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Comparison of anteroposterior lip positions of the most-favored facial profiles of Korean and Japanese people
ORIGINAL ARTICLE
Comparison of anteroposterior lip positions of the most-favored facial profiles of Korean and Japanese people Hideki Ioi,a Takahiro Shimomura,b Shunsuke Nakata,c Akihiko Nakasima,d and Amy L. Countse Fukuoka, Japan, and Jacksonville, Fla Introduction: A consensus on the contemporary perception of beauty might have been developed between different countries because of increased worldwide access to variations in pleasing facial profiles. The objectives of this study were to determine, assess, and compare the ranges of values of the most-favored facial profiles rated by young Korean and Japanese adults. Methods: Average profiles were constructed from the profiles of 30 Japanese men and women with normal occlusions. A series of 13 profiles each was developed for men and women. In the series, the average profile was located in the center (number 7), and the lips were protruded or retruded in 1-mm increments from the average profile. Forty-six Korean dental students and 52 Japanese dental students were asked to rate the top 3 most-favored profiles. Results: Both the Korean and the Japanese dental students tended to select a slightly more retruded lip profile compared with the averages for men and women, and the tendency to prefer a more retruded lip position was evident for the women. Conclusions: These findings suggest that young Korean and Japanese adults prefer a retruded profile, even though their profiles have historically been characterized by more convex facial features. (Am J Orthod Dentofacial Orthop 2008;134:490-5)
T
reatment-planning goals for orthodontics and orthognathic surgery are based on established normal values for each ethnic group. For example, the average anteroposterior lip position in Japanese adults is relatively more protrusive than that of white people. The same observation in Korean adults has been reported in previous studies.1,2 Regarding hardand soft-tissue measurements, both Japanese and Koreans have a more retruded chin position, protruding mandibular incisors, and more protruded lip positions compared with white norms.1-3 It is important to consider the perceptions of nonorthodontists in determining the most pleasant profile because the goals of orthodontic treatment are not only to achieve a functional occlusion, but also to create an esthetic profile.4 a
Lecturer, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. Resident, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. c Associate professor, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. d Professor, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. e Professor, Dental School of Orthodontics, Jacksonville University, Jacksonville, Fla. Reprint requests to: Hideki Ioi, Department of Orthodontics, Faculty of Dentistry, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; e-mail, [email protected]. Submitted, July 2006; revised and accepted, September 2006. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.09.070 b
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We previously reported on the Japanese perception of the most-favored profiles rated by orthodontists and dental students.5 However, no reports have attempted to compare and quantify soft-tissue lip positions of the most-favored profiles between Korean and Japanese subjects. Korean and Japanese people originated from the same racial group and have similar cultural backgrounds. Moreover, young adults experience great exposure to mass media—television, movies, the Internet, and travel. The perception of a pleasing facial profile can differ between 2 countries or might be changing to a more internationally pleasing one. In light of these facts, we aimed to determine the most pleasing profiles for young Korean and Japanese adults. Facial silhouettes were chosen for rating the profiles, rather than facial photos, to avoid subjective considerations.6,7 The purposes of this study were to determine, assess, and compare the range of soft-tissue anteroposterior lip position of the top 3 most-favored profiles rated by young Korean and Japanese adults from a series of varying lip positions in facial silhouettes. MATERIAL AND METHODS
Average Japanese silhouettes were constructed from 30 cephalometric radiographs (15 men, 15 women) of Japanese adults aged 22 to 26 years. Inclusion criteria for this study were ANB angle between 2° and 5°, normal occlusion with minor or no crowding, all teeth present
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RESULTS
Fig 1. Soft tissue cephalometric reference points and analyses: 1, upper lip protrusion (Ls to Sn-Pg=); 2, lower lip protrusion (Li to Sn-Pg=); 3, upper lip to E-line (Ls to E-line); 4, lower lip to E-line (Li to E-line); 5, nasolabial angle (Cm-Sn-Ls); 6, Z-angle (chin/lip line to FH plane).
