region and higher b* values in the incisor composed of thin nonkeratiregion than in the molar region. AM revealed higher L* and lower a* and b* values in the incisor nized epithelium with no rete region than in the molar region. Positive significant correlations were found for L* between the skin area and AM and for b* between the skin area and AG. peg formation, and its submucosa contains loose conConclusions. The colorimetric values of AG and AM differ according to the area, possibly as a result nective tissue and fat.4,5 of differences in anatomic and histologic distribution that influence optical properties. (J Prosthet Dent 2016;-:---) Differences in the degree of keratinization and vascularization between the 2 different gingivae may contribute to metallic abutments or metal frameworks used in prosthe natural changes of color separated by the mucoginthetic procedures, including reconstructions on dental gival border.6 The width and thickness of the attached implants.16 A knowledge of normal gingival and mucosal gingiva have been reported to vary according to its color distribution in harmony with the surrounding tooth or skin components could provide a good diagnostic location.7-10 reference for abnormal periodontal conditions17 and Color changes in the gingiva can be caused by acute periodontal and gingival infections leading to hyperemia allow the development of a clinical color reference for the or the increase in blood flow,11-13 pathologic or physiogingival portion of dental prostheses.18-20 Also, inforlogic melanin pigmentation,14,15 or by the dark color of mation on the normal range of anterior tooth color in
a
Associate Professor, Department of Pediatric Dentistry, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. Postgraduate student, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. Postgraduate student, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. d Associate Professor, Department of Pediatric Dentistry, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. e Associate Professor, Department of Pediatric Dentistry, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. b c
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Table 1. Inclusion criteria
Clinical Implications The normal colorimetric values of attached gingiva and alveolar mucosa showed different distribution patterns in the maxillary and mandibular regions. Also, the colors of gingiva and skin in men were different from those in women in the same areas of measurement. Our study may help develop a clinical color reference for the normal range of healthy gingival color and gingival prostheses.
harmony with gingiva and skin may help clinicians evaluate patient requests for tooth whitening procedures or any esthetic restorative treatments and inform them that the goal of treatment may exceed the brightness naturally associated with their skin color.2,21 Previous studies of gingival color have been performed in African Americans,18 European whites,22,23 Jews,14,15,24-26 Japanese,17,27-29 Chinese,30 Taiwanese,20 Indians,31 Australian Aborigines,32 and African Americans and whites33 and in 4 different ethnic groups.34,35 These studies have shown that the color of gingiva correlates with facial skin complexion18,31 and may be associated with racial or ethnic differences.14,22,30,33 However, these studies investigated a specific area of the anterior gingiva17,20,22,23,27,30,33-35 or the gingiva surrounding the tooth, such as attached gingiva,20,23,27,30,33-35 marginal gingiva,17,27 and/or interdental gingiva.17,23,27,28 Few studies have investigated the distribution of gingival color in the posterior area and alveolar mucosa or the interrelationship between the colors of gingiva, tooth, and skin. Many previous studies also used visual measurement techniques to assess the gingival color, including observation14,15,18,24,25,31,32 and the Munsell system.23,27,33 These techniques have limitations, including the subjectivity of the observer,36 instability of the color tabs,23 and the inability to describe scientific values,37 although the Munsell system is the most popular and easiest approach.23 Other studies used a colorimeter,17 a spectrophotometer,20,29,30 or a spectroradiometer34 to produce accurate color measurements.37 Although these color measuring devices are known to be objective,38,39 they were not tested in measuring the color of the posterior gingiva and alveolar mucosa,17,20,30,34,40 and the probe diameter was reported to be too large to measure the attached gingiva without overlapping the adjacent alveolar mucosa.30 Recently, a study investigating facial skin and tooth color using an intraoral colorimeter with a probe diameter of less than 3 mm showed high reliability for the measurement of both sites.41 This hand-held colorimeter can measure the color of posterior teeth and has a flexible touch probe to
THE JOURNAL OF PROSTHETIC DENTISTRY
Young adults in good medical condition and of Korean ethnic origins Healthy alveolar mucosa, attached gingiva with a width greater than 3 mm and natural anterior teeth No bleeding on probing in central incisors and first molars Nonsmokers who responded that they had been brushing their teeth more than twice a day in the questionnaire
minimize edge loss generated by the curved tissue surface during the color measurement.42,43 Recently, the CIELab color specification system developed by the International Commission on Illumination (Commission Internationale de l’Eclairage) has been more frequently used.37,44,45 This method can quantitatively assess the chroma, hue, and value of various substrates.42 The CIELab color system consists of 3-dimensional color coordinates. The L* value represents lightness; the darkest black is indicated by 0, and the brightest white by 100. CIE values a* and b* indicate chromaticism. Positive values for CIE a* represent red, whereas negative values indicate green. Positive and negative values of CIE b* represent yellow and blue, respectively.46 The objectives of this study were to investigate the distribution of the colorimetric values of attached gingiva and alveolar mucosa in both the anterior and the posterior areas of young Korean individuals by using a colorimeter and the CIELab color system and to evaluate the relationship among these color aspects of gingiva and those measured on the tooth and skin areas. The first null hypothesis for this study was that the CIE values for the attached gingiva and alveolar mucosa measured in different sites would be similar. The second null hypothesis tested was that the measured colorimetric values would not differ by sex. The third null hypothesis was that no color difference would be found in the measurements between the right and left sides. MATERIAL AND METHODS The study participants consisted of healthy volunteers who met the inclusion and exclusion criteria described in Tables 1 and 2. The sample size was determined with a power of 80% and a significance level of .05, using maximum s=6 among the attached gingivae, calculated by a pilot study which was performed by the same examiners in the same examination room as the current study. A total of 40 participants (22 men and 18 women) 25 to 36 years of age were included in this study because 39.2 participants were required to compensate for a 10% drop rate. All participants gave informed consent to participate, and the study protocol was approved by the institutional review board of the School of Dentistry at Seoul National University (IRB no. S-D20130007).
Hyun et al
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Table 2. Exclusion criteria Central incisors or first molars with a history of endodontic or restorative treatment Any discolored central incisors or first molars from dental trauma or dental caries Any malformed teeth
3
Table 3. Measuring sites descriptions Code
Center of the labial surface of the left and right maxillary central incisors
AGUI
Attached gingiva in the maxillary incisor region, defined as 2 mm above the uppermost cervical line of the left and right maxillary central incisors
AGUM
Attached gingiva in the maxillary molar region, defined as 2 mm above the uppermost cervical line of the left and right maxillary first molars
AGLI
Attached gingiva in the mandibular incisor region, defined as 2 mm below the lowermost cervical line of the left and right mandibular central incisors
AGLM
Attached gingiva in the mandibular molar region, defined as 2 mm below the lowermost cervical line of the left and right mandibular first molars
AMUI
Alveolar mucosa in the maxillary incisor region which were 2 mm above the mucogingival line in a direction perpendicular to the uppermost cervical line of the left and right maxillary central incisors
AMUM
Alveolar mucosa in the maxillary molar region which were 2 mm above the mucogingival line in a direction perpendicular to the uppermost cervical line of the left and right maxillary first molars
AMLI
Alveolar mucosa in the mandibular incisor region which were 2 mm below the mucogingival line in a direction perpendicular to the lower most cervical line of the left and right mandibular central incisors
AMLM
Alveolar mucosa in the mandibular molar region which were 2 mm below the mucogingival line in a direction perpendicular to the lower most cervical line of the left and right mandibular first molars
History of tooth bleaching Undergoing orthodontic treatment Tooth mobility greater than 1 mm in any direction Poor periodontal conditions including inflammatory, infectious, malignant, and traumatic lesions Impaired salivary flow Abnormal hyperpigmentation or discoloration or scar tissue in the periodontium History of periodontal surgery Noticeable scar, wound, abnormal pigmentation, or tattoo on the skin of the face and forearms Noticeable skin color change caused by tanning Any form of noticeable skin disease
A total of 23 sites were defined in Table 3 and measured by 3 trained examiners (S.K., C.L., and H.K.). A periodontal probe with millimeter markings was used to measure the distance between each point and the reference point in the attached gingiva and alveolar mucosa (Fig. 1). The CIELab value for each point was measured using an intraoral colorimeter (ShadeEye NCC; Shofu Inc) equipped with a disposable flexible tip. This tip with an outside diameter of 4.0 mm at the top and 5.0 mm at the base measured an area 2.5 mm in diameter.47 The color was determined with respect to the standard illuminant D65 and the 2-degree observer function. The color difference (DE*ab) between 2 points was calculated to evaluate differences between the sexes using the following equation:44 h i1=2 DE ab = ðDLÞ2 +ðDa Þ2 +ðDb Þ2 Before tooth color was measured, dental plaque or other artifacts on the labial surface of the maxillary anterior teeth were removed using a rubber cup and pumice. The examiner placed the spot measurement device on the middle third of the mesiodistal and cervicoincisal dimension of the tooth’s labial surface. The color of the gingiva and mucosa at the target site was measured in a naturally wet condition. All participants were requested to wash their faces and remove their makeup before visiting the examination room. In order to leave no gap between the flexible tip of the touch probe and the soft tissues in the oral cavity, the skin or the labial surface of the tooth was touched gently and perpendicularly. Measurements were made 3 times for each site to obtain mean values. All measurements were made with the participant in the same chair and in the same room that received no direct sunlight and under similar ambient light conditions. The colorimeter was calibrated before each measurement. Hyun et al
Description
UCI
Glabella Skin point of the glabella, defined as the median point between the medial corners of the eyebrows Cheek
Skin point of the cheek, defined as the point intersecting the vertical line of the lateral border of the pupil and a horizontally extended line from the oral commissure
UA
Skin point of upper inner arm, defined as the point located three 3 finger widths in an upward direction, parallel to the lateral border of the upper arm above the center of the left and right cubital fossa and then two 2 finger widths in a medial direction, perpendicular to the previous line
Before measurements began, an experienced investigator (H.K.H.) trained the 3 examiners. To evaluate intraand interexaminer reliability of color measurements, every examiner measured a single point for the tooth, gingiva, and skin of a volunteer selected randomly at the 2 different times with a 1-week interval, using a block randomization procedure, and the 3 examiners measured the same points for the same person. Statistical comparisons between the left and right sides were made between each site for the tooth, attached gingiva, alveolar mucosa, and skin groups. If all parameters followed a normal distribution after checking with the Kolmogorov-Smirnov test, the values of the studied parameters in each group were compared using the paired Student t test; otherwise, the Wilcoxon signed rank test was used. The colorimetric values were compared at the measurement site of the different sexes with either the independent Student t test or MannWhitney U test depending on the test for normality by using software (SPSS v21; IBM Corp). Analysis of multiple paired data within the same participants was performed with either the parametric repeated measures ANOVA with Bonferroni correction or the nonparametric THE JOURNAL OF PROSTHETIC DENTISTRY
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Figure 1. Measurement sites used. A, Glabella, B, cheek, C, upper inner arm, and D, attached gingiva, alveolar mucosa in anterior and posterior segments, and maxillary central incisor.
