Effects of transverse relationships between maxillary arch, mouth, and face on smile esthetics.
OBJECTIVE
To identify the ideal ratios between the widths of the maxillary arch, mouth, and face, respectively, and to determine the range of acceptable esthetic variations based on these ideal ratios.


METHODS
A photograph of a young female with a harmonious smile was selected and digitally altered to produce two sets of images. The first image showed an altered intercanine width, while the second one showed an altered oral fissure breadth. These alterations were independently rated by judges, including 23 orthodontists and 30 undergraduates. The Mann-Whitney U-test was used to compare the scores given by male and female judges and those given by professional and nonprofessional judges.


RESULTS
The following ideal transverse ratios were determined: intercanine width/oral fissure breadth, 0.638; oral fissure breadth/interparopia width: the distance between left and right paropia, 0.617; and intercanine width/face width at the level of the labial commissures, 0.300. A range of -10% to +10% was proposed as the thresholds of esthetic smile evaluations. It was shown that gender of the raters had no effect on the rating of photographs, nor were there any statistically significant differences between the professional and nonprofessional judges' ratings.


CONCLUSIONS
Balanced transverse relationships in the facial region are important for smile esthetics, and there is a wide range of esthetically acceptable variations in the transverse relationships between the maxillary arch, mouth, and face.
a  Lecturer, Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China.
Ke
K
Zhang
b  Lecturer, Department of Orthodontics, School of Stomatology, Chongqing Medical University, Chongqing, China.
Lan
L
Huang
c  Lecturer, Department of Stomatology, The Third People's Hospital of Chengdu, Sichuan, China.
Lin
L
Yang
d  Graduate student, State Key Laboratory of Oral Diseases (Sichuan University); Department of Orthodontics, West China Stomatological Hospital, Sichuan University, Sichuan, China.
Li
L
Xu
d  Graduate student, State Key Laboratory of Oral Diseases (Sichuan University); Department of Orthodontics, West China Stomatological Hospital, Sichuan University, Sichuan, China.
Chaoran
C
Xue
d  Graduate student, State Key Laboratory of Oral Diseases (Sichuan University); Department of Orthodontics, West China Stomatological Hospital, Sichuan University, Sichuan, China.
Zichao
Z
Xiang
d  Graduate student, State Key Laboratory of Oral Diseases (Sichuan University); Department of Orthodontics, West China Stomatological Hospital, Sichuan University, Sichuan, China.
Mengyuan
M
Zhao
e  Professor, Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China.
Song
S
Li
e  Professor, Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China.
Yuxing
Y
Bai
f  Professor and Chair, Department of Orthodontics, West China Stomatological Hospital; State Key Laboratory of Oral Diseases, Sichuan University, Sichuan, China.
Ding
D
Bai
D004955:Esthetics, Dental; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla / Q000033:anatomy & histology*; D012904:Smiling
Orthodontics; Smile esthetics; Transverse relationship