except third molars, no previous orthodontic treatment, and no prosthetic replacement of teeth. The details of constructing the average profile were given in a previous article.5 Soft-tissue reference points and angles are shown in Figure 1. We obtained 4 linear and 2 angular measurements for the soft-tissue analysis. A series of 13 profiles was developed and arranged for men and women on the paper, respectively (Fig 2). In the series, the average profile (number 7) was in the center position. The lips were protruded or retruded in 1-mm increments from the average profile, and the lip positions were changed parallel to the Frankfort horizontal plane. Profile number 1 was the most retrusive, and number 13 was the most protrusive. The profile raters were 46 Korean dental students (32 men, 14 women; age, 24.2 ⫾ 2.0 years) from Kyungpook National University in Daegu and Pusan National University in Pusan, Korea, and 52 Japanese dental students (35 men 17 women; age, 24.5 ⫾ 2.1 years) from Kyushu University in Fukuoka, Japan. They were asked to choose the top 3 most-favored profiles. Statistical analysis
The Fisher exact probability tests were used to compare the differences in the scores between the top 3 most-favored profiles and the other profiles, and to compare the distribution of the 3 most-favored profiles between the Koreans and Japanese. Probability of less than .05 was considered statistically significant.
For the Korean dental students, the top 3 male profiles were numbers 5, 6, and 4 (Fig 3), and the most-favored female profiles were numbers 4, 3, and 5 (Fig 4). The scores for the top 3 male profiles were significantly greater than for the other profiles (P ⬍0.05). On the other hand, the scores for the top 3 female profiles were significantly greater than the other profiles (P ⬍0.05), except between numbers 2 and 3, numbers 2 and 5, and numbers 5 and 6. For the Japanese dental students, the 3 most-favored male profiles were numbers 5, 6, and 4 (Fig 3), and the 3 most-favored female profiles were numbers 3, 4, and 5 (Fig 4). The scores in the top 3 male profiles were significantly greater than for the other profiles (P ⬍0.05), except between numbers 4 and 7, and numbers 6 and 7. On the other hand, the scores for the top 3 female profiles were significantly greater than for the other profiles (P ⬍0.05), except between numbers 2 and 5, numbers 3 and 6, numbers 4 and 6, and numbers 5 and 6. There was no significant difference in the distribution of the top 3 most-favored profiles between the Koreans and the Japanese. From these most-favored profiles, rated by Korean and Japanese dental students, the ranges of the following soft-tissue measurements were determined: lip protrusion to Sn-Pg= or the esthetic line, nasolabial angle associated with the most-favored profiles, and Z-angle for men and women (Table). For men, both the Korean and Japanese dental students chose the following ranges: the mostfavored lip protrusion values relative to Sn-Pg= were 3.4 to 5.4 mm for the upper lip and 2.7 to 4.7 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺5.5 to ⫺3.5 mm for the upper lip and ⫺2.0 to 0 mm for the lower lip. The range of mostfavored nasolabial angle values associated with the mostfavored profiles was 94° to 96°. The range of mostfavored Z-angle values was 72° to 75°. For women, both the Korean and Japanese dental students chose the following ranges: the ranges of the most-favored lip protrusion values relative to Sn-Pg= were 2.5 to 4.5 mm for the upper lip and 2.4 to 4.4 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺4.5 to ⫺2.5 mm for the upper lip and ⫺1.5 to 0.5 mm for the lower lip. The range of nasolabial angle values associated with the most-favored profiles was 100° to 102°. The most-favored Z-angle range was 73° to 75°. DISCUSSION
In this study, Japanese samples were used for constructing the average facial profiles. Although Korean and
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Fig 2. Series of 13 profiles rated by Korean and Japanese dental students for men (upper row) and women (lower row).