Friedman test according to the normality of the distributions using software (MedCalc v15.2.2; MedCalc Software). The Pearson correlation coefficient was calculated to assess the relationship between the colorimetric variables (a=.05 for all tests). RESULTS The average age of the study population (N=40) was 28.7 ±2.7 years of age. The age range was 25 to 36 years for male participants (n=22, mean 29.0 ±2.7) and 25 to 33 years for female participants (n=18, mean 28.2 ±2.6). The intraexaminer intraclass correlation coefficients for L*, a*, and b* were 0.89 to 0.96, 0.88 to 0.97, and 0.91 to 0.95, respectively The interexaminer intraclass correlation coefficients for L*, a*, and b* were 0.89 to 0.97, 0.92 to 0.99, and 0.92 to 0.99, respectively. THE JOURNAL OF PROSTHETIC DENTISTRY
Table 4 presents comparisons of the colorimetric values of the left and right sides. No significant differences were noted among any skin points. Table 5 shows the sex-related differences in CIE value. Women showed less yellow tooth color than men. Every L* value in women was higher than that of men, except for the tooth. For most gingivae, women had less red and more yellow than men. Significant sex-related differences in every parameter on all skin points were noted. The skin of women showed a whiter, less red, and less yellow color than that of men. Color differences between men and women on the labial tooth surface, AGUM (attached gingiva in the maxillary molar region, defined as 2 mm above the uppermost cervical line of the left and right maxillary first molars), and AGLI (attached gingiva in the mandibular incisor region, defined as 2 mm below the lowermost cervical line of Hyun et al
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Table 4. Mean ±SD CIE values of different groups on right and left sides (n=40) Code
L*
a*
b*
UCI
Table 5. Mean ±SD values of different groups according to sex and mean color differences between sexes in 40 participants (22 men and 18 women) Code L* a* b* DE*ab UCI
Right
72.8 ±2.9
-0.4 ±0.6
12.5 ±2.8
Left
72.8 ±3.2
-0.4 ±0.6
12.2 ±3.1
M
72.9 ±3.5
-0.3 ±0.6
13.0 ±2.5
.580
.461
.033*
F
72.6 ±2.3
-0.5 ±0.5
11.5 ±3.3
P
.802
.097
.003*
Right
63.0 ±5.5
12.4 ±4.4
23.7 ±3.5
AGUI
Left
63.1 ±6.8
11.6 ±3.6
23.6 ±3.9
M
61.5 ±4.5
13.1 ±4.0
23.5 ±4.2
.164
.079
.714
F
64.9 ±7.3
10.7 ±3.7
23.9 ±2.9
P
<.001*
<.001*
.436
Right
62.1 ±4.9
15.3 ±4.8
21.1 ±3.4
AGUM
Left
63.0 ±5.4
13.9 ±5.2
22.1 ±4.4
M
61.4 ±4.9
14.9 ±4.9
21.6 ±4.1
.069
.010*
.005*
F
63.9 ±5.1
14.2 ±5.2
21.6 ±3.7
P
<.001*
.272
.985
Right
59.5 ±4.3
18.9 ±5.4
22.8 ±2.5
AGLI
Left
60.6 ±4.3
17.7 ±5.8
23.8 ±3.3
M
58.7 ±4.1
18.8 ±5.9
23.1 ±3.3
.002*
.006*
.001*
F
61.6 ±4.1
17.7 ±5.3
23.5 ±2.5
P
<.001*
.169
.364
Right
59.8 ±4.8
17.6 ±5.0
20.1 ±3.5
AGLM
Left
59.3 ±5.8
17.5 ±5.0
20.1 ±3.8
M
57.7 ±5.5
18.7 ±4.9
19.6 ±4.0
.758
.896
.963
F
61.9 ±4.1
16.2 ±4.7
20.7 ±3.1
P
<.001*
.001*
.004*
Right
52.9 ±5.0
27.6 ±4.4
17.1 ±3.9
AMUI
Left
54.0 ±5.0
26.4 ±5.1
16.3 ±3.8
M
51.4 ±5.0
28.5 ±4.9
16.5 ±4.0
.002*
.006*
.042*
F
56.0 ±3.9
25.2 ±3.9
17.0 ±3.6
P
<.001*
<.001*
.217
Right
50.5 ±4.4
31.7 ±5.1
22.4 ±4.4
AMUM
Left
50.4 ±5.6
31.6 ±5.7
23.1 ±5.4
M
48.0 ±4.3
33.0 ±5.6
21.3 ±5.0
.823
.810
.122
F
53.4 ±4.1
30.0 ±4.7
24.5 ±4.2
P
<.001*
<.001*
<.001*
Right
49.7 ±4.4
28.2 ±4.3
16.3 ±3.1
AMLI
Left
50.2 ±4.7
27.8 ±3.5
16.0 ±3.3
M
48.6 ±4.4
28.3 ±4.3
15.4 ±3.0
.222
.210
.146
F
51.7 ±4.1
27.7 ±3.4
17.0 ±3.3
P
<.001*
.205
<.001*
Right
48.3 ±4.0
30.8 ±3.9
20.9 ±4.4
AMLM
Left
48.2 ±4.1
31.7 ±4.2
21.0 ±3.6
M
46.6 ±3.8
31.9 ±4.0
19.9 ±4.0
.824
.025*
.852
F
50.3 ±3.4
30.4 ±4.0
22.2 ±3.6
P
<.001*
.002*
<.001*
Right
66.0 ±4.1
17.0 ±3.5
27.0 ±2.6
Glabella
Left
65.8 ±5.1
17.0 ±3.9
26.8 ±2.6
M
58.9 ±3.2
19.7 ±4.1
28.3 ±2.5
.581
.534
.215
F
64.0 ±3.2
17.2 ±3.3
26.8 ±2.5
P
<.001*
.002*
.002*
Right
67.4 ±4.4
12.4 ±4.5
24.8 ±3.6
Cheek
Left
67.3 ±4.9
12.1 ±4.3
24.9 ±3.4
M
63.7 ±4.4
18.2 ±3.7
27.7 ±2.5
.503
.112
.440
F
68.6 ±3.3
15.5 ±3.2
26.1 ±2.5
P
<.001*
<.001*
<.001*
M
65.6 ±4.4
14.0 ±4.7
25.4 ±3.6
F
69.6 ±3.8
10.1 ±3.0
24.2 ±3.2
P
<.001*
<.001*
.004*
P AGUI
P AGUM
P AGLI
P AGLM
P AMUI
P AMUM
P AMLI
P AMLM
P Cheek
P UA
P
Codes are defined in Table 3. *Asterisks indicate differences between right and left sides.
