Material and methods

The first preliminary step for the development of this project was to obtain models for background facial images to be used in the study. Potential models were recruited at Ohio State University, Columbus. Two frontal full-face digital images were obtained for each consenting subject (EOS Digital Rebel XT camera, Canon, Melville, NY)- 1 social smile where the participants showed the teeth and 1 photo with no teeth visible. Facial attractiveness was rated from the image with no teeth visible to avoid the potential that the facial attractiveness of the models would be affected by their natural dentition.

Model images were excluded that were judged by the researchers to have a significant distraction, such as a facial tattoo, extreme facial hair or hairstyle, asymmetry, abnormal piercing, and so on. Models were 18 to 30-year-old white men in an attempt to eliminate the variable of ethnicity and to control for sex. In total, 109 facial images were collected and included for the background facial attractiveness ratings.

The images showing no teeth were rated by peer young adults who had no background or formal education in dentistry (laypersons). They rated the images as attractive, average, or unattractive, or 3, 2, and 1, respectively. Reliability was determined by repeating all images in random order during the same rating session. Twenty raters evaluated the images, and reliabilities were good for intrarater (weighted kappa, 0.67; 95% confidence interval [CI], 0.64-0.70) and poor for interrater (weighted kappa, 0.35; 95% CI, 0.34-0.37).

The images were selected based on the mean value of the ratings. The 3 images with the highest mean closest to 3 were selected as attractive, the 3 closest to 2 were selected as average, and the lowest 3 image means were selected as unattractive. This provided the greatest spread among the images for the level of facial attractiveness.

Frontal facial images of various levels of dental esthetics were then selected from the database of the Ohio State University orthodontic clinical archive. These images were classified in accordance with the IOTN-AC by researchers. The IOTN-AC is based on 10 levels of malocclusion defined by esthetic impairment, a method that was tested for reliability and validity by Richmond and described by Borzabadi-Farahani. Level 1 represents the least treatment need, level 7 is the upper limit of borderline need, and level 10 is a clear need for treatment based on esthetic grounds. To verify the researchers’ classifications of the IOTN-AC level, experienced orthodontists (15 full-time and part-time university faculty) were surveyed to verify agreement with the level of malocclusion as defined by the IOTN-AC. All images were rated twice to determine reliability. The details of this method have been previously described. The intrarater kappa statistic was 0.72 with 91.7% agreement, and the interrater kappas statistic was 0.56 with 83.1% agreement for all images.

Next, the selected background facial attractiveness model smiling images were combined with the verified IOTN dental esthetic-level images. The models for each background attractiveness level were drawn randomly for combination with 1 of the 3 IOTN malocclusion levels: 1, 7, or 10. Composite images were created using Photoshop Elements 11 software (Adobe Systems, San Jose, Calif) by removing the models’ existing dentition and creating a new layer for the verified IOTN esthetic level, with adjustments for scale and color as needed. The backgrounds of all images were standardized with a basic gray hue, and the scale of each model’s head in the background was visually standardized between all images. In total, 9 composite images were generated, 1 for each malocclusion and attractiveness level: attractive IOTN 1, attractive IOTN 7, attractive IOTN 10, average IOTN 1, average IOTN 7, average IOTN 10, unattractive IOTN 1, unattractive IOTN 7, and unattractive IOTN 10 ( Fig 1 ). In a previous study with facial images of women, reliability in each dental and facial attractiveness level was established; thus, for this study with men, only 1 image per level was used.

All combinations of facial attractiveness and IOTN-AC levels used in this study.

Interest areas for the 9 composite images were defined (Experiment Builder; SR Research, Mississauga, Ontario, Canada). The areas mapped were eyes, nose, mouth, ears, eyebrows, chin, hair, and cheeks ( Fig 2 ). To simplify the analysis, the areas were classified as eye, nose, mouth, chin, ear, and other (including hair, eyebrows, cheeks, and so on).

Example of composite image (unattractive model, IOTN level 10) with mapped interest areas ( peach ) and eye-tracking data recorded ( blue ).

The eye-tracking camera used for the experiment, Eyelink 1000 (SR Research) has a reported average accuracy of 0.25° to 0.5°. For this reason, some space was left between the mapped areas to allow for this degree of error.