Japanese people are the same racial group, the normal values of cephalometric hard- and soft-tissue measurements can differ between them. Because we confirmed that the normal values of lip protrusion were similar (Korean men and women, 0.7 ⫾ 2.7 and 0.2 ⫾ 1.7 mm, respectively; Japanese men and women, 0.3 ⫾ 2.6 and 0.9 ⫾ 1.9 mm, respectively),1,3 we decided to use the same series of facial profiles in this study and made the number 7 profile the average in both groups. Moreover, we considered that the same facial profiles could shed light on the differences of facial preference between the 2 countries. The objectives of orthodontic treatment are to achieve facial balance, through stabilization of the dentition, and to produce pleasing facial and dental esthetics.8 Therefore, it is important to identify and define the characteristics of a pleasing face, as well as those of a functioning occlusion. Our predecessors, including philosophers and artists, attempted to define beauty. However, it was difficult to determine the standards of beauty, because of tremendous variations among people in different racial groups.8 To date, no studies have attempted to compare and quantify soft-tissue lip positions of the most-favored profiles between Korean and Japanese subjects. Because the perception of beauty might differ between the 2 countries, it
appears reasonable to evaluate the most pleasing faces of Koreans and Japanese. Worldwide communications through the media, such as the Internet, television, movies, and magazines, have expanded in recent years. People who are potential candidates for orthodontic treatment are likely to be profoundly influenced by these media. Our hypothesis was that there might be consensus on the contemporary perception of beauty between different countries because of increased worldwide access to variations in pleasing facial profiles. Our objectives were to determine, assess, and compare the values of the mostfavored facial profiles rated by Korean and Japanese dental students. The Korean dental students rated the most-favored profiles as slightly more retruded compared with the average for both men and women. If the raters in this study chose the average profile as the most-favored one, they would have selected number 7. Number 5 was considered the most favored for men and number 4 for women. The tendency was to prefer an even more slightly retruded lip position than the average lip position for women. On the other hand, the Japanese dental students regarded number 5 as the best profile for men and number 3 or 4 as the
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Fig 3. Distribution of the most-favored male profiles rated by the Korean and Japanese dental students.
Fig 4. Distribution of the most-favored female profiles rated by the Korean and Japanese dental students.
best for women. Young Korean and Japanese adults have similar perceptions of the most-favored facial profiles: they preferred slightly more retruded lip positions compared with the average for both men and women, and this tendency was more evident for the women. They preferred a slightly retruded lip position, even though their profiles were characterized by convex features.1,2,9 Soh et al10 reported that normal and bimaxillary retrusive Chinese male and female profiles were judged to be highly attractive by orthodontists and oral surgeons. These results might imply that a perception of beauty could have been established across the borders of Asian countries. For men and women, the Korean and Japanese
dental students preferred the same ranges of favored lip protrusion relative to Ls to Sn-Pg=, Li to Sn-Pg=, Ls to E-line, Li to E-line, nasolabial angle, and Z-angle, respectively. Park et al1 and Miyajima et al3 reported that normal Korean lip protrusions to the esthetic line were 0.7 mm for men and 0.2 mm for women, and normal Japanese lip protrusions to the esthetic line were 0.3 mm for men and 0.9 mm for women; for white people, these norms are ⫺4.3 mm for men and ⫺3.2 mm for women. Because the most-favored lower lip protrusions to the esthetic line were ⫺2.0 to 0 mm for men and ⫺1.5 to 0.5 mm for women, a flatter profile, more like that of white people, was favored for both Korean and Japanese sexes.
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Table.
American Journal of Orthodontics and Dentofacial Orthopedics October 2008
Range of the preferred lip protrusion values by Korean and Japanese dental students Korean dental students
Variable Upper lip protrusion (Ls to Sn-Pg=) (mm) Lower lip protrusion (Li to Sn-Pg=) (mm) Upper lip to E-line (Ls to E-line) (mm) Lower lip to E-line (Li to E-line) (mm) Nasolabial angle (Cm-Sn-Ls) (°) Z-angle (chin/lip line to FH plane) (°)
Japanese dental students
Men
Women
Men
Women
3.4-5.4 2.7-4.7 ⫺5.5-⫺3.5 ⫺2.0-0 94.0-96.0 72.0-75.0
