Facial esthetics in adolescents
A scientific essay in Medical Sciences
DOCTORAL THESIS defended in public on 14th of February 2008
In chapter 1 the topic of facial aesthetics is introduced. Although facial beauty might be subjective and “in the eyes of the beholder”, people agree on who is beautiful and who is not. Being beautiful is an advantage in real-live situations and is found to be as important for children and adults and for males as for females. Attractive individuals are not only judged and treated more positively, they also behave differently than unattractive ones. In this chapter subjects, panels, and measurement technique, used in the present study are described. Facial features, as objective parameters (overjet, ANB angle, Sn-GoGn angle, AC/IOTN), Angle Class, ‘golden’ ratios and ‘ideal’ proportions and angles and their relation to facial aesthetics in adolescents are introduced. The aims of this investigation and an overview of the study are presented.
In chapter 2 a new measuring system to judge facial aesthetics in young Caucasians is presented. The system uses sets of three photographs (one frontal, one three-quarter smiling, and one lateral) as a stimulus. Scores are performed on a visual analogue scale (VAS) with separate sets of reference photographs for girls and boys. The choice of the reference sets was based on a panel evaluation of facial aesthetics of 40 boys and 40 girls. A male and a female set of photographs with an average aesthetic score close to the median VAS score were selected. Reproducibility of the new measuring system was tested on a series of photographic sets of 64 patients, using a panel of 78 adult laymen and 89 professionals. The panel members assessed these sets of photographs on a VAS, in relation to the reference sets. The system was shown to be reproducible. Although the intra-observer reproducibility was low, the reliability coefficient was excellent (Cronbach’s alpha ≥ 0.98). Validity was tested by comparing the scores on the new scale with those of the three-quarter smiling photographic views on an earlier published scale by Peerlings. The correlation between the ratings on the new measuring system and the earlier published scale was 0.82 for the laymen and 0.77 for the professionals. The new system is simple and flexible in its use, and reproducible and valid for assessing facial aesthetics in young Caucasians. The system can be used in further investigations on the evaluation of facial aesthetics.
The objective of the study described in chapter 3 was to evaluate the influence of professional background, age, gender, and geographical region of panel members on their evaluation of the facial aesthetics of adolescents, and to assess the optimal panel size for epidemiological studies on facial aesthetics. A panel of 76 adult laymen from two different regions (Belgium and The Netherlands) and a panel of 89 orthodontists, from the same two regions, evaluated photographic sets of 64 adolescents (32 boys, 32 girls) on a VAS in relation to a reference set of photographs. The effects of the characteristics of the panel members on the VAS scores for boys and girls separately, as well as their interactions, were evaluated by multilevel models. These multilevel models revealed that laymen rated adolescents as more attractive than orthodontists. This finding was significant for all laymen, except for older males, and Belgian laymen, when rating girls. Older panel members rated boys significantly more attractive than younger panel members. Males rated adolescents more attractive than females. The latter was significant for all male subgroups, except for the lay male subgroup. There were regional differences. Based on the intraclass correlation coefficient, a panel of seven randomly selected laymen and/or orthodontists is sufficient to obtain reliable results in the aesthetic evaluation of adolescent faces, using photographs and a VAS.
The aim of the study described in chapter 4 was to evaluate the influence of characteristics of panel members, the effects of gender and Angle Class of adolescent patients on their change in facial aesthetics following orthodontic treatment, and to assess the optimal panel size for epidemiological studies on change in facial aesthetics after orthodontic treatment. A panel of 74 adult laymen and a panel of 87 orthodontists evaluated post-treatment photographic sets of 64 adolescent orthodontic patients in relation to the pre-treatment sets of the same patient on a 5-point scale. The main effects of professional background, age, gender, and geographical region of the panel members on the aesthetic scores, as well as their first order interactions were evaluated by multilevel models. Professional background, age, gender, and geographical region of panel members had an influence on the evaluation of the change of facial aesthetics following orthodontic treatment. The effect of gender and Angle Class of the patients on the scores was evaluated by two-way ANOVA. There was no difference in the mean scores for boys and girls. Improvement of facial aesthetics by orthodontic treatment was significant for Class I, Class II division 1, and Class II division 2 patients, but not for Class III patients. Based on the intraclass correlation coefficient (ICC), a panel of nine randomly selected orthodontists, a panel of 14 randomly selected laymen, or a mixed panel of 13 individuals is sufficient to obtain reliable results in the aesthetic evaluation of adolescent faces, using photographs and a 5-point scale.
The objective of the study described in chapter 5 was to examine the contribution of objective measures, representing anterior-posterior and vertical characteristics, dental aesthetics, or their combination that are used in daily orthodontic practice in the assessment of facial aesthetics. A panel of 78 laymen evaluated facial aesthetics of 32 boys and 32 girls, stratified over the four Angle Classes, on a VAS. The relation between the objective parameters and facial aesthetics was evaluated by backward multiple regression analysis. Dental aesthetics as expressed by the Aesthetic Component of the Index of Orthodontic Treatment Need (AC/IOTN) appeared to be the most important indicator for facial aesthetics. A new parameter, the “horizontal sum” was found to be a reliable variable for the anterior-posterior characteristics of the patient. Addition of this newly defined parameter to the AC/IOTN improves the prognostic value from 25% to 31%.
In chapter 6 a study is described in which the putative relation between facial aesthetics and golden proportions in Caucasian adolescents is tested. Adult laymen (N=76) evaluated sets of photographs of 64 adolescents on a VAS. The facial aesthetic value of each patient was calculated as a mean VAS score. Three observers recorded the position of 13 landmarks included in the putative golden proportions. Nineteen proportions, based on the golden proportions as defined by Ricketts, were determined, and the deviation of each proportion from the golden target (1.618) was calculated. The deviation was related to the VAS scores. Only four out of the 19 Pearson correlations between the deviation of the golden target and the VAS scores pointed into the proper direction, and were significant. Together, these variables explain only 16 % of the variance.
Chapter 7 reports on the study in which the hypothesis is tested that facial attractiveness in adolescents is related to ideal angles and ratios as indicated in the literature. Adult lay people (N=76) evaluated sets of photographs of 64 adolescents on a VAS. The facial esthetic value of each individual was calculated as a mean VAS score. Three observers recorded the position of 61 landmarks. Out of these, 45 landmarks with an acceptable reproducibility were found. Twenty-seven ideal ratios on frontal, and twenty-six ideal angles on lateral photographs, dealing with the accepted landmarks were found in the literature. These ratios and angles were calculated on the individual photographs as well as their deviation from the ideal target from literature. This deviation was related to the VAS scores. Two ratios and three angles had a significant negative correlation with the VAS scores, indicating that beautiful faces showed less deviation from the ideal target than less beautiful faces. Together, these variables explain 28.7% of the variance.
In chapter 8 a general discussion is given on the study as a whole and suggestions are made for further research.