Esthetic preferences for the shape of anterior teeth in a posed smile

Introduction

Although various aspects of smile esthetics have been considered in many studies, few of them have compared laypeople’s preferences for an esthetic smile with regard to the shape of the anterior teeth. The aim of this study was to evaluate the effects of the shapes of the maxillary anterior teeth in men and women on the perception of an esthetic smile by different age and sex groups of laypeople.

Methods

Two pamphlets, each consisting of 9 smile images that differed only in the shapes of the canines and incisors, were shown to 4 groups of judges of different ages and sexes. They were asked to rank feminine and masculine smile images according to their preferences using a 10-cell linear horizontal visual analog scale.

Results

Neither in the men’s nor in the women’s pamphlets were there significant differences between the scores of the 4 groups of judges to the various tooth forms. In both pamphlets, regardless of canine shape, all groups of judges gave significantly different scores to square, square-round, and round incisors so that the median of scores for square incisors was significantly lower than those of the 2 other incisor forms.

Conclusions

Sex and age of the laypersons did not affect their esthetic perception of the shapes of the maxillary anterior teeth. Incisor shape was the key determinant of their esthetic preferences; round incisors were the most esthetic. It is recommended to improve smile esthetics by mildly rounding the mesial and distal corners of square incisors.

Psychological studies have shown that facial attractiveness affects the way a person is treated by others. The perception of esthetics is completely subjective and influenced by many factors including culture, social status, and level of education. In modern societies, a pleasant smile is an advantage in job interviews, social interactions, and even the selection of a spouse. Various aspects of smile esthetics have been considered in many studies. Vig and Brundo, Mikami, and van der Geld and van Waas evaluated the amounts of incisor display and the positions of the smile line. Ackerman and Ackerman and Nanda and Burstone explained and assessed the role of buccal corridors in smile attractiveness. Sarver defined and categorized different types of smile arc and its relevance to smile esthetics. Van der Geld et al investigated self-perceptions of smile attractiveness and determined the role of the smile line and other aspects correlated with smile attractiveness and their influence on personality traits. Parekh et al evaluated the esthetic acceptability range of computer-generated variations in smile arc and buccal corridor. Another important aspect in smile esthetics is the shape of the maxillary anterior teeth, which are most frequently seen during a smile. Few studies have compared laypeople’s preferences for an esthetic smile with regard to the shape of the anterior teeth. The aim of this study was to evaluate how different sex and age groups of lay judges rank masculine and feminine smiles with various shapes of maxillary anterior teeth according to their esthetic preferences.

Material and methods

In this study, 2 pamphlets, each consisting of 9 smile images, were shown to the judges, who were asked to rank them according to their preferences using a 10-cell linear horizontal visual analog scale (VAS).

To prepare the pamphlets, first, we found beautiful posed smile images of women with normal dentofacial relationships and determined which possessed the esthetic features of an ideal smile according to previous studies. To reduce the number of confounding variables, this image only included a smile framework, with no other parts of the face. Then, using Adobe Photoshop (version CS3, Adobe Systems, San Jose, Calif) for each sex, we made 3 groups of images. In the first group, with the maxillary canine cusps kept pointed, the maxillary central and lateral incisor edges were altered to square, square-round, or round to create 3 smile images. In the second group, the maxillary canine cusps were rounded, and, similarly, the maxillary central and lateral incisor edges were altered to square, square-round, or round. In the third group, the canines were given a flat cusp, and the changes in the shapes of the maxillary incisors were made in the same manner. Thus, 9 smile images that were different only in the shapes of the maxillary anterior teeth were prepared. Three of these images were printed in color on 1 page to make a 3-page pamphlet of feminine smiles ( Fig 1 ).

Fig 1
The 3-page pamphlet of feminine smiles. From top to bottom, page 1 shows a pointed canine with round, square-round, and square incisors. On pages 2 and 3, only the canine shape has been altered to round and flat, respectively.

The pamphlet of masculine smiles was made just by altering the lip pattern and skin color of the corresponding feminine smiles to resemble a man’s lips and complexion ( Fig 2 ).