Institutional review board approval was obtained for the study (Behavioral Sciences IRB #2012B0414). Raters were recruited on a university campus. Inclusion criteria for raters were set as follows: 18 to 30 years old, able to understand English, no known neurologic conditions, normal or corrected to normal color vision (no hard contact lenses), willing to attend 20 to 25-minute eye-tracking sessions, no recent consumption of drugs or alcohol, no current medications that could affect cognitive abilities, and no mascara or willing to remove it as needed for the session. Dental professionals and dental students were excluded, with the intent of a layperson perspective for the study.

Written informed consent was obtained for all raters. Deception was used so that the raters were not more prone to look at the mouth. Raters were told that this was a study to look at how people view faces, and a debriefing form was given after the study to inform the participants of the actual nature of the study. Additionally, a short questionnaire was given that inquired about the rater’s age, ethnicity, and sex.

Raters were positioned in a table-mounted head-stabilizing device. Each rater was calibrated on a 9 or 5 point calibration with the eye tracker and instructed how the program would run. The eye-tracking data were captured using Data Viewer software (SR Research) for duration of fixations (total time in milliseconds spent viewing each interest area) and density of fixations (total number of fixations in each interest area).

The 9 composite male images were presented in a different order to each subject, and the randomization was determined by the computer program. Five sample images were viewed before the experimental images to allow the participants to familiarize themselves with the program and how it would run before any data were collected. All images were repeated a second time, again in a computer-determined random order, for reliability. To summarize, each subject saw 5 practice images, rated 9 images, and rerated 9 images for reliability for a total of 23 images. Each was viewed for 3 seconds. A flowchart of the procedures is included ( Fig 3 ). Between each image, a cross was displayed in a random changing location on a blank screen to eliminate the possibility that the location of the gaze was fixed from 1 image to the next. A total of 87 subjects consented for the experiment, and 23 were excluded. Eight were excluded for the inability to calibrate them in the eye tracker, 1 was excluded for not completing the demographic information, and 14 were excluded for being of a different race than white. This gave a total of 64 participants meeting the inclusion criteria; 41 were male, and 23 were female.

Flowchart outlining the steps in the study.

Results

Density was the measure of the total number of fixations in an interest area, and duration was the total time in milliseconds that the observer spent viewing a given interest area. Reliability was assessed; an intraclass correlation coefficient less than 0.40 was poor, 0.40 to 0.59 was fair, 0.60 and 0.74 was good, and greater than 0.75 was excellent. Intrarater and interrater reliabilities were good and excellent in the areas of eye, nose, and mouth for both density and duration of fixations (0.6-0.91). For this reason, these were the areas included in the data analysis. The reliability for the areas of chin, ear, and other had poor reliability in either density or duration, and were eliminated from the data analysis.

For density, significant interactions were seen for the variables of model facial attractiveness and area of the face ( P <0.0004), dental esthetic level and area of the face ( P <0.0001), and area of the face and rater sex ( P = 0.0098). Additionally, the main effects of area of the face were also significant ( P <0.0001). For facial attractiveness by area of the face ( Fig 4 ) in men of average attractiveness, the mouth received significantly more visual attention than it did in the unattractive ( P = 0.0023) and attractive ( P <0.0478) men. In average men, the mouth exceeded both the eye and the nose ( P <0.0001). For unattractive and attractive men, the hierarchy for visual attention was the same: the greatest density at the eyes followed by the mouth and the nose. The eyes were significantly different from the nose in both cases ( P <0.0001).

Density results: area by facial attractiveness, area by dental esthetics, and area by rater sex.

For dental esthetic level and area of the face ( Fig 4 ), with no treatment need (IOTN 1), the eye received significantly more visual attention than did the mouth ( P <0.0001). For subjects with borderline dental esthetics (IOTN 7), the mouth had significantly more visual attention than it did for subjects in IOTN 1 ( P = 0.0014) and significantly more than the nose ( P = 0.0001), but it was not statistically distinguishable from the eye. At IOTN 10, the mouth received significantly more visual attention than it did in the borderline models (IOTN 7) ( P <0.0001), and it significantly exceeded the eye ( P <0.0001) and the nose ( P <0.0001).