2.5-4.5 2.4-4.4 ⫺4.5-⫺2.5 ⫺1.5-0.5 100.0-102.0 73.0-75.0
3.4-5.4 2.7-4.7 ⫺5.5-⫺3.5 ⫺2.0-0 94.0-96.0 72.0-75.0
2.5-4.5 2.4-4.4 ⫺4.5-⫺2.5 ⫺1.5-0.5 100.0-102.0 73.0-75.0
Hwang et al2 reported that the normal values of Z-angle for Korean men and women are 71.75° and 71.92°, respectively, whereas Iwasawa et al11 stated that the Z-angles for Japanese men and women are 69.7° and 71.8⬎°, respectively. We found slightly larger Z-angle values in the most-favored profiles compared with these mean values. This result might also show that Koreans and Japanese tend to prefer straighter profiles rather than convex ones. Because the mean value of the Z-angle for white people is 80.2°,12 there is still much difference between the favored Korean and Japanese Z-angles and the white norm. This might be due to the more retruded chin and generally protruding mandibular incisors inherent in Korean and Japanese populations.1,3 We established a range of soft-tissue lip position values for the most-favored Korean and Japanese profiles. These results indicate that both Korean and Japanese subjects tend to prefer lips that are slightly more retruded than the average, even though Korean and Japanese profiles have been characterized by more convex facial features. However, we should not treat all patients to the same mold. Some patients might not want their facial features to be altered to those considered as the most favored. Various racial groups can have different perceptions of what is attractive.8 CONCLUSIONS
1. Both the Korean and Japanese dental students tended to prefer slightly more retruded lip positions compared with the average silhouette, and the tendency to prefer more retruded lips was more evident for the women. 2. For men, both the Korean and Japanese dental students chose the following ranges: the mostfavored lip protrusion values relative to Sn-Pg= were 3.4 to 5.4 mm for the upper lip and 2.7 to 4.7 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺5.5 to ⫺3.5 mm for the upper lip and ⫺2.0 to 0 mm for the lower lip. The range of
most-favored nasolabial angle values associated with the most-favored profiles was 94° to 96°. The range of most-favored Z-angle values was 72° to 75°. 3. For women, both the Korean and Japanese dental students chose the following: the ranges of the mostfavored lip protrusion values relative to Sn-Pg= were 2.5 to 4.5 mm for the upper lip and 2.4 to 4.4 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺4.5 to ⫺2.5 mm for the upper lip and ⫺1.5 to 0.5 mm for the lower lip. The range of nasolabial angle values associated with the most-favored profiles was 100° to 102°. The most-favored Z-angle range was 73° to 75°. We thank Kyo-Han Kim and Gyoo-Cheon Kim for their assistance and the dental students at Kyungpook National University and Pusan National University in Korea and the dental students at Kyushu University in Japan for their participation.
REFERENCES 1. Park IC, Bowman D, Klapper L. A cephalometric study of Korean adults. Am J Orthod Dentofacial Orthop 1989;96: 54-9. 2. Hwang HS, Kim WS, McNamara JA Jr. Ethnic differences in the soft tissue profile of Korean and European-American adults with normal occlusions and well-balanced faces. Angle Orthod 2002; 72:72-80. 3. Miyajima K, McNamara JA, Kimura T, Murata S, Iizuka T. Craniofacial structure of Japanese and European-American adults with normal occlusions and well-balanced faces. Am J Orthod Dentofacial Orthop 1996;110:431-8. 4. Sarver DM, Proffit WR, Ackerman JL. Diagnosis and treatment planning in orthodontics. In: Graber TM, Vanarsdall RL Jr, editors. Orthodontics, current principles and techniques. 3rd ed. St Louis: Mosby; 2000. 5. Ioi H, Nakata S, Nakasima A, Counts AL. Anteroposterior lip positions of the most-favored Japanese facial profiles. Am J Orthod Dentofacial Orthop 2005;128:206-11. 6. Foster FJ. Profile preferences among diversified groups. Angle Orthod 1973;43:34-40.
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7. Czarnecki ST, Nanda RS, Currier GF. Perceptions of a balanced facial profile. Am J Orthod Dentofacial Orthop 1993;104:180-7. 8. Burstone CJ, Marcotte MR. Problem solving in orthodontics. Carol Stream, Ill: Quintessence; 2000. 9. Ishii K, Yamaki M, Saito I, Kaloust S, Hanada K. WWW-based investigations of profile preferences among Caucasians and Japanese. Orthod Waves 1998;57:425-30.
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10. Soh J, Chew MT, Wong HB. Professional assessment of facial profile attractiveness. Am J Orthod Dentofacial Orthop 2005;128:201-5. 11. Iwasawa T, Moro T, Nakamura K. Tweed triangle and soft-tissue consideration of Japanese with normal occlusion and good facial profile. Am J Orthod 1977;72:119-27. 12. Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. Am J Orthod 1966;52:804-22.