1.5
4.2
2.6
3.1
5.0
5.7
7.0
3.5
4.6
5.9
5.8
UA
the left and right mandibular central incisors) were below the previously reported 50% clinical acceptability threshold for teeth (DE*ab<2.7)48 and for human gingiva (DE*ab<3.1).16 Figure 2 demonstrates the distribution of colorimetric values according to the different measuring sites. The maxillary and anterior sites had higher L* values than the mandibular and posterior sites within the Hyun et al
5.7
*Asterisks indicate differences between sexes. Codes are defined in Table 3.
attached gingivae and alveolar mucosa. The molar site in the attached gingiva showed higher a* values than the incisal site, whereas the mandibular site in the THE JOURNAL OF PROSTHETIC DENTISTRY
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A 75
CIE L*
72.8
D
C E
65 63.0
G
G
60.0
59.6
62.5
F 65.9 H I
53.4 50.4
49.9
45 MF
AGUI M F
AGUM M F
AGLI M F
AGLM M F
AMUI M F
40
AMUM M F
AMLI M F
A B
B
CIE a*
30 20
F
10 0
12.0
D
18.3
17.6
E 14.6
31.7
C
67.4
61.2 I
55
UCI
B
27.0
28.0
J
48.2 AMLM M F
Glabella M F
Cheek M F
UA
MF
A 31.2
C 18.6
D F 17.0 12.2
G –0.4 UCI
MF
AGUI M F
AGUM M F
AGLI M F
AGLM M F
AMUI M F
AMUM M F
AMLI M F
AMLM M F
Glabella M F
Cheek M F
UA
MF
–10
CIE b*
30
C 23.7
20
E
21.6
CD
F
G H
23.3
I
22.8
20.1
J 10
D
16.7
A
A
27.6
26.9
B 24.9
20.9
16.2
12.3 UCI
MF
AGUI M F
AGUM M F
AGLI M F
AGLM M F
AMUI M F
AMUM M F
AMLI M F
AMLM M F
Glabella M F
Cheek M F
UA
MF
Measuring Sites
Figure 2. Mean CIE values of teeth, gingiva, and skin in 40 participants. Bars with the same letter did not differ significantly. See Table 3 for location codes.
alveolar mucosa showed higher a* values than the maxillary site. The maxillary site had a higher b* value than the mandibular site within the attached gingivae and the alveolar mucosa. The attached gingiva site had a higher b* value than the alveolar mucosa within the anterior group, whereas the alveolar mucosa site had a higher b* value than the attached gingiva site within the posterior group. Table 6 gives the Pearson correlation coefficients among CIE values on the different points. A significant positive correlation was found for every L* value within the skin points, the alveolar mucosa, and the attached gingivae. A significantly positive correlation for L* values between skin and alveolar mucosa was also noted, whereas there was a less significant correlation between the tooth and other tissues. The most significant correlation was observed for L* values between cheek and upper inner arm (r=.61, P<.001). In the case of CIE b*, a significant positive correlation was found within the skin points and the attached gingivae. A significantly positive correlation for b* values between the attached gingiva THE JOURNAL OF PROSTHETIC DENTISTRY
and the skin was also noted. The most significant correlation for b* values was between the cheek and glabella (r=.69; P<.001). DISCUSSION This study demonstrated that colorimetric values in the same type of gingival tissue showed differences in the different measurement areas, supporting rejection of the first null hypothesis. Facial attached gingiva is generally thicker in the maxilla than in the mandible.5 A study investigating the thickness of facial attached gingiva in periodontally healthy young male adults showed that the thickness increased in order of mandibular central incisor < mandibular second premolar < maxillary second premolar < maxillary central incisor.7 Another study using a similar ultrasonic measuring device with a similar participant group demonstrated that the thickness of buccal attached gingiva increased in the order of mandibular central incisor < maxillary first molar < maxillary central Hyun et al
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2016
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Table 6. Pearson correlation coefficient (r) matrix of teeth, gingiva, and skin colors Location Code† CIE L* UCI
UCI
AGUI
AGUM
AGLI
AGLM
AMUI
AMUM
AMLI
AMLM
Glabella
Cheek
UA
1
-.07
-.09
-.13*
-.05
.01
-.04
-.07
-.05
-.11
-.02
-.15*
1
.29**
.37**
.28**
.05
.05
.16*
.07
.25**
.22**
.08
1
.34**
.32**
.27**
.03
.14*
.14*
.17**
.14*
.12
1
.30**
.33**
.16*
.41**
.22**
.29**
.19**
.28**
1
.14*
.20**
.18**
.22**
.26**
.19**
.12
1
.54**
.55**
.47**
.45**
.17**
.28**
1
.38**
.49**
.43**
.33**
.33**
1
.43**
.39**
.20**
.26**
1
.39**
.27**
.28**
1
.52**
.47**
1
.61**
AGUI AGUM AGLI AGLM AMUI AMUM AMLI AMLM Glabella Cheek UA CIE a* UCI
1 UCI
AGUI
AGUM
AGLI
AGLM
AMUI
AMUM
AMLI
AMLM
Glabella
Cheek
UA
1
.16*
-.03
-.02
.26**
.03
.20**
-.14*
.05
.04
.18**
.26**
1
.18**
.25**
.34**
.03
.21**
.16*
.21**
.13*
.23**
.16*
1
.12
.38**
.03
-.07
-.06
.01
.09
.04
-.13*
1
.19**
.05
-.06
.27**
-.01
.12
.11
.10
1
.00
.15*
.13*
.18**
.17**
.20**
.09
1
.25**
.27**
.24**
.38**
.21**
.19**
1
.11
.40**
.23**
.28**
.32**
1
.30**
.12
.09
.04
1
.25**
.39**
.38**
1
.24**
.11
1
.63**
AGUI AGUM AGLI AGLM AMUI AMUM AMLI AMLM Glabella Cheek UA CIE b* UCI AGUI AGUM AGLI AGLM
1 UCI
AGUI
AGUM
AGLI
AGLM
AMUI
AMUM
AMLI
AMLM
Glabella
Cheek
UA
1
.09
-.01
-.05
.06
-.13*
.06
-.13*
-.00
.21**
.24**
-.01
1
.43**
.37**
.41**
.31**
.19**
.17**
.23**
.13*
.22**
.35**
1
.35**
.41**
-.03
.28**
.09
.34**
.35**
.32**
.33**
1
.30**
.07
.10
.18**
.39**
.25**
.38**
.39**
1
.09
.26**
.18**
.26**
.11
.23**
.17**
1
-.13*
.30**
.03
-.03
.11
1
.11
.42**
.02
.06
.07
1
.28**
.01
.01
.17**
1
.24**
.26**
.34**
1
.69**
.64**
1
.61**
AMUI AMUM AMLI AMLM Glabella Cheek UA
-.06
1
*Correlation is significant at a=.05. **Correlation is significant at a=.01. †Location codes are defined in Table 3.
incisor < mandibular first molar.8 The differences in thickness of keratinized tissue might have contributed to the fact that the thinner attached gingiva in the mandibular incisor region showed mandibular L* and higher a* values, whereas the thicker attached gingiva in the maxillary incisor region demonstrated higher L* and mandibular a* values in the present study. The red coloration of alveolar mucosa depends mostly on the distribution and number of blood vessels because of its extremely thin, nonkeratinized epithelium.6 A previous study investigated the vascular supply of alveolar bone in the tooth socket of dried human specimens by determining the number and size of the perforations Hyun et al
in the alveolar wall. The mean area of perforations per unit surface area in the buccal part of the alveolus of each tooth increased in the order of mandibular central incisor < maxillary central incisor < mandibular first molar < maxillary first molar, which reflected the increasing order of the blood supply to each alveolus.13 The distribution of CIE a* values of the alveolar mucosa in the present study was similar to the blood vessel distribution of the earlier study. Our study showed differences between the color of gingiva and skin in men and that in women based on the calculated color difference, whereas no significant tooth color differences were noted between the sexes. Thus, the THE JOURNAL OF PROSTHETIC DENTISTRY
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second null hypothesis was rejected for the color of gingiva and skin. The results of the present study are consistent with those of an earlier study that reported that men have yellower teeth than women but are in contrast with results from previous work in which men showed darker teeth color than women.2 An earlier study using a device measuring gingival reflectance reported that the reflectance of attached gingiva in the maxillary anterior region was not different between the sexes.22 More recent studies that evaluated the colorimetric values of attached gingiva in the maxillary central incisal area reported that L* values for women were greater than those for men, which corresponds well with our findings,20,30 although the present study further indicated the same tendency in both the anterior and posterior areas of attached gingiva and alveolar mucosa. Another investigation suggested that sex-based differences in melanin content, gingival thickness, epithelial keratinization patterns, and vascular systems in the periodontal tissue might contribute to the differences in gingival color between the sexes.20 Our study revealed that the colorimetric values of teeth, especially L*, had little correlation with those of skin and gingiva, whereas the color of gingiva was positively correlated with facial color. These findings are similar to those of earlier studies.2,18,21,31 Differences in tissue anatomic structure and pigment content between the soft and hard tissues may contribute to differences in optical properties between the 2 different kinds of tissues, possibly reflecting their unique refractive indices. In a previous report, the attached gingiva showed a light pink color, whereas the alveolar mucosa appeared red to bright red,4 which corresponds well with the results of the present study. Another study demonstrated that red coloration of the alveolar mucosa could be caused by its thin keratinization and the large distribution and number of the underlying blood vessels compared with the attached gingiva.6 The masticatory tissue including the attached gingiva has a surface keratin layer and dense collagen fiber network in the lamina propria, which, together with the effect of its irregular stippling surface, might increase light scattering and the measured lightness of the attached gingiva compared with that of the lining mucosa, including alveolar mucosa that lacks a superficial keratin layer.10 Also, the thick keratin layer in the attached gingiva stops the light from reaching the deeper vascular layers, which might decrease the influence of the underlying blood vessel on redness.10 In addition, a study investigating the microcirculation using laser Doppler velocimetry demonstrated that the alveolar mucosa showed a higher blood flow score than the attached gingiva in patients with and without gingival inflammation.12 The limitations of this study include the small sample size, no racial/ethnic comparison, and the lack of THE JOURNAL OF PROSTHETIC DENTISTRY