For area of the face and rater sex ( Fig 4 ), both male and female raters gave significantly more visual attention to the eyes than the nose ( P <0.0007 and P = 0.0001, respectively). Women gave significantly more visual attention to the eyes than did the men ( P = 0.0226). Male raters showed significantly more visual attention to the mouth than the nose ( P = 0.0001).

For duration, the pattern was the same as for density. Significant interactions were found in the same areas: model facial attractiveness and area of the face ( P <0.0013), dental esthetic level and area of the face ( P <0.0001), and area of the face and rater sex ( P = 0.0087). Additionally, the main effects of dental esthetics (occlusion) and area of the face were significant ( P <0.0018 and P <0.0001, respectively).

For facial attractiveness by area of the face ( Fig 5 ), again significant differences were seen in duration, with men of average attractiveness receiving more visual attention to the mouth than the unattractive ( P = 0.0447) and attractive ( P <0.0030) models. Again, the hierarchy for unattractive and attractive men was eye, mouth, and nose, with the eye receiving significantly more visual attention than the nose ( P = 0.0001, unattractive; P <0.0001, attractive), but only more than the mouth for attractive men. For average men, the hierarchy was mouth, eye, and nose (but the eye and mouth were not significantly distinguishable here).

Duration results: area by facial attractiveness, area by dental esthetics, and area by rater sex.

For dental esthetic level and area of the face ( Fig 5 ) at IOTN 1, the eye received significantly more visual attention than did the mouth and nose ( P <0.0001 and P = 0.0001, respectively). At IOTN 7, the mouth had significantly more visual attention than it did in IOTN 1 ( P = 0.0063), became significantly more than the nose ( P = 0.0002), and was statistically indistinguishable from the eye ( P = 0.4853). At IOTN 10, the mouth received significantly more visual attention than it did in IOTN 7 ( P <0.0001), as well as significantly exceeding the nose ( P <0.0001) and the eye ( P = 0.0001).

For rater sex by area of the face ( Fig 5 ), again a significant difference was shown for male and female raters giving more visual attention to the eyes over the nose ( P <0.0001 and P <0.0001, respectively), with women showing this preference to a greater degree. Additionally, male ( P <0.0001) and female ( P = 0.0001) raters also spent significantly more visual time on the mouth than the nose. Overall, the hierarchy was eye, mouth, and nose for both male and female raters.

Results

Density was the measure of the total number of fixations in an interest area, and duration was the total time in milliseconds that the observer spent viewing a given interest area. Reliability was assessed; an intraclass correlation coefficient less than 0.40 was poor, 0.40 to 0.59 was fair, 0.60 and 0.74 was good, and greater than 0.75 was excellent. Intrarater and interrater reliabilities were good and excellent in the areas of eye, nose, and mouth for both density and duration of fixations (0.6-0.91). For this reason, these were the areas included in the data analysis. The reliability for the areas of chin, ear, and other had poor reliability in either density or duration, and were eliminated from the data analysis.

For density, significant interactions were seen for the variables of model facial attractiveness and area of the face ( P <0.0004), dental esthetic level and area of the face ( P <0.0001), and area of the face and rater sex ( P = 0.0098). Additionally, the main effects of area of the face were also significant ( P <0.0001). For facial attractiveness by area of the face ( Fig 4 ) in men of average attractiveness, the mouth received significantly more visual attention than it did in the unattractive ( P = 0.0023) and attractive ( P <0.0478) men. In average men, the mouth exceeded both the eye and the nose ( P <0.0001). For unattractive and attractive men, the hierarchy for visual attention was the same: the greatest density at the eyes followed by the mouth and the nose. The eyes were significantly different from the nose in both cases ( P <0.0001).

Density results: area by facial attractiveness, area by dental esthetics, and area by rater sex.

For dental esthetic level and area of the face ( Fig 4 ), with no treatment need (IOTN 1), the eye received significantly more visual attention than did the mouth ( P <0.0001). For subjects with borderline dental esthetics (IOTN 7), the mouth had significantly more visual attention than it did for subjects in IOTN 1 ( P = 0.0014) and significantly more than the nose ( P = 0.0001), but it was not statistically distinguishable from the eye. At IOTN 10, the mouth received significantly more visual attention than it did in the borderline models (IOTN 7) ( P <0.0001), and it significantly exceeded the eye ( P <0.0001) and the nose ( P <0.0001).