Comparison of anteroposterior lip positions of the most-favored facial profiles of Korean and Japanese people Hideki Ioi,a Takahiro Shimomura,b Shunsuke Nakata,c Akihiko Nakasima,d and Amy L. Countse Fukuoka, Japan, and Jacksonville, Fla Introduction: A consensus on the contemporary perception of beauty might have been developed between different countries because of increased worldwide access to variations in pleasing facial profiles. The objectives of this study were to determine, assess, and compare the ranges of values of the most-favored facial profiles rated by young Korean and Japanese adults. Methods: Average profiles were constructed from the profiles of 30 Japanese men and women with normal occlusions. A series of 13 profiles each was developed for men and women. In the series, the average profile was located in the center (number 7), and the lips were protruded or retruded in 1-mm increments from the average profile. Forty-six Korean dental students and 52 Japanese dental students were asked to rate the top 3 most-favored profiles. Results: Both the Korean and the Japanese dental students tended to select a slightly more retruded lip profile compared with the averages for men and women, and the tendency to prefer a more retruded lip position was evident for the women. Conclusions: These findings suggest that young Korean and Japanese adults prefer a retruded profile, even though their profiles have historically been characterized by more convex facial features. (Am J Orthod Dentofacial Orthop 2008;134:490-5)
T
reatment-planning goals for orthodontics and orthognathic surgery are based on established normal values for each ethnic group. For example, the average anteroposterior lip position in Japanese adults is relatively more protrusive than that of white people. The same observation in Korean adults has been reported in previous studies.1,2 Regarding hardand soft-tissue measurements, both Japanese and Koreans have a more retruded chin position, protruding mandibular incisors, and more protruded lip positions compared with white norms.1-3 It is important to consider the perceptions of nonorthodontists in determining the most pleasant profile because the goals of orthodontic treatment are not only to achieve a functional occlusion, but also to create an esthetic profile.4 a
Lecturer, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. Resident, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. c Associate professor, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. d Professor, Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. e Professor, Dental School of Orthodontics, Jacksonville University, Jacksonville, Fla. Reprint requests to: Hideki Ioi, Department of Orthodontics, Faculty of Dentistry, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; e-mail, [email protected]. Submitted, July 2006; revised and accepted, September 2006. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.09.070 b
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We previously reported on the Japanese perception of the most-favored profiles rated by orthodontists and dental students.5 However, no reports have attempted to compare and quantify soft-tissue lip positions of the most-favored profiles between Korean and Japanese subjects. Korean and Japanese people originated from the same racial group and have similar cultural backgrounds. Moreover, young adults experience great exposure to mass media—television, movies, the Internet, and travel. The perception of a pleasing facial profile can differ between 2 countries or might be changing to a more internationally pleasing one. In light of these facts, we aimed to determine the most pleasing profiles for young Korean and Japanese adults. Facial silhouettes were chosen for rating the profiles, rather than facial photos, to avoid subjective considerations.6,7 The purposes of this study were to determine, assess, and compare the range of soft-tissue anteroposterior lip position of the top 3 most-favored profiles rated by young Korean and Japanese adults from a series of varying lip positions in facial silhouettes. MATERIAL AND METHODS
Average Japanese silhouettes were constructed from 30 cephalometric radiographs (15 men, 15 women) of Japanese adults aged 22 to 26 years. Inclusion criteria for this study were ANB angle between 2° and 5°, normal occlusion with minor or no crowding, all teeth present
Ioi et al 491
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RESULTS
Fig 1. Soft tissue cephalometric reference points and analyses: 1, upper lip protrusion (Ls to Sn-Pg=); 2, lower lip protrusion (Li to Sn-Pg=); 3, upper lip to E-line (Ls to E-line); 4, lower lip to E-line (Li to E-line); 5, nasolabial angle (Cm-Sn-Ls); 6, Z-angle (chin/lip line to FH plane).