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evaluation of the color change in different chronological age groups. However, Korea is known to be a racially homogenous country and a study investigating the skin color of 600 Koreans with a spectrophotometer revealed that CIELab was statistically consistent for the same measurement area,45 which might reduce any possible colorimetric differences caused by ethnic variations in our study. The CIE value was not measured in the canine and premolar region because the width of the attached gingiva in both the maxillary and mandibular arch was reported to be typically narrow and less than the 3-mm probe diameter used in the present study.9 However, several differences were found between the left and right sites in the same kind of tissue, thereby rejecting the third null hypothesis, which might reflect limitations of the study such as errors when measuring small areas or irregular flexible tissue. Also, different dryness states of the oral mucosa and teeth at the time of measuring as a result of unequal air drying may affect the color measurement.19,29 The pressure of the measuring probe on the soft oral mucosa might contribute to the generation of an anemic zone, possibly influencing the measured color alterations.29 Further studies are required to investigate the characteristics of colorimetric values according to gingival thickness identified with an ultrasonic measuring device or histologic differences including vascular distribution using laser Doppler velocimetry. CONCLUSIONS Based on the findings of this clinical study, the following conclusions were made: 1. The distribution of color between attached gingiva and alveolar mucosa was different. 2. Colorimetric values measured in the same area differed according to sex. REFERENCES 1. Morley J, Eubank J. Macroesthetic elements of smile design. J Am Dent Assoc 2001;132:39-45. 2. Sabherwal RS, Gonzalez J, Naini FB. Assessing the influence of skin color and tooth shade value on perceived smile attractiveness. J Am Dent Assoc 2009;140:696-705. 3. Havens DC, McNamara JA Jr, Sigler LM, Baccetti T. The role of the posed smile in overall facial esthetics. Angle Orthod 2010;80:322-8. 4. Brand RW, Isselhard DE. Anatomy of orofacial structures-enhanced: a comprehensive approach. 7th ed. St. Louis, MO: Elsevier Health Sciences; 2014:80-1. 5. Müller HP, Eger T. Masticatory mucosa and periodontal phenotype: a review. Int J Periodontics Restorative Dent 2002;22:172-83. 6. Kleinheinz J, Büchter A, Fillies T, Joos U. Vascular basis of mucosal color. Head Face Med 2005;1:4. 7. Müller HP, Eger T. Gingival phenotypes in young male adults. J Clin Periodontol 1997;24:65-71. 8. Müller HP, Schaller N, Eger T, Heinecke A. Thickness of masticatory mucosa. J Clin Periodontol 2000;27:431-6. 9. Bowers GM. A study of the width of attached gingiva. J Periodontol 1963;34: 201-9. 10. Müller MG, Valdez TA, Georgakoudi I, Backman V, Fuentes C, Kabani S, et al. Spectroscopic detection and evaluation of morphologic and biochemical changes in early human oral carcinoma. Cancer 2003;97: 1681-92.
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11. Bergström J. Vascular reaction in plaque-induced gingivitis: a quantitative approach. J Periodontal Res 1992;27:604-8. 12. Kerdvongbundit V, Vongsavan N, Soo-Ampon S, Hasegawa A. Microcirculation and micromorphology of healthy and inflamed gingivae. Odontology 2003;91:19-25. 13. Birn H. The vascular supply of the periodontal membrane. An investigation of the number and size of perforations in the alveolar wall. J Periodontal Res 1966;1:51-68. 14. Gorsky M, Buchner A, Fundoianu-Dayan D, Aviv I. Physiologic pigmentation of the gingiva in Israeli Jews of different ethnic origin. Oral Surg Oral Med Oral Pathol 1984;58:506-9. 15. Amir E, Gorsky M, Buchner A, Sarnat H, Gat H. Physiologic pigmentation of the oral mucosa in Israeli children. Oral Surg Oral Med Oral Pathol 1991;71: 396-8. 16. Sailer I, Fehmer V, Ioannidis A, Hämmerle CH, Thoma DS. Threshold value for the perception of color changes of human gingiva. Int J Periodontics Restorative Dent 2014;34:757-62. 17. Koshi T. A study on the correlation between the Munsell values and histopathological findings in human gingiva. Nihon Shishubyo Gakkai Kaishi 1976;18:179-88. 18. Dummett CO, Sakumura JS, Barens G. The relationship of facial skin complexion to oral mucosa pigmentation and tooth color. J Prosthet Dent 1980;43:392-6. 19. Schnitzer S, Türp JC, Heydecke G. Color distribution and visual color assessment of human gingiva and mucosa: a systematic review of the literature. Int J Prosthodont 2004;17:327-32. 20. Huang JW, Chen WC, Huang TK, Fu PS, Lai PL, Tsai CF, et al. Using a spectrophotometric study of human gingival color distribution to develop a shade guide. J Dent 2011;39(suppl 3):e11-6. 21. Hassel AJ, Nitschke I, Dreyhaupt J, Wegener I, Rammelsberg P, Hassel JC. Predicting tooth color from facial features and gender: results from a white elderly cohort. J Prosthet Dent 2008;99:101-6. 22. Jones J, McFall WT Jr. A photometric study of the color of health gingiva. J Periodontol 1977;48:21-6. 23. Heydecke G, Schnitzer S, Türp JC. The color of human gingiva and mucosa: visual measurement and description of distribution. Clin Oral Investig 2005;94:257-65. 24. Steigmann S. The relationship between physiologic pigmentation of the skin and oral mucosa in Yemenite Jews. Oral Surg Oral Med Oral Pathol 1965;19: 32-8. 25. Gorsky M, Buchner A, Moskona D, Aviv I. Physiologic pigmentation of the oral mucosa in Israeli Jews of different ethnic origin. Community Dent Oral Epidemiol 1984;12:188-90. 26. Rosa DS, Aranha AC, Eduardo Cde P, Aoki A. Esthetic treatment of gingival melanin hyperpigmentation with Er:YAG laser: short-term clinical observations and patient follow-up. J Periodontol 2007;78:2018-25. 27. Ibusuki M. The color of gingiva studied by visual color matching. Part II. Kind, location, and personal difference in color of gingiva. Bull Tokyo Med Dent Univ 1975;22:281-92. 28. Ibusuki M, Asaoka K, Uchida T. Screening of inferior prosthesis by gingival color observation and visual color matching. Kokubyo Gakkai Zasshi 1978;45: 696-7. 29. Fukai K. A study of gingival color. Nihon Shishubyo Gakkai Kaishi 1988;30: 428-51. 30. Gao C, Adalet K, Liu H, Wang J. Investigation on vermilion, gingiva, and tooth color of young Uygur and Han populations in Xinjiang, China. Col Res Appl 2010;35:376-84.
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31. Ponnaiyan D, Jegadeesan V, Perumal G, Anusha A. Correlating skin color with gingival pigmentation patterns in South Indiansda cross sectional study. Oral Health Dent Manag 2014;13:132-6. 32. Brown T. Oral pigmentation in the Aborigines of Kalumburu, North-West Australia. Arch Oral Biol 1964;9:555-64. 33. Powers JM, Capp JA, Koran A. Color of gingival tissues of blacks and whites. J Dent Res 1977;56:112-6. 34. Bayindir F, Bayindir YZ, Gozalo-Diaz DJ, Wee AG. Coverage error of gingival shade guide systems in measuring color of attached anterior gingiva. J Prosthet Dent 2009;101:46-53. 35. Ito M, Marx DB, Cheng AC, Wee AG. Proposed shade guide for attached gingivada pilot study. J Prosthodont 2015;24:182-7. 36. Yap AU, Sim CP, Loh WL, Teo JH. Human-eye versus computerized color matching. Oper Dent 1999;24:358-63. 37. Brewer JD, Wee A, Seghi R. Advances in color matching. Dent Clin North Am 2004;48:341-58. 38. Jaju RA, Nagai S, Karimbux N, Da Silva JD. Evaluating tooth color matching ability of dental students. J Dent Educ 2010;74:1002-10. 39. Kröger E, Matz S, Dekiff M, Tran BL, Figgener L, Dirksen D. In vitro comparison of instrumental and visual tooth shade determination under different illuminants. J Prosthet Dent 2015;114:848-55. 40. Sala L, Carrillo-de-Albornoz A, Martín C, Bascones-Martínez A. Factors involved in the spectrophotometric measurement of soft tissue: a clinical study of interrater and intrarater reliability. J Prosthet Dent 2015;113:558-64. 41. Lagouvardos PE, Tsamali I, Papadopoulou C, Polyzois G. Tooth, skin, hair and eye color interrelationships in Greek young adults. Odontology 2013;101: 75-83. 42. Shimada K, Kakehashi Y, Matsumura H, Tanoue N. In vivo quantitative evaluation of tooth color with hand-held colorimeter and custom template. J Prosthet Dent 2004;91:389-91. 43. Hyun HK, Lee YK, Kim YJ, Kim JW, Jang KT, Kim CC, et al. Color distribution of maxillary primary incisors in Korean children. Col Res Appl 2009;35:153-8. 44. Schanda J. Colorimetry: understanding the CIE system. Hoboken, New Jersey: John Wiley & Sons; 2007. p. 25-97. 45. Han K, Choi T, Son D. Skin color of Koreans: statistical evaluation of affecting factors. Skin Res Technol 2006;12:170-7. 46. Bak SY, Kim YJ, Hyun HK. Color change of white spot lesions after resin infiltration. Col Res Appl 2014;39:506-10. 47. Tung FF, Goldstein GR, Jang S, Hittelman E. The repeatability of an intraoral dental colorimeter. J Prosthet Dent 2002;88:585-90. 48. Paravina RD, Ghinea R, Herrera LJ, Bona AD, Igiel C, Linninger M, et al. Color difference thresholds in dentistry. J Esthet Restor Dent 2015;27 Suppl 1: S1-9. Corresponding author: Dr Young-Jae Kim Department of Pediatric Dentistry School of Dentistry Seoul National University 101, Daehakno, Jongno-gu Seoul, 110-768 KOREA Email: [email protected] Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry.