For area of the face and rater sex ( Fig 4 ), both male and female raters gave significantly more visual attention to the eyes than the nose ( P <0.0007 and P = 0.0001, respectively). Women gave significantly more visual attention to the eyes than did the men ( P = 0.0226). Male raters showed significantly more visual attention to the mouth than the nose ( P = 0.0001).

For duration, the pattern was the same as for density. Significant interactions were found in the same areas: model facial attractiveness and area of the face ( P <0.0013), dental esthetic level and area of the face ( P <0.0001), and area of the face and rater sex ( P = 0.0087). Additionally, the main effects of dental esthetics (occlusion) and area of the face were significant ( P <0.0018 and P <0.0001, respectively).

For facial attractiveness by area of the face ( Fig 5 ), again significant differences were seen in duration, with men of average attractiveness receiving more visual attention to the mouth than the unattractive ( P = 0.0447) and attractive ( P <0.0030) models. Again, the hierarchy for unattractive and attractive men was eye, mouth, and nose, with the eye receiving significantly more visual attention than the nose ( P = 0.0001, unattractive; P <0.0001, attractive), but only more than the mouth for attractive men. For average men, the hierarchy was mouth, eye, and nose (but the eye and mouth were not significantly distinguishable here).

Duration results: area by facial attractiveness, area by dental esthetics, and area by rater sex.

For dental esthetic level and area of the face ( Fig 5 ) at IOTN 1, the eye received significantly more visual attention than did the mouth and nose ( P <0.0001 and P = 0.0001, respectively). At IOTN 7, the mouth had significantly more visual attention than it did in IOTN 1 ( P = 0.0063), became significantly more than the nose ( P = 0.0002), and was statistically indistinguishable from the eye ( P = 0.4853). At IOTN 10, the mouth received significantly more visual attention than it did in IOTN 7 ( P <0.0001), as well as significantly exceeding the nose ( P <0.0001) and the eye ( P = 0.0001).

For rater sex by area of the face ( Fig 5 ), again a significant difference was shown for male and female raters giving more visual attention to the eyes over the nose ( P <0.0001 and P <0.0001, respectively), with women showing this preference to a greater degree. Additionally, male ( P <0.0001) and female ( P = 0.0001) raters also spent significantly more visual time on the mouth than the nose. Overall, the hierarchy was eye, mouth, and nose for both male and female raters.

Discussion

The specific aim of this study was to determine whether there is a point on the IOTN-AC when the severity of dental esthetics would be enough to attract visual attention in men with varying background attractiveness levels. This was done in a manner that accounted for many potential confounding factors that have been identified in the literature. These include background facial attractiveness and sex of the model, sex and dental knowledge of the rater, and facial perspective.

Dental esthetic ratings were based on the IOTN-AC. This method has been tested for reliability and validity. It has received some criticism in its validity and usefulness in the evaluation of dental esthetics and subsequent classifications of treatment need. This is often due to its comparison with the dental health component, because IOTN-AC scores and dental health component scores can differ for the treatment need of a patient. For the purposes of this study, we were only evaluating the esthetic perceptions from a frontal view, and not using this to directly evaluate dental health treatment need. The IOTN-AC was the most reliable and valid tool to evaluate dental esthetic levels.

In this study, significant interactions were found between multiple independent variables in 2-way interactions. For area of the face by attractiveness in density and duration ( Figs 4 and 5 ) with attractive and unattractive models, the hierarchy of visual attention was as expected based on other studies with female models: eye, mouth, and nose. We found, however, that in average male models, visual attention to the mouth significantly exceeded that of the eye regardless of dental esthetics, which begin to provide evidence of differences between male and female models. In the study by Richards et al, visual attention to the mouth never significantly exceeded that to the eye in any female model. This raises the question as to why raters looked more to the mouth in average men. Interestingly, Chang et al also found, in a study looking at dental esthetic variables in the context of background facial attractiveness, differences in the perceptions for average models vs unattractive and attractive models.