Fig 2
The 3-page pamphlet of masculine smiles. From top to bottom, page 1 shows a pointed canine with round, square-round, and square incisors. On pages 2 and 3, only the canine shape has been altered to round and flat, respectively.

A total of 100 laypersons who were admitted to a private office for the first visit were selected as the judges: 50 men, half in the 15-to-25-year-old age group and the other half in the 40-to-50-year-old age group, and 50 women categorized in the same way. The age range of 15 to 25 is the approximate age of most orthodontic patients, and the range of 40 to 50 is that of their parents.

The judges were requested to write their sex and age on the pamphlets and then concentrate on the maxillary teeth while looking at each smile image, keeping in mind the sex of the smile owner. The participants then were asked to put a check mark on the VAS next to each image to define its attractiveness, taking into consideration that, on the VAS, 1 meant the least attractive and 10 indicated the most attractive smile.

Because the measuring scale was ordinal, the median was used to describe the data. The nonparametric tests of Kruskal-Wallis, Friedman, and Wilcoxon of SPSS software for Windows (version15.0, SPSS, Chicago, Ill) were used for data analysis.

Results

According to the Kruskal-Wallis test, neither in the men’s nor in the women’s pamphlets were there significant differences between the scores of the 4 groups of judges for the various tooth forms ( Tables I and II ).

Table I
Median scores in the women’s pamphlet
Tooth shapes Judges’ group
15-25-year-old men 40-50-year-old men 15-25-year-old women 40-50-year-old women P
Flat canine,
round incisors
8.00 8.00 9.00 8.00 0.296
Flat canine,
square-round incisors
8.00 8.00 9.00 9.00 0.080
Flat canine,
square incisors
6.00 6.00 6.00 4.00 0.419
Round canine,
round incisors
9.00 9.00 10.00 10.00 0.076
Round canine,
square-round incisors
8.00 7.00 8.00 7.00 0.644
Round canine,
square incisors
5.00 4.00 5.00 5.00 0.586
Pointed canine,
round incisors
8.00 8.00 8.00 8.00 0.959
Pointed canine,
square-round incisors
8.00 8.00 8.00 7.00 0.483
Pointed canine,
square incisors
5.00 5.00 5.00 5.00 0.910

Kruskal-Wallis test.

Table II
Median scores in the men’s pamphlet
Tooth shapes Judges’ group
15-25-year-old men 40-50-year-old men 15-25-year-old women 40-50-year-old women P
Flat canine,
round incisors
9.00 9.00 9.00 8.00 0.080
Flat canine,
square-round incisors
9.00 9.00 9.00 10.00 0.808
Flat canine,
square incisors
4.00 6.00 6.00 4.00 0.186
Round canine,
round incisors
9.00 9.00 9.00 9.00 0.868
Round canine,
square-round incisors
8.00 8.00 8.00 8.00 0.857
Round canine,
square incisors
6.00 5.00 6.00 4.00 0.566
Pointed canine,
round incisors
8.00 8.00 9.00 9.00 0.997
Pointed canine,
square-round incisors
8.00 7.00 9.00 7.00 0.629
Pointed canine,
square incisors
5.00 5.00 5.00 5.00 0.883

Kruskal-Wallis test.

With the Friedman test, in each group of judges, the scores given to the various tooth forms were significantly different ( P <0.001) in both pamphlets. The Wilcoxon test, therefore, was used to find the differences ( Tables III-VI ).