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Colorimetric distribution of human attached gingiva and alveolar mucosa Hong-Keun Hyun, DDS, MSD, PhD,a Soojung Kim, DDS,b Changmin Lee, DDS,c Teo Jeon Shin, MD, PhD,d and Young-Jae Kim, DDS, MSD, PhDe The most important characABSTRACT teristic in determining facial Statement of problem. Few studies have investigated the colorimetric distribution of gingival attractiveness and esthetics color, including the posterior area and alveolar mucosa. has been reported to be overall Purpose. The purpose of this in vivo study was to investigate the distribution of colorimetric values facial harmony, including in different areas of gingiva and to determine its relationship to colorimetric findings of the tooth tooth, gingiva, and skin comand skin in a young Korean population. ponents but not limited to any Material and methods. Participants included 40 periodontally healthy adults (22 men and 18 single component.1-3 The women) 25 to 36 years of age. Commission Internationale de l’Eclairage values (CIELab: L* lightness, attached gingiva is a highly a* green-red, and b* blue-yellow) were measured using a colorimeter at a total of 23 sites for each keratinized masticatory tissue participant, including attached gingiva (AG) and alveolar mucosa (AM) in the maxillary and covered by thick stratified mandibular and incisor and molar regions, maxillary central incisor, and skin points of the squamous epithelium in which glabella, cheek, and inner upper arm. rete peg formation is evident, Results. AG showed higher L* and lower a* values than AM. AG demonstrated higher L* and lower whereas the alveolar mucosa is a* values in the maxillary region than in the mandibular region and higher b* values in the incisor composed of thin nonkeratiregion than in the molar region. AM revealed higher L* and lower a* and b* values in the incisor nized epithelium with no rete region than in the molar region. Positive significant correlations were found for L* between the skin area and AM and for b* between the skin area and AG. peg formation, and its submucosa contains loose conConclusions. The colorimetric values of AG and AM differ according to the area, possibly as a result nective tissue and fat.4,5 of differences in anatomic and histologic distribution that influence optical properties. (J Prosthet Dent 2016;-:---) Differences in the degree of keratinization and vascularization between the 2 different gingivae may contribute to metallic abutments or metal frameworks used in prosthe natural changes of color separated by the mucoginthetic procedures, including reconstructions on dental gival border.6 The width and thickness of the attached implants.16 A knowledge of normal gingival and mucosal gingiva have been reported to vary according to its color distribution in harmony with the surrounding tooth or skin components could provide a good diagnostic location.7-10 reference for abnormal periodontal conditions17 and Color changes in the gingiva can be caused by acute periodontal and gingival infections leading to hyperemia allow the development of a clinical color reference for the or the increase in blood flow,11-13 pathologic or physiogingival portion of dental prostheses.18-20 Also, inforlogic melanin pigmentation,14,15 or by the dark color of mation on the normal range of anterior tooth color in
a
Associate Professor, Department of Pediatric Dentistry, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. Postgraduate student, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. Postgraduate student, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. d Associate Professor, Department of Pediatric Dentistry, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. e Associate Professor, Department of Pediatric Dentistry, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. b c
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Table 1. Inclusion criteria
Clinical Implications The normal colorimetric values of attached gingiva and alveolar mucosa showed different distribution patterns in the maxillary and mandibular regions. Also, the colors of gingiva and skin in men were different from those in women in the same areas of measurement. Our study may help develop a clinical color reference for the normal range of healthy gingival color and gingival prostheses.
harmony with gingiva and skin may help clinicians evaluate patient requests for tooth whitening procedures or any esthetic restorative treatments and inform them that the goal of treatment may exceed the brightness naturally associated with their skin color.2,21 Previous studies of gingival color have been performed in African Americans,18 European whites,22,23 Jews,14,15,24-26 Japanese,17,27-29 Chinese,30 Taiwanese,20 Indians,31 Australian Aborigines,32 and African Americans and whites33 and in 4 different ethnic groups.34,35 These studies have shown that the color of gingiva correlates with facial skin complexion18,31 and may be associated with racial or ethnic differences.14,22,30,33 However, these studies investigated a specific area of the anterior gingiva17,20,22,23,27,30,33-35 or the gingiva surrounding the tooth, such as attached gingiva,20,23,27,30,33-35 marginal gingiva,17,27 and/or interdental gingiva.17,23,27,28 Few studies have investigated the distribution of gingival color in the posterior area and alveolar mucosa or the interrelationship between the colors of gingiva, tooth, and skin. Many previous studies also used visual measurement techniques to assess the gingival color, including observation14,15,18,24,25,31,32 and the Munsell system.23,27,33 These techniques have limitations, including the subjectivity of the observer,36 instability of the color tabs,23 and the inability to describe scientific values,37 although the Munsell system is the most popular and easiest approach.23 Other studies used a colorimeter,17 a spectrophotometer,20,29,30 or a spectroradiometer34 to produce accurate color measurements.37 Although these color measuring devices are known to be objective,38,39 they were not tested in measuring the color of the posterior gingiva and alveolar mucosa,17,20,30,34,40 and the probe diameter was reported to be too large to measure the attached gingiva without overlapping the adjacent alveolar mucosa.30 Recently, a study investigating facial skin and tooth color using an intraoral colorimeter with a probe diameter of less than 3 mm showed high reliability for the measurement of both sites.41 This hand-held colorimeter can measure the color of posterior teeth and has a flexible touch probe to
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Young adults in good medical condition and of Korean ethnic origins Healthy alveolar mucosa, attached gingiva with a width greater than 3 mm and natural anterior teeth No bleeding on probing in central incisors and first molars Nonsmokers who responded that they had been brushing their teeth more than twice a day in the questionnaire
minimize edge loss generated by the curved tissue surface during the color measurement.42,43 Recently, the CIELab color specification system developed by the International Commission on Illumination (Commission Internationale de l’Eclairage) has been more frequently used.37,44,45 This method can quantitatively assess the chroma, hue, and value of various substrates.42 The CIELab color system consists of 3-dimensional color coordinates. The L* value represents lightness; the darkest black is indicated by 0, and the brightest white by 100. CIE values a* and b* indicate chromaticism. Positive values for CIE a* represent red, whereas negative values indicate green. Positive and negative values of CIE b* represent yellow and blue, respectively.46 The objectives of this study were to investigate the distribution of the colorimetric values of attached gingiva and alveolar mucosa in both the anterior and the posterior areas of young Korean individuals by using a colorimeter and the CIELab color system and to evaluate the relationship among these color aspects of gingiva and those measured on the tooth and skin areas. The first null hypothesis for this study was that the CIE values for the attached gingiva and alveolar mucosa measured in different sites would be similar. The second null hypothesis tested was that the measured colorimetric values would not differ by sex. The third null hypothesis was that no color difference would be found in the measurements between the right and left sides. MATERIAL AND METHODS The study participants consisted of healthy volunteers who met the inclusion and exclusion criteria described in Tables 1 and 2. The sample size was determined with a power of 80% and a significance level of .05, using maximum s=6 among the attached gingivae, calculated by a pilot study which was performed by the same examiners in the same examination room as the current study. A total of 40 participants (22 men and 18 women) 25 to 36 years of age were included in this study because 39.2 participants were required to compensate for a 10% drop rate. All participants gave informed consent to participate, and the study protocol was approved by the institutional review board of the School of Dentistry at Seoul National University (IRB no. S-D20130007).