except third molars, no previous orthodontic treatment, and no prosthetic replacement of teeth. The details of constructing the average profile were given in a previous article.5 Soft-tissue reference points and angles are shown in Figure 1. We obtained 4 linear and 2 angular measurements for the soft-tissue analysis. A series of 13 profiles was developed and arranged for men and women on the paper, respectively (Fig 2). In the series, the average profile (number 7) was in the center position. The lips were protruded or retruded in 1-mm increments from the average profile, and the lip positions were changed parallel to the Frankfort horizontal plane. Profile number 1 was the most retrusive, and number 13 was the most protrusive. The profile raters were 46 Korean dental students (32 men, 14 women; age, 24.2 ⫾ 2.0 years) from Kyungpook National University in Daegu and Pusan National University in Pusan, Korea, and 52 Japanese dental students (35 men 17 women; age, 24.5 ⫾ 2.1 years) from Kyushu University in Fukuoka, Japan. They were asked to choose the top 3 most-favored profiles. Statistical analysis
The Fisher exact probability tests were used to compare the differences in the scores between the top 3 most-favored profiles and the other profiles, and to compare the distribution of the 3 most-favored profiles between the Koreans and Japanese. Probability of less than .05 was considered statistically significant.
For the Korean dental students, the top 3 male profiles were numbers 5, 6, and 4 (Fig 3), and the most-favored female profiles were numbers 4, 3, and 5 (Fig 4). The scores for the top 3 male profiles were significantly greater than for the other profiles (P ⬍0.05). On the other hand, the scores for the top 3 female profiles were significantly greater than the other profiles (P ⬍0.05), except between numbers 2 and 3, numbers 2 and 5, and numbers 5 and 6. For the Japanese dental students, the 3 most-favored male profiles were numbers 5, 6, and 4 (Fig 3), and the 3 most-favored female profiles were numbers 3, 4, and 5 (Fig 4). The scores in the top 3 male profiles were significantly greater than for the other profiles (P ⬍0.05), except between numbers 4 and 7, and numbers 6 and 7. On the other hand, the scores for the top 3 female profiles were significantly greater than for the other profiles (P ⬍0.05), except between numbers 2 and 5, numbers 3 and 6, numbers 4 and 6, and numbers 5 and 6. There was no significant difference in the distribution of the top 3 most-favored profiles between the Koreans and the Japanese. From these most-favored profiles, rated by Korean and Japanese dental students, the ranges of the following soft-tissue measurements were determined: lip protrusion to Sn-Pg= or the esthetic line, nasolabial angle associated with the most-favored profiles, and Z-angle for men and women (Table). For men, both the Korean and Japanese dental students chose the following ranges: the mostfavored lip protrusion values relative to Sn-Pg= were 3.4 to 5.4 mm for the upper lip and 2.7 to 4.7 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺5.5 to ⫺3.5 mm for the upper lip and ⫺2.0 to 0 mm for the lower lip. The range of mostfavored nasolabial angle values associated with the mostfavored profiles was 94° to 96°. The range of mostfavored Z-angle values was 72° to 75°. For women, both the Korean and Japanese dental students chose the following ranges: the ranges of the most-favored lip protrusion values relative to Sn-Pg= were 2.5 to 4.5 mm for the upper lip and 2.4 to 4.4 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺4.5 to ⫺2.5 mm for the upper lip and ⫺1.5 to 0.5 mm for the lower lip. The range of nasolabial angle values associated with the most-favored profiles was 100° to 102°. The most-favored Z-angle range was 73° to 75°. DISCUSSION
In this study, Japanese samples were used for constructing the average facial profiles. Although Korean and
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Fig 2. Series of 13 profiles rated by Korean and Japanese dental students for men (upper row) and women (lower row).