Table III
Wilcoxon P values of men’s and women’s pamphlets assessed by 15-25-year-old male judges
Women’s
Men’s Flat canine,
round incisors
Flat canine,
square-round incisors
Flat canine,
square incisors
Round canine,
round incisors
Round canine,
square-round incisors
Round canine,
square incisors
Pointed canine,
round incisors
Pointed canine,
square-round incisors
Pointed canine,
square incisors
Flat canine,
round incisors
0.348 0.018 0.826 0.020 0.006 0.826 0.059 0.002
Flat canine,
square-round incisors
0.202 0.011 0.018 0.266 0.008 0.458 0.348 0.002
Flat canine,
square incisors
<0.001 <0.001 0.015 0.044 0.287 0.003 0.017 0.638
Round canine,
round incisors
0.691 0.191 <0.001 0.009 0.005 0.395 0.076 <0.001
Round canine,
square-round incisors
1.000 0.021 <0.001 0.590 0.014 0.031 0.820 0.006
Round canine,
square incisors
0.013 <0.001 0.164 0.009 <0.001 <0.001 0.001 0.797
Pointed canine,
round incisors
0.868 0.057 <0.001 0.193 0.940 0.004 0.046 0.004
Pointed canine,
square-round incisors
0.522 0.004 0.001 0.129 0.103 0.004 0.219 0.010
Pointed canine,
square incisors
0.022 <0.001 0.441 0.006 <0.001 0.949 0.005 0.006

Significant value.

Table IV
Wilcoxon P values of men’s and women’s pamphlet assessed by 40-50-year-old male judges
Women’s
Men’s Flat canine,
round incisors
Flat canine,
square-round incisors
Flat canine,
square incisors
Round canine,
round incisors
Round canine,
square-round incisors
Round canine,
square incisors
Pointed canine,
round incisors
Pointed canine,
square-round incisors
Pointed canine,
square incisors
Flat canine,
round incisors
0.243 <0.001 0.703 0.007 <0.001 0.231 <0.001 0.001
Flat canine,
square-round incisors
0.905 <0.001 0.129 0.176 <0.001 0.539 0.087 0.002
Flat canine,
square incisors
<0.001 <0.001 0.001 0.001 0.056 0.001 0.006 0.611
Round canine,
round incisors
0.332 0.071 <0.001 0.007 <0.001 0.381 0.030 0.001
Round canine,
square-round incisors
0.119 0.006 <0.001 0.286 <0.001 0.014 0.732 0.009
Round canine,
square incisors
<0.001 <0.001 0.230 <0.001 <0.001 <0.001 <0.001 0.040
Pointed canine,
round incisors
0.170 0.016 <0.001 0.106 0.923 <0.001 0.017 0.003
Pointed canine,
square-round incisors
0.005 <0.001 0.007 0.002 0.001 <0.001 0.005 0.007
Pointed canine,
square incisors
<0.001 <0.001 0.237 <0.001 <0.001 0.661 <0.001 0.009

Significant value.

Table V
Wilcoxon P values of men’s and women’s pamphlets assessed by 15-25-year-old female judges
Women’s
Men’s Flat canine,
round incisors
Flat canine,
square-round incisors
Flat canine,
square incisors
Round canine,
round incisors
Round canine,
square-round incisors
Round canine,
square incisors
Pointed canine,
round incisors
Pointed canine,
square-round incisors
Pointed canine,
square incisors
Flat canine,
round incisors
0.753 <0.001 0.081 0.004 <0.001 0.178 <0.001 0.004
Flat canine,
square-round incisors
0.116 <0.001 0.008 0.013 <0.001 0.297 0.014 0.001
Flat canine,
square incisors
<0.001 <0.001 <0.001 <0.001 0.413 <0.001 <0.001 0.133
Round canine,
round incisors
0.242 0.501 <0.001 <0.001 <0.001 0.007 0.001 <0.001
Round canine,
square-round incisors
0.951 0.025 <0.001 0.241 <0.001 0.132 0.528 0.031
Round canine,
square incisors
<0.001 <0.001 0.209 <0.001 <0.001 <0.001 <0.001 0.047
Pointed canine, round incisors 0.932 0.016 <0.001 0.032 0.840 <0.001 0.053 0.006
Pointed canine,
square-round incisors
0.289 0.010 0.001 0.045 0.038 <0.001 0.264 0.010
Pointed canine,
square incisors
<0.001 <0.001 0.236 <0.001 <0.001 0.756 <0.001 0.002
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Apr 11, 2017 | Posted by in Orthodontics | Comments Off on Esthetic preferences for the shape of anterior teeth in a posed smile
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