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Table 2. Exclusion criteria Central incisors or first molars with a history of endodontic or restorative treatment Any discolored central incisors or first molars from dental trauma or dental caries Any malformed teeth
3
Table 3. Measuring sites descriptions Code
Center of the labial surface of the left and right maxillary central incisors
AGUI
Attached gingiva in the maxillary incisor region, defined as 2 mm above the uppermost cervical line of the left and right maxillary central incisors
AGUM
Attached gingiva in the maxillary molar region, defined as 2 mm above the uppermost cervical line of the left and right maxillary first molars
AGLI
Attached gingiva in the mandibular incisor region, defined as 2 mm below the lowermost cervical line of the left and right mandibular central incisors
AGLM
Attached gingiva in the mandibular molar region, defined as 2 mm below the lowermost cervical line of the left and right mandibular first molars
AMUI
Alveolar mucosa in the maxillary incisor region which were 2 mm above the mucogingival line in a direction perpendicular to the uppermost cervical line of the left and right maxillary central incisors
AMUM
Alveolar mucosa in the maxillary molar region which were 2 mm above the mucogingival line in a direction perpendicular to the uppermost cervical line of the left and right maxillary first molars
AMLI
Alveolar mucosa in the mandibular incisor region which were 2 mm below the mucogingival line in a direction perpendicular to the lower most cervical line of the left and right mandibular central incisors
AMLM
Alveolar mucosa in the mandibular molar region which were 2 mm below the mucogingival line in a direction perpendicular to the lower most cervical line of the left and right mandibular first molars
History of tooth bleaching Undergoing orthodontic treatment Tooth mobility greater than 1 mm in any direction Poor periodontal conditions including inflammatory, infectious, malignant, and traumatic lesions Impaired salivary flow Abnormal hyperpigmentation or discoloration or scar tissue in the periodontium History of periodontal surgery Noticeable scar, wound, abnormal pigmentation, or tattoo on the skin of the face and forearms Noticeable skin color change caused by tanning Any form of noticeable skin disease
A total of 23 sites were defined in Table 3 and measured by 3 trained examiners (S.K., C.L., and H.K.). A periodontal probe with millimeter markings was used to measure the distance between each point and the reference point in the attached gingiva and alveolar mucosa (Fig. 1). The CIELab value for each point was measured using an intraoral colorimeter (ShadeEye NCC; Shofu Inc) equipped with a disposable flexible tip. This tip with an outside diameter of 4.0 mm at the top and 5.0 mm at the base measured an area 2.5 mm in diameter.47 The color was determined with respect to the standard illuminant D65 and the 2-degree observer function. The color difference (DE*ab) between 2 points was calculated to evaluate differences between the sexes using the following equation:44 h i1=2 DE ab = ðDLÞ2 +ðDa Þ2 +ðDb Þ2 Before tooth color was measured, dental plaque or other artifacts on the labial surface of the maxillary anterior teeth were removed using a rubber cup and pumice. The examiner placed the spot measurement device on the middle third of the mesiodistal and cervicoincisal dimension of the tooth’s labial surface. The color of the gingiva and mucosa at the target site was measured in a naturally wet condition. All participants were requested to wash their faces and remove their makeup before visiting the examination room. In order to leave no gap between the flexible tip of the touch probe and the soft tissues in the oral cavity, the skin or the labial surface of the tooth was touched gently and perpendicularly. Measurements were made 3 times for each site to obtain mean values. All measurements were made with the participant in the same chair and in the same room that received no direct sunlight and under similar ambient light conditions. The colorimeter was calibrated before each measurement. Hyun et al
Description
UCI
Glabella Skin point of the glabella, defined as the median point between the medial corners of the eyebrows Cheek
Skin point of the cheek, defined as the point intersecting the vertical line of the lateral border of the pupil and a horizontally extended line from the oral commissure
UA
Skin point of upper inner arm, defined as the point located three 3 finger widths in an upward direction, parallel to the lateral border of the upper arm above the center of the left and right cubital fossa and then two 2 finger widths in a medial direction, perpendicular to the previous line
Before measurements began, an experienced investigator (H.K.H.) trained the 3 examiners. To evaluate intraand interexaminer reliability of color measurements, every examiner measured a single point for the tooth, gingiva, and skin of a volunteer selected randomly at the 2 different times with a 1-week interval, using a block randomization procedure, and the 3 examiners measured the same points for the same person. Statistical comparisons between the left and right sides were made between each site for the tooth, attached gingiva, alveolar mucosa, and skin groups. If all parameters followed a normal distribution after checking with the Kolmogorov-Smirnov test, the values of the studied parameters in each group were compared using the paired Student t test; otherwise, the Wilcoxon signed rank test was used. The colorimetric values were compared at the measurement site of the different sexes with either the independent Student t test or MannWhitney U test depending on the test for normality by using software (SPSS v21; IBM Corp). Analysis of multiple paired data within the same participants was performed with either the parametric repeated measures ANOVA with Bonferroni correction or the nonparametric THE JOURNAL OF PROSTHETIC DENTISTRY
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Figure 1. Measurement sites used. A, Glabella, B, cheek, C, upper inner arm, and D, attached gingiva, alveolar mucosa in anterior and posterior segments, and maxillary central incisor.
Friedman test according to the normality of the distributions using software (MedCalc v15.2.2; MedCalc Software). The Pearson correlation coefficient was calculated to assess the relationship between the colorimetric variables (a=.05 for all tests). RESULTS The average age of the study population (N=40) was 28.7 ±2.7 years of age. The age range was 25 to 36 years for male participants (n=22, mean 29.0 ±2.7) and 25 to 33 years for female participants (n=18, mean 28.2 ±2.6). The intraexaminer intraclass correlation coefficients for L*, a*, and b* were 0.89 to 0.96, 0.88 to 0.97, and 0.91 to 0.95, respectively The interexaminer intraclass correlation coefficients for L*, a*, and b* were 0.89 to 0.97, 0.92 to 0.99, and 0.92 to 0.99, respectively. THE JOURNAL OF PROSTHETIC DENTISTRY
Table 4 presents comparisons of the colorimetric values of the left and right sides. No significant differences were noted among any skin points. Table 5 shows the sex-related differences in CIE value. Women showed less yellow tooth color than men. Every L* value in women was higher than that of men, except for the tooth. For most gingivae, women had less red and more yellow than men. Significant sex-related differences in every parameter on all skin points were noted. The skin of women showed a whiter, less red, and less yellow color than that of men. Color differences between men and women on the labial tooth surface, AGUM (attached gingiva in the maxillary molar region, defined as 2 mm above the uppermost cervical line of the left and right maxillary first molars), and AGLI (attached gingiva in the mandibular incisor region, defined as 2 mm below the lowermost cervical line of Hyun et al
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Table 4. Mean ±SD CIE values of different groups on right and left sides (n=40) Code
L*
a*
b*
UCI
Table 5. Mean ±SD values of different groups according to sex and mean color differences between sexes in 40 participants (22 men and 18 women) Code L* a* b* DE*ab UCI
Right
72.8 ±2.9
-0.4 ±0.6
12.5 ±2.8
Left
72.8 ±3.2
-0.4 ±0.6
12.2 ±3.1
M
72.9 ±3.5
-0.3 ±0.6
13.0 ±2.5
.580
.461
.033*
F
72.6 ±2.3
-0.5 ±0.5
11.5 ±3.3
P
.802
.097
.003*
Right
63.0 ±5.5
12.4 ±4.4
23.7 ±3.5
AGUI
Left
63.1 ±6.8
11.6 ±3.6
23.6 ±3.9
M
61.5 ±4.5
13.1 ±4.0
23.5 ±4.2
.164
.079
.714
F
64.9 ±7.3
10.7 ±3.7
23.9 ±2.9
P
<.001*
<.001*
.436
Right
62.1 ±4.9
15.3 ±4.8
21.1 ±3.4
AGUM
Left
63.0 ±5.4
13.9 ±5.2
22.1 ±4.4
M
61.4 ±4.9
14.9 ±4.9
21.6 ±4.1
.069
.010*
.005*
F
63.9 ±5.1
14.2 ±5.2
21.6 ±3.7
P
<.001*
.272
.985
Right
59.5 ±4.3
18.9 ±5.4
22.8 ±2.5
AGLI
Left
60.6 ±4.3
17.7 ±5.8
23.8 ±3.3
M
58.7 ±4.1
18.8 ±5.9
23.1 ±3.3
.002*
.006*
.001*
F
61.6 ±4.1
17.7 ±5.3
23.5 ±2.5
P
<.001*
.169
.364
Right
59.8 ±4.8
17.6 ±5.0
20.1 ±3.5
AGLM
Left
59.3 ±5.8
17.5 ±5.0
20.1 ±3.8
M
57.7 ±5.5
18.7 ±4.9
19.6 ±4.0
.758
.896
.963
F
61.9 ±4.1
16.2 ±4.7
20.7 ±3.1
P
<.001*
.001*
.004*
Right
52.9 ±5.0
27.6 ±4.4
17.1 ±3.9
AMUI
Left
54.0 ±5.0
26.4 ±5.1
16.3 ±3.8
M
51.4 ±5.0
28.5 ±4.9
16.5 ±4.0
.002*
.006*
.042*
F
56.0 ±3.9
25.2 ±3.9
17.0 ±3.6
P
<.001*
<.001*
.217
Right
50.5 ±4.4
31.7 ±5.1
22.4 ±4.4
AMUM
Left
50.4 ±5.6
31.6 ±5.7
23.1 ±5.4
M
48.0 ±4.3
33.0 ±5.6
21.3 ±5.0
.823
.810
.122
F
53.4 ±4.1
30.0 ±4.7
24.5 ±4.2
P
<.001*
<.001*
<.001*
Right
49.7 ±4.4
28.2 ±4.3
16.3 ±3.1
AMLI
Left
50.2 ±4.7
27.8 ±3.5
16.0 ±3.3
M
48.6 ±4.4
28.3 ±4.3
15.4 ±3.0
.222
.210
.146
F
51.7 ±4.1
27.7 ±3.4
17.0 ±3.3
P
<.001*
.205
<.001*
Right
48.3 ±4.0
30.8 ±3.9
20.9 ±4.4
AMLM
Left
48.2 ±4.1
31.7 ±4.2
21.0 ±3.6
M
46.6 ±3.8
31.9 ±4.0
19.9 ±4.0
.824
.025*
.852
F
50.3 ±3.4
30.4 ±4.0
22.2 ±3.6
P
<.001*
.002*
<.001*
Right
66.0 ±4.1
17.0 ±3.5
27.0 ±2.6
Glabella
Left
65.8 ±5.1
17.0 ±3.9
26.8 ±2.6
M
58.9 ±3.2
19.7 ±4.1
28.3 ±2.5
.581
.534
.215
F
64.0 ±3.2
17.2 ±3.3
26.8 ±2.5
P
<.001*
.002*
.002*
Right
67.4 ±4.4
12.4 ±4.5
24.8 ±3.6
Cheek
Left
67.3 ±4.9
12.1 ±4.3
24.9 ±3.4
M
63.7 ±4.4
18.2 ±3.7
27.7 ±2.5
.503
.112
.440
F
68.6 ±3.3
15.5 ±3.2
26.1 ±2.5
P
<.001*
<.001*
<.001*
M
65.6 ±4.4
14.0 ±4.7
25.4 ±3.6
F
69.6 ±3.8
10.1 ±3.0
24.2 ±3.2
P
<.001*
<.001*
.004*
P AGUI
P AGUM
P AGLI
P AGLM
P AMUI
P AMUM
P AMLI
P AMLM
P Cheek
P UA
P
Codes are defined in Table 3. *Asterisks indicate differences between right and left sides.