The next area of consideration was area of the face by dental esthetic level. Here, the results for density and duration ( Figs 4 and 5 ) were initially similar to what has been shown with female models. As the dental attractiveness level decreased from no treatment need (IOTN 1) to borderline (IOTN 7), the visual attention to the mouth became significantly greater but did not exceed the eye. What is different in the male model is that at the definite treatment need level (IOTN 10), the visual attention to the mouth significantly exceeded that to the eye. This is true irrespective of background facial attractiveness. In women, this was not the case; mean visual attention to the mouth did not exceed that to the eye in density or duration at IOTN 10 (at any attractiveness level).

In the last 2-way interaction for male models of rater sex by area of the face, our results are consistent with others. The sex of the rater has an effect on dental esthetic ratings. It can be seen that in duration and density ( Figs 4 and 5 ), both men and women gave significantly greater visual attention to eyes over noses, but women showed this to a greater degree. Male raters had a significantly stronger preference in density and duration for the mouth over the nose, but female raters showed this only for duration. In density alone, women gave significantly more attention to the eyes than did men. One could argue that the difference in the numbers of male and female raters could affect these findings. Although an effort was made to balance them, it was not possible because of the consecutive volunteer nature of raters recruited for the study.

Because the sex of the model has an effect on dental esthetic preferences in the full-face perspective, the background facial attractiveness must be evaluated further. Interrater reliability in men was poor for facial attractiveness (weighted kappa, 0.35; 95% CI, 0.34-0.37). This shows that agreement between raters was not high. In women on the other hand, Richards et al reported better agreement for interrater reliability (weighted kappa, 0.51; 95% CI, 0.49-0.52). Attractiveness ratings in women were fairly consistent among raters. In men, however, we found less agreement between raters as to which man is or is not attractive.

In the eye-tracking studies with women, significant interactions were found for the 3-way interaction of facial attractiveness, by area, and by dental esthetics. The significant interactions here were found mostly among women with attractive facial esthetics. It was concluded that the disharmony between facial and dental esthetics (low dental esthetics and high facial esthetics) was the reason for the increased visual attention to the mouth in these attractive women. More attention is given to attractiveness in women, and it has been shown that it can be evaluated across many raters with more consistency. The 3-way interaction was not significant in men. The lack of agreement between raters on facial attractiveness may explain why this interaction was not found in men. Male attractiveness is simply less well defined, with the result that all men could benefit from treatment when the treatment need is definite.

In contrast to reliability for facial attractiveness, the reliability of the areas of the face was consistent with previous studies, with good-to-excellent reliability for the areas of eye, mouth, and nose. But reliability in men for density or duration at ear, chin, and other was poor and therefore not analyzed.

An earlier study implied that the benefits of orthodontic treatment are greater in men at lower levels of facial attractiveness. Those investigators concluded that a positive effect on facial attractiveness was observed in orthodontically treated men, especially those with lower initial facial attractiveness scores. A greater benefit was seen in men with lower facial attractiveness; this may imply that in men the attention to an unesthetic dentition is more pronounced, since it did not follow the disharmony in facial and dental esthetics as it did in women.

Kerosuo et al showed that with 3 grades of background facial attractiveness, as in our study, incisal disarrangement corresponded to a 1-step drop in the facial attractiveness of the model, compared with the same face with a normal occlusion. An argument could be made that the background attractiveness of the model was therefore modified in the experiment. Our results show that background attractiveness was not a factor in the increased visual attention to the most unesthetic dentition (IOTN 10), since this factor was not significant along with area of the face and dental esthetic level.

With recent increased awareness and concern over bullying in young children, new attention is on the influence of the dentition. In a 2011 article by Seehra at al, the complex relationships between malocclusion, bullying, self-esteem, and oral health-related quality of life were discussed. In 2013, Seehra et al took this a step farther by examining the effect of interceptive orthodontic treatment on the self-esteem and oral health-related quality of life in patients with a history of bullying. They showed that after the beginning of treatment, 78% were no longer being bullied. Although self-esteem was not greatly impacted, there was a significant improvement in oral health-related quality of life in children who were no longer being bullied. The need to further understand the complex relationship between dental esthetics and its impact psychologically and psychosocially on a person begins with an understanding of the visual attention to the dentition in an objective setting, as we have presented.

