Ranking fluctuating asymmetry in a dot figure and the significant impact of imagining a face

The influence of nasal deviation on the perception of maxillary dental centreline and smile aesthetics

OBJECTIVE

To assess the impact of nasal deviation on the perception of the maxillary dental centreline position as judged by orthodontists, dentists and laypersons.

DESIGN

Cross-sectional study.

SETTING

Barts and the London School of Medicine and Dentistry, Queen Mary University of London, UK.

PARTICIPANTS

Three groups of raters comprising 30 orthodontists, 30 dentists and 30 laypersons.

METHODS

A frontal photograph of a smiling white woman was captured and digitally manipulated with varying degrees of nasal deviation and dental centreline (DC) position in increments of 1.5 mm and 3 mm to the right and left. Three rater groups assessed the attractiveness of images using a visual analogue scale (VAS). Multiple regression analysis was undertaken, and images were compared using the Tukey HSD method.

RESULTS

Using a mixed linear model, the intraclass correlation coefficient (ICC) was estimated in the range of 69%-86%, indicating good inter-rater reliability. The interaction between image rating and nasal position (P < 0.001), DC position (P < 0.001) and the relationship between nose and DC position (P < 0.001) were found to be statistically significant with symmetrical upper midline and nasal tip position, both considered to be most aesthetically pleasing. Image rating was not influenced by rater group type (P = 0.995), age (P = 0.983) or sex (P = 0.476).

CONCLUSION

There was a preference for a central and coincident nose and maxillary DC position uniformly across the rater groups. Deviations of the nose, DC and their interactions negatively impacted on perceived smile aesthetics with increasing extent and opposing direction of deviations rated progressively more unaesthetic. No differences were observed between orthodontists, general dental practitioners and lay people with respect to perceived impact on smile aesthetics.

A review of genetics of nasal development and morphological variation

The nose is central in the determination of facial esthetics. The variations in its structural characteristics greatly influence the ultimate dentoskeletal positioning at the end of an orthodontic therapy. A careful insight into its developmental etiology will greatly aid the health care professional in identifying patient's real concern about the facial appearance. This in turn will aid in the fabrication of a better treatment plan regarding the end placement goals for the teeth and jaws in all the three dimensions of space. However, this important structure is often missed as a part of the diagnostic and treatment planning regime owing to the lack of meticulous understanding of its developmental etiology by the orthodontists. The development of the nose in the embryo occurs in pre skeletal and skeletal phases by a well-coordinated and regulated interaction of multiple signaling cascades with the crucial importance of each factor in the entire mechanism. The five key factors, which control frontonasal development are sonic hedgehog (SHH), fibroblast growth factors (FGF), transforming growth factor β (TGFβ), wingless (WNT) proteins, and bone morphogenetic protein (BMP). The recent evidence suggests the association of various nasal dimensions and their related syndromes with multiple genes. The revelation of nasal genetic makeup in totality will aid in ascertaining the direction of growth, which will govern our orthodontic treatment results and will also act as a harbinger for potential genetic editing and tissue engineering. This article describes at length the morphological and genetic aspect of nasal growth and development in light of the gender and racial variability along with the emphasis on the importance of knowing these nasal features with regard to diagnosis and treatment planning in orthodontics.

Association of Dorsal Reduction and Tip Rotation With Social Perception

Importance

Social perception by laypersons of people who have undergone rhinoplasty primarily for cosmetic purposes has not been fully described.

Objective

To evaluate the social perception of patients who have undergone cosmetic rhinoplasty.

Design, Setting, and Participants

Preoperative images of 4 patients with dorsal hump and tip ptosis were selected using the Delphi method. Computer simulations of dorsal hump reduction and tip rotation, alone or in combination, were performed. Using the Qualtrics internet-based survey platform, laypersons blinded to the purpose of the study viewed randomized original and simulated images and estimated the age, approachability, perceived success, overall health, intelligence, and rated their attractiveness on a visual analog scale from 0 to 100.

Main Outcomes and Measures

Comparison of responses (mean [SD] score) for each of the 3 types of simulated image against the original image employing a pairwise comparison of means (Dunnett test).

Results

After excluding 27 (4%) invalid responses, a total of 813 respondents (593 women and 220 men) were included in the study. The mean (SD) age was 44.6 (16.2) years. A total of 628 (77%) respondents were white and the observed highest level of education was a bachelor's degree (193 [24%]) or having attended college but without a diploma (194 [24%]). A significant age reduction (31 [10] years; 95% CI, -2.5 to 0; P = .04) and an increase in approachability (64 [22]; 95% CI, 0