1.5
4.2
2.6
3.1
5.0
5.7
7.0
3.5
4.6
5.9
5.8
UA
the left and right mandibular central incisors) were below the previously reported 50% clinical acceptability threshold for teeth (DE*ab<2.7)48 and for human gingiva (DE*ab<3.1).16 Figure 2 demonstrates the distribution of colorimetric values according to the different measuring sites. The maxillary and anterior sites had higher L* values than the mandibular and posterior sites within the Hyun et al
5.7
*Asterisks indicate differences between sexes. Codes are defined in Table 3.
attached gingivae and alveolar mucosa. The molar site in the attached gingiva showed higher a* values than the incisal site, whereas the mandibular site in the THE JOURNAL OF PROSTHETIC DENTISTRY
6
Volume
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A 75
CIE L*
72.8
D
C E
65 63.0
G
G
60.0
59.6
62.5
F 65.9 H I
53.4 50.4
49.9
45 MF
AGUI M F
AGUM M F
AGLI M F
AGLM M F
AMUI M F
40
AMUM M F
AMLI M F
A B
B
CIE a*
30 20
F
10 0
12.0
D
18.3
17.6
E 14.6
31.7
C
67.4
61.2 I
55
UCI
B
27.0
28.0
J
48.2 AMLM M F
Glabella M F
Cheek M F
UA
MF
A 31.2
C 18.6
D F 17.0 12.2
G –0.4 UCI
MF
AGUI M F
AGUM M F
AGLI M F
AGLM M F
AMUI M F
AMUM M F
AMLI M F
AMLM M F
Glabella M F
Cheek M F
UA
MF
–10
CIE b*
30
C 23.7
20
E
21.6
CD
F
G H
23.3
I
22.8
20.1
J 10
D
16.7
A
A
27.6
26.9
B 24.9
20.9
16.2
12.3 UCI
MF
AGUI M F
AGUM M F
AGLI M F
AGLM M F
AMUI M F
AMUM M F
AMLI M F
AMLM M F
Glabella M F
Cheek M F
UA
MF
Measuring Sites
Figure 2. Mean CIE values of teeth, gingiva, and skin in 40 participants. Bars with the same letter did not differ significantly. See Table 3 for location codes.
alveolar mucosa showed higher a* values than the maxillary site. The maxillary site had a higher b* value than the mandibular site within the attached gingivae and the alveolar mucosa. The attached gingiva site had a higher b* value than the alveolar mucosa within the anterior group, whereas the alveolar mucosa site had a higher b* value than the attached gingiva site within the posterior group. Table 6 gives the Pearson correlation coefficients among CIE values on the different points. A significant positive correlation was found for every L* value within the skin points, the alveolar mucosa, and the attached gingivae. A significantly positive correlation for L* values between skin and alveolar mucosa was also noted, whereas there was a less significant correlation between the tooth and other tissues. The most significant correlation was observed for L* values between cheek and upper inner arm (r=.61, P<.001). In the case of CIE b*, a significant positive correlation was found within the skin points and the attached gingivae. A significantly positive correlation for b* values between the attached gingiva THE JOURNAL OF PROSTHETIC DENTISTRY
and the skin was also noted. The most significant correlation for b* values was between the cheek and glabella (r=.69; P<.001). DISCUSSION This study demonstrated that colorimetric values in the same type of gingival tissue showed differences in the different measurement areas, supporting rejection of the first null hypothesis. Facial attached gingiva is generally thicker in the maxilla than in the mandible.5 A study investigating the thickness of facial attached gingiva in periodontally healthy young male adults showed that the thickness increased in order of mandibular central incisor < mandibular second premolar < maxillary second premolar < maxillary central incisor.7 Another study using a similar ultrasonic measuring device with a similar participant group demonstrated that the thickness of buccal attached gingiva increased in the order of mandibular central incisor < maxillary first molar < maxillary central Hyun et al
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2016
7
Table 6. Pearson correlation coefficient (r) matrix of teeth, gingiva, and skin colors Location Code† CIE L* UCI
UCI
AGUI
AGUM
AGLI
AGLM
AMUI
AMUM
AMLI
AMLM
Glabella
Cheek
UA
1
-.07
-.09
-.13*
-.05
.01
-.04
-.07
-.05
-.11
-.02
-.15*
1
.29**
.37**
.28**
.05
.05
.16*
.07
.25**
.22**
.08
1
.34**
.32**
.27**
.03
.14*
.14*
.17**
.14*
.12
1
.30**
.33**
.16*
.41**
.22**
.29**
.19**
.28**
1
.14*
.20**
.18**
.22**
.26**
.19**
.12
1
.54**
.55**
.47**
.45**
.17**
.28**
1
.38**
.49**
.43**
.33**
.33**
1
.43**
.39**
.20**
.26**
1
.39**
.27**
.28**
1
.52**
.47**
1
.61**
AGUI AGUM AGLI AGLM AMUI AMUM AMLI AMLM Glabella Cheek UA CIE a* UCI
1 UCI
AGUI
AGUM
AGLI
AGLM
AMUI
AMUM
AMLI
AMLM
Glabella
Cheek
UA
1
.16*
-.03
-.02
.26**
.03
.20**
-.14*
.05
.04
.18**
.26**
1
.18**
.25**
.34**
.03
.21**
.16*
.21**
.13*
.23**
.16*
1
.12
.38**
.03
-.07
-.06
.01
.09
.04
-.13*
1
.19**
.05
-.06
.27**
-.01
.12
.11
.10
1
.00
.15*
.13*
.18**
.17**
.20**
.09
1
.25**
.27**
.24**
.38**
.21**
.19**
1
.11
.40**
.23**
.28**
.32**
1
.30**
.12
.09
.04
1
.25**
.39**
.38**
1
.24**
.11
1
.63**
AGUI AGUM AGLI AGLM AMUI AMUM AMLI AMLM Glabella Cheek UA CIE b* UCI AGUI AGUM AGLI AGLM
1 UCI
AGUI
AGUM
AGLI
AGLM
AMUI
AMUM
AMLI
AMLM
Glabella
Cheek
UA
1
.09
-.01
-.05
.06
-.13*
.06
-.13*
-.00
.21**
.24**
-.01
1
.43**
.37**
.41**
.31**
.19**
.17**
.23**
.13*
.22**
.35**
1
.35**
.41**
-.03
.28**
.09
.34**
.35**
.32**
.33**
1
.30**
.07
.10
.18**
.39**
.25**
.38**
.39**
1
.09
.26**
.18**
.26**
.11
.23**
.17**
1
-.13*
.30**
.03
-.03
.11
1
.11
.42**
.02
.06
.07
1
.28**
.01
.01
.17**
1
.24**
.26**
.34**
1
.69**
.64**
1
.61**
AMUI AMUM AMLI AMLM Glabella Cheek UA
-.06
1
*Correlation is significant at a=.05. **Correlation is significant at a=.01. †Location codes are defined in Table 3.