The objective of this study was to determine when deviations from esthetics with no treatment need to those with borderline treatment need to those with definite treatment need would be noticed by a lay peer observer unbiased toward looking at the mouth in men with different background facial attractiveness levels. We wanted to compare our results with male models to previous studies of similar methodology using female models. There are differences in the way in which the sexes look at the face of a man or a woman based on differing dental esthetics and background facial attractiveness. Attractiveness studies have shown that in general women are rated more critically, and previous eye-tracking studies have supported this notion in attractive women with unesthetic dentitions. We have presented evidence that raters are more able to agree on attractiveness in women than they are in men. This may be why the interactions of area, attractiveness, and dental esthetics were significant in attractive women but not in men. In men, the lowest dental esthetics (IOTN 10) were significantly noticed, and even to a greater degree than in women, but the background facial attractiveness “disharmony” does not appear to be the reason for the attention in men as it is in women. This study is only generalizable to men in the 1- to 30-year age range. Therefore, from the evidence presented here, treatment for the most unesthetic dentition could benefit men at all levels of background facial attractiveness.

Conclusions

• 1.

  Visual attention to the mouth was the greatest in men of average facial attractiveness, irrespective of dental esthetics.

• 2.

  In borderline dental esthetics (IOTN 7), the eye and the mouth were statistically indistinguishable, but in the most unesthetic dental attractiveness level (IOTN 10), the mouth exceeded the eye. The most unesthetic malocclusion does significantly attract and affect visual attention in men.

• 3.

  Male and female raters showed differences in their visual attention to faces of men.

• 4.

  Laypersons gave significant visual attention to poor dental esthetics in men, and this was irrespective of background attractiveness, which was counter to what was seen in women.

Discussion

The specific aim of this study was to determine whether there is a point on the IOTN-AC when the severity of dental esthetics would be enough to attract visual attention in men with varying background attractiveness levels. This was done in a manner that accounted for many potential confounding factors that have been identified in the literature. These include background facial attractiveness and sex of the model, sex and dental knowledge of the rater, and facial perspective.

Dental esthetic ratings were based on the IOTN-AC. This method has been tested for reliability and validity. It has received some criticism in its validity and usefulness in the evaluation of dental esthetics and subsequent classifications of treatment need. This is often due to its comparison with the dental health component, because IOTN-AC scores and dental health component scores can differ for the treatment need of a patient. For the purposes of this study, we were only evaluating the esthetic perceptions from a frontal view, and not using this to directly evaluate dental health treatment need. The IOTN-AC was the most reliable and valid tool to evaluate dental esthetic levels.

In this study, significant interactions were found between multiple independent variables in 2-way interactions. For area of the face by attractiveness in density and duration ( Figs 4 and 5 ) with attractive and unattractive models, the hierarchy of visual attention was as expected based on other studies with female models: eye, mouth, and nose. We found, however, that in average male models, visual attention to the mouth significantly exceeded that of the eye regardless of dental esthetics, which begin to provide evidence of differences between male and female models. In the study by Richards et al, visual attention to the mouth never significantly exceeded that to the eye in any female model. This raises the question as to why raters looked more to the mouth in average men. Interestingly, Chang et al also found, in a study looking at dental esthetic variables in the context of background facial attractiveness, differences in the perceptions for average models vs unattractive and attractive models.

The next area of consideration was area of the face by dental esthetic level. Here, the results for density and duration ( Figs 4 and 5 ) were initially similar to what has been shown with female models. As the dental attractiveness level decreased from no treatment need (IOTN 1) to borderline (IOTN 7), the visual attention to the mouth became significantly greater but did not exceed the eye. What is different in the male model is that at the definite treatment need level (IOTN 10), the visual attention to the mouth significantly exceeded that to the eye. This is true irrespective of background facial attractiveness. In women, this was not the case; mean visual attention to the mouth did not exceed that to the eye in density or duration at IOTN 10 (at any attractiveness level).

In the last 2-way interaction for male models of rater sex by area of the face, our results are consistent with others. The sex of the rater has an effect on dental esthetic ratings. It can be seen that in duration and density ( Figs 4 and 5 ), both men and women gave significantly greater visual attention to eyes over noses, but women showed this to a greater degree. Male raters had a significantly stronger preference in density and duration for the mouth over the nose, but female raters showed this only for duration. In density alone, women gave significantly more attention to the eyes than did men. One could argue that the difference in the numbers of male and female raters could affect these findings. Although an effort was made to balance them, it was not possible because of the consecutive volunteer nature of raters recruited for the study.