Japanese people are the same racial group, the normal values of cephalometric hard- and soft-tissue measurements can differ between them. Because we confirmed that the normal values of lip protrusion were similar (Korean men and women, 0.7 ⫾ 2.7 and 0.2 ⫾ 1.7 mm, respectively; Japanese men and women, 0.3 ⫾ 2.6 and 0.9 ⫾ 1.9 mm, respectively),1,3 we decided to use the same series of facial profiles in this study and made the number 7 profile the average in both groups. Moreover, we considered that the same facial profiles could shed light on the differences of facial preference between the 2 countries. The objectives of orthodontic treatment are to achieve facial balance, through stabilization of the dentition, and to produce pleasing facial and dental esthetics.8 Therefore, it is important to identify and define the characteristics of a pleasing face, as well as those of a functioning occlusion. Our predecessors, including philosophers and artists, attempted to define beauty. However, it was difficult to determine the standards of beauty, because of tremendous variations among people in different racial groups.8 To date, no studies have attempted to compare and quantify soft-tissue lip positions of the most-favored profiles between Korean and Japanese subjects. Because the perception of beauty might differ between the 2 countries, it
appears reasonable to evaluate the most pleasing faces of Koreans and Japanese. Worldwide communications through the media, such as the Internet, television, movies, and magazines, have expanded in recent years. People who are potential candidates for orthodontic treatment are likely to be profoundly influenced by these media. Our hypothesis was that there might be consensus on the contemporary perception of beauty between different countries because of increased worldwide access to variations in pleasing facial profiles. Our objectives were to determine, assess, and compare the values of the mostfavored facial profiles rated by Korean and Japanese dental students. The Korean dental students rated the most-favored profiles as slightly more retruded compared with the average for both men and women. If the raters in this study chose the average profile as the most-favored one, they would have selected number 7. Number 5 was considered the most favored for men and number 4 for women. The tendency was to prefer an even more slightly retruded lip position than the average lip position for women. On the other hand, the Japanese dental students regarded number 5 as the best profile for men and number 3 or 4 as the
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Fig 3. Distribution of the most-favored male profiles rated by the Korean and Japanese dental students.
Fig 4. Distribution of the most-favored female profiles rated by the Korean and Japanese dental students.
best for women. Young Korean and Japanese adults have similar perceptions of the most-favored facial profiles: they preferred slightly more retruded lip positions compared with the average for both men and women, and this tendency was more evident for the women. They preferred a slightly retruded lip position, even though their profiles were characterized by convex features.1,2,9 Soh et al10 reported that normal and bimaxillary retrusive Chinese male and female profiles were judged to be highly attractive by orthodontists and oral surgeons. These results might imply that a perception of beauty could have been established across the borders of Asian countries. For men and women, the Korean and Japanese
dental students preferred the same ranges of favored lip protrusion relative to Ls to Sn-Pg=, Li to Sn-Pg=, Ls to E-line, Li to E-line, nasolabial angle, and Z-angle, respectively. Park et al1 and Miyajima et al3 reported that normal Korean lip protrusions to the esthetic line were 0.7 mm for men and 0.2 mm for women, and normal Japanese lip protrusions to the esthetic line were 0.3 mm for men and 0.9 mm for women; for white people, these norms are ⫺4.3 mm for men and ⫺3.2 mm for women. Because the most-favored lower lip protrusions to the esthetic line were ⫺2.0 to 0 mm for men and ⫺1.5 to 0.5 mm for women, a flatter profile, more like that of white people, was favored for both Korean and Japanese sexes.
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Table.
American Journal of Orthodontics and Dentofacial Orthopedics October 2008
Range of the preferred lip protrusion values by Korean and Japanese dental students Korean dental students
Variable Upper lip protrusion (Ls to Sn-Pg=) (mm) Lower lip protrusion (Li to Sn-Pg=) (mm) Upper lip to E-line (Ls to E-line) (mm) Lower lip to E-line (Li to E-line) (mm) Nasolabial angle (Cm-Sn-Ls) (°) Z-angle (chin/lip line to FH plane) (°)
Japanese dental students
Men
Women
Men
Women
3.4-5.4 2.7-4.7 ⫺5.5-⫺3.5 ⫺2.0-0 94.0-96.0 72.0-75.0