incisor < mandibular first molar.8 The differences in thickness of keratinized tissue might have contributed to the fact that the thinner attached gingiva in the mandibular incisor region showed mandibular L* and higher a* values, whereas the thicker attached gingiva in the maxillary incisor region demonstrated higher L* and mandibular a* values in the present study. The red coloration of alveolar mucosa depends mostly on the distribution and number of blood vessels because of its extremely thin, nonkeratinized epithelium.6 A previous study investigated the vascular supply of alveolar bone in the tooth socket of dried human specimens by determining the number and size of the perforations Hyun et al
in the alveolar wall. The mean area of perforations per unit surface area in the buccal part of the alveolus of each tooth increased in the order of mandibular central incisor < maxillary central incisor < mandibular first molar < maxillary first molar, which reflected the increasing order of the blood supply to each alveolus.13 The distribution of CIE a* values of the alveolar mucosa in the present study was similar to the blood vessel distribution of the earlier study. Our study showed differences between the color of gingiva and skin in men and that in women based on the calculated color difference, whereas no significant tooth color differences were noted between the sexes. Thus, the THE JOURNAL OF PROSTHETIC DENTISTRY
8
second null hypothesis was rejected for the color of gingiva and skin. The results of the present study are consistent with those of an earlier study that reported that men have yellower teeth than women but are in contrast with results from previous work in which men showed darker teeth color than women.2 An earlier study using a device measuring gingival reflectance reported that the reflectance of attached gingiva in the maxillary anterior region was not different between the sexes.22 More recent studies that evaluated the colorimetric values of attached gingiva in the maxillary central incisal area reported that L* values for women were greater than those for men, which corresponds well with our findings,20,30 although the present study further indicated the same tendency in both the anterior and posterior areas of attached gingiva and alveolar mucosa. Another investigation suggested that sex-based differences in melanin content, gingival thickness, epithelial keratinization patterns, and vascular systems in the periodontal tissue might contribute to the differences in gingival color between the sexes.20 Our study revealed that the colorimetric values of teeth, especially L*, had little correlation with those of skin and gingiva, whereas the color of gingiva was positively correlated with facial color. These findings are similar to those of earlier studies.2,18,21,31 Differences in tissue anatomic structure and pigment content between the soft and hard tissues may contribute to differences in optical properties between the 2 different kinds of tissues, possibly reflecting their unique refractive indices. In a previous report, the attached gingiva showed a light pink color, whereas the alveolar mucosa appeared red to bright red,4 which corresponds well with the results of the present study. Another study demonstrated that red coloration of the alveolar mucosa could be caused by its thin keratinization and the large distribution and number of the underlying blood vessels compared with the attached gingiva.6 The masticatory tissue including the attached gingiva has a surface keratin layer and dense collagen fiber network in the lamina propria, which, together with the effect of its irregular stippling surface, might increase light scattering and the measured lightness of the attached gingiva compared with that of the lining mucosa, including alveolar mucosa that lacks a superficial keratin layer.10 Also, the thick keratin layer in the attached gingiva stops the light from reaching the deeper vascular layers, which might decrease the influence of the underlying blood vessel on redness.10 In addition, a study investigating the microcirculation using laser Doppler velocimetry demonstrated that the alveolar mucosa showed a higher blood flow score than the attached gingiva in patients with and without gingival inflammation.12 The limitations of this study include the small sample size, no racial/ethnic comparison, and the lack of THE JOURNAL OF PROSTHETIC DENTISTRY
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evaluation of the color change in different chronological age groups. However, Korea is known to be a racially homogenous country and a study investigating the skin color of 600 Koreans with a spectrophotometer revealed that CIELab was statistically consistent for the same measurement area,45 which might reduce any possible colorimetric differences caused by ethnic variations in our study. The CIE value was not measured in the canine and premolar region because the width of the attached gingiva in both the maxillary and mandibular arch was reported to be typically narrow and less than the 3-mm probe diameter used in the present study.9 However, several differences were found between the left and right sites in the same kind of tissue, thereby rejecting the third null hypothesis, which might reflect limitations of the study such as errors when measuring small areas or irregular flexible tissue. Also, different dryness states of the oral mucosa and teeth at the time of measuring as a result of unequal air drying may affect the color measurement.19,29 The pressure of the measuring probe on the soft oral mucosa might contribute to the generation of an anemic zone, possibly influencing the measured color alterations.29 Further studies are required to investigate the characteristics of colorimetric values according to gingival thickness identified with an ultrasonic measuring device or histologic differences including vascular distribution using laser Doppler velocimetry. CONCLUSIONS Based on the findings of this clinical study, the following conclusions were made: 1. The distribution of color between attached gingiva and alveolar mucosa was different. 2. Colorimetric values measured in the same area differed according to sex. REFERENCES 1. Morley J, Eubank J. Macroesthetic elements of smile design. J Am Dent Assoc 2001;132:39-45. 2. Sabherwal RS, Gonzalez J, Naini FB. Assessing the influence of skin color and tooth shade value on perceived smile attractiveness. J Am Dent Assoc 2009;140:696-705. 3. Havens DC, McNamara JA Jr, Sigler LM, Baccetti T. The role of the posed smile in overall facial esthetics. Angle Orthod 2010;80:322-8. 4. Brand RW, Isselhard DE. Anatomy of orofacial structures-enhanced: a comprehensive approach. 7th ed. St. Louis, MO: Elsevier Health Sciences; 2014:80-1. 5. Müller HP, Eger T. Masticatory mucosa and periodontal phenotype: a review. Int J Periodontics Restorative Dent 2002;22:172-83. 6. Kleinheinz J, Büchter A, Fillies T, Joos U. Vascular basis of mucosal color. Head Face Med 2005;1:4. 7. Müller HP, Eger T. Gingival phenotypes in young male adults. J Clin Periodontol 1997;24:65-71. 8. Müller HP, Schaller N, Eger T, Heinecke A. Thickness of masticatory mucosa. J Clin Periodontol 2000;27:431-6. 9. Bowers GM. A study of the width of attached gingiva. J Periodontol 1963;34: 201-9. 10. Müller MG, Valdez TA, Georgakoudi I, Backman V, Fuentes C, Kabani S, et al. Spectroscopic detection and evaluation of morphologic and biochemical changes in early human oral carcinoma. Cancer 2003;97: 1681-92.
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31. Ponnaiyan D, Jegadeesan V, Perumal G, Anusha A. Correlating skin color with gingival pigmentation patterns in South Indiansda cross sectional study. Oral Health Dent Manag 2014;13:132-6. 32. Brown T. Oral pigmentation in the Aborigines of Kalumburu, North-West Australia. Arch Oral Biol 1964;9:555-64. 33. Powers JM, Capp JA, Koran A. Color of gingival tissues of blacks and whites. J Dent Res 1977;56:112-6. 34. Bayindir F, Bayindir YZ, Gozalo-Diaz DJ, Wee AG. Coverage error of gingival shade guide systems in measuring color of attached anterior gingiva. J Prosthet Dent 2009;101:46-53. 35. Ito M, Marx DB, Cheng AC, Wee AG. Proposed shade guide for attached gingivada pilot study. J Prosthodont 2015;24:182-7. 36. Yap AU, Sim CP, Loh WL, Teo JH. Human-eye versus computerized color matching. Oper Dent 1999;24:358-63. 37. Brewer JD, Wee A, Seghi R. Advances in color matching. Dent Clin North Am 2004;48:341-58. 38. Jaju RA, Nagai S, Karimbux N, Da Silva JD. Evaluating tooth color matching ability of dental students. J Dent Educ 2010;74:1002-10. 39. Kröger E, Matz S, Dekiff M, Tran BL, Figgener L, Dirksen D. In vitro comparison of instrumental and visual tooth shade determination under different illuminants. J Prosthet Dent 2015;114:848-55. 40. Sala L, Carrillo-de-Albornoz A, Martín C, Bascones-Martínez A. Factors involved in the spectrophotometric measurement of soft tissue: a clinical study of interrater and intrarater reliability. J Prosthet Dent 2015;113:558-64. 41. Lagouvardos PE, Tsamali I, Papadopoulou C, Polyzois G. Tooth, skin, hair and eye color interrelationships in Greek young adults. Odontology 2013;101: 75-83. 42. Shimada K, Kakehashi Y, Matsumura H, Tanoue N. In vivo quantitative evaluation of tooth color with hand-held colorimeter and custom template. J Prosthet Dent 2004;91:389-91. 43. Hyun HK, Lee YK, Kim YJ, Kim JW, Jang KT, Kim CC, et al. Color distribution of maxillary primary incisors in Korean children. Col Res Appl 2009;35:153-8. 44. Schanda J. Colorimetry: understanding the CIE system. Hoboken, New Jersey: John Wiley & Sons; 2007. p. 25-97. 45. Han K, Choi T, Son D. Skin color of Koreans: statistical evaluation of affecting factors. Skin Res Technol 2006;12:170-7. 46. Bak SY, Kim YJ, Hyun HK. Color change of white spot lesions after resin infiltration. Col Res Appl 2014;39:506-10. 47. Tung FF, Goldstein GR, Jang S, Hittelman E. The repeatability of an intraoral dental colorimeter. J Prosthet Dent 2002;88:585-90. 48. Paravina RD, Ghinea R, Herrera LJ, Bona AD, Igiel C, Linninger M, et al. Color difference thresholds in dentistry. J Esthet Restor Dent 2015;27 Suppl 1: S1-9. Corresponding author: Dr Young-Jae Kim Department of Pediatric Dentistry School of Dentistry Seoul National University 101, Daehakno, Jongno-gu Seoul, 110-768 KOREA Email: [email protected] Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry.
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