Because the sex of the model has an effect on dental esthetic preferences in the full-face perspective, the background facial attractiveness must be evaluated further. Interrater reliability in men was poor for facial attractiveness (weighted kappa, 0.35; 95% CI, 0.34-0.37). This shows that agreement between raters was not high. In women on the other hand, Richards et al reported better agreement for interrater reliability (weighted kappa, 0.51; 95% CI, 0.49-0.52). Attractiveness ratings in women were fairly consistent among raters. In men, however, we found less agreement between raters as to which man is or is not attractive.

In the eye-tracking studies with women, significant interactions were found for the 3-way interaction of facial attractiveness, by area, and by dental esthetics. The significant interactions here were found mostly among women with attractive facial esthetics. It was concluded that the disharmony between facial and dental esthetics (low dental esthetics and high facial esthetics) was the reason for the increased visual attention to the mouth in these attractive women. More attention is given to attractiveness in women, and it has been shown that it can be evaluated across many raters with more consistency. The 3-way interaction was not significant in men. The lack of agreement between raters on facial attractiveness may explain why this interaction was not found in men. Male attractiveness is simply less well defined, with the result that all men could benefit from treatment when the treatment need is definite.

In contrast to reliability for facial attractiveness, the reliability of the areas of the face was consistent with previous studies, with good-to-excellent reliability for the areas of eye, mouth, and nose. But reliability in men for density or duration at ear, chin, and other was poor and therefore not analyzed.

An earlier study implied that the benefits of orthodontic treatment are greater in men at lower levels of facial attractiveness. Those investigators concluded that a positive effect on facial attractiveness was observed in orthodontically treated men, especially those with lower initial facial attractiveness scores. A greater benefit was seen in men with lower facial attractiveness; this may imply that in men the attention to an unesthetic dentition is more pronounced, since it did not follow the disharmony in facial and dental esthetics as it did in women.

Kerosuo et al showed that with 3 grades of background facial attractiveness, as in our study, incisal disarrangement corresponded to a 1-step drop in the facial attractiveness of the model, compared with the same face with a normal occlusion. An argument could be made that the background attractiveness of the model was therefore modified in the experiment. Our results show that background attractiveness was not a factor in the increased visual attention to the most unesthetic dentition (IOTN 10), since this factor was not significant along with area of the face and dental esthetic level.

With recent increased awareness and concern over bullying in young children, new attention is on the influence of the dentition. In a 2011 article by Seehra at al, the complex relationships between malocclusion, bullying, self-esteem, and oral health-related quality of life were discussed. In 2013, Seehra et al took this a step farther by examining the effect of interceptive orthodontic treatment on the self-esteem and oral health-related quality of life in patients with a history of bullying. They showed that after the beginning of treatment, 78% were no longer being bullied. Although self-esteem was not greatly impacted, there was a significant improvement in oral health-related quality of life in children who were no longer being bullied. The need to further understand the complex relationship between dental esthetics and its impact psychologically and psychosocially on a person begins with an understanding of the visual attention to the dentition in an objective setting, as we have presented.

The objective of this study was to determine when deviations from esthetics with no treatment need to those with borderline treatment need to those with definite treatment need would be noticed by a lay peer observer unbiased toward looking at the mouth in men with different background facial attractiveness levels. We wanted to compare our results with male models to previous studies of similar methodology using female models. There are differences in the way in which the sexes look at the face of a man or a woman based on differing dental esthetics and background facial attractiveness. Attractiveness studies have shown that in general women are rated more critically, and previous eye-tracking studies have supported this notion in attractive women with unesthetic dentitions. We have presented evidence that raters are more able to agree on attractiveness in women than they are in men. This may be why the interactions of area, attractiveness, and dental esthetics were significant in attractive women but not in men. In men, the lowest dental esthetics (IOTN 10) were significantly noticed, and even to a greater degree than in women, but the background facial attractiveness “disharmony” does not appear to be the reason for the attention in men as it is in women. This study is only generalizable to men in the 1- to 30-year age range. Therefore, from the evidence presented here, treatment for the most unesthetic dentition could benefit men at all levels of background facial attractiveness.