2.5-4.5 2.4-4.4 ⫺4.5-⫺2.5 ⫺1.5-0.5 100.0-102.0 73.0-75.0
3.4-5.4 2.7-4.7 ⫺5.5-⫺3.5 ⫺2.0-0 94.0-96.0 72.0-75.0
2.5-4.5 2.4-4.4 ⫺4.5-⫺2.5 ⫺1.5-0.5 100.0-102.0 73.0-75.0
Hwang et al2 reported that the normal values of Z-angle for Korean men and women are 71.75° and 71.92°, respectively, whereas Iwasawa et al11 stated that the Z-angles for Japanese men and women are 69.7° and 71.8⬎°, respectively. We found slightly larger Z-angle values in the most-favored profiles compared with these mean values. This result might also show that Koreans and Japanese tend to prefer straighter profiles rather than convex ones. Because the mean value of the Z-angle for white people is 80.2°,12 there is still much difference between the favored Korean and Japanese Z-angles and the white norm. This might be due to the more retruded chin and generally protruding mandibular incisors inherent in Korean and Japanese populations.1,3 We established a range of soft-tissue lip position values for the most-favored Korean and Japanese profiles. These results indicate that both Korean and Japanese subjects tend to prefer lips that are slightly more retruded than the average, even though Korean and Japanese profiles have been characterized by more convex facial features. However, we should not treat all patients to the same mold. Some patients might not want their facial features to be altered to those considered as the most favored. Various racial groups can have different perceptions of what is attractive.8 CONCLUSIONS
1. Both the Korean and Japanese dental students tended to prefer slightly more retruded lip positions compared with the average silhouette, and the tendency to prefer more retruded lips was more evident for the women. 2. For men, both the Korean and Japanese dental students chose the following ranges: the mostfavored lip protrusion values relative to Sn-Pg= were 3.4 to 5.4 mm for the upper lip and 2.7 to 4.7 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺5.5 to ⫺3.5 mm for the upper lip and ⫺2.0 to 0 mm for the lower lip. The range of
most-favored nasolabial angle values associated with the most-favored profiles was 94° to 96°. The range of most-favored Z-angle values was 72° to 75°. 3. For women, both the Korean and Japanese dental students chose the following: the ranges of the mostfavored lip protrusion values relative to Sn-Pg= were 2.5 to 4.5 mm for the upper lip and 2.4 to 4.4 mm for the lower lip. The most-favored lip protrusion ranges relative to the esthetic line were ⫺4.5 to ⫺2.5 mm for the upper lip and ⫺1.5 to 0.5 mm for the lower lip. The range of nasolabial angle values associated with the most-favored profiles was 100° to 102°. The most-favored Z-angle range was 73° to 75°. We thank Kyo-Han Kim and Gyoo-Cheon Kim for their assistance and the dental students at Kyungpook National University and Pusan National University in Korea and the dental students at Kyushu University in Japan for their participation.
REFERENCES 1. Park IC, Bowman D, Klapper L. A cephalometric study of Korean adults. Am J Orthod Dentofacial Orthop 1989;96: 54-9. 2. Hwang HS, Kim WS, McNamara JA Jr. Ethnic differences in the soft tissue profile of Korean and European-American adults with normal occlusions and well-balanced faces. Angle Orthod 2002; 72:72-80. 3. Miyajima K, McNamara JA, Kimura T, Murata S, Iizuka T. Craniofacial structure of Japanese and European-American adults with normal occlusions and well-balanced faces. Am J Orthod Dentofacial Orthop 1996;110:431-8. 4. Sarver DM, Proffit WR, Ackerman JL. Diagnosis and treatment planning in orthodontics. In: Graber TM, Vanarsdall RL Jr, editors. Orthodontics, current principles and techniques. 3rd ed. St Louis: Mosby; 2000. 5. Ioi H, Nakata S, Nakasima A, Counts AL. Anteroposterior lip positions of the most-favored Japanese facial profiles. Am J Orthod Dentofacial Orthop 2005;128:206-11. 6. Foster FJ. Profile preferences among diversified groups. Angle Orthod 1973;43:34-40.
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7. Czarnecki ST, Nanda RS, Currier GF. Perceptions of a balanced facial profile. Am J Orthod Dentofacial Orthop 1993;104:180-7. 8. Burstone CJ, Marcotte MR. Problem solving in orthodontics. Carol Stream, Ill: Quintessence; 2000. 9. Ishii K, Yamaki M, Saito I, Kaloust S, Hanada K. WWW-based investigations of profile preferences among Caucasians and Japanese. Orthod Waves 1998;57:425-30.
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10. Soh J, Chew MT, Wong HB. Professional assessment of facial profile attractiveness. Am J Orthod Dentofacial Orthop 2005;128:201-5. 11. Iwasawa T, Moro T, Nakamura K. Tweed triangle and soft-tissue consideration of Japanese with normal occlusion and good facial profile. Am J Orthod 1977;72:119-27. 12. Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. Am J Orthod 1966;52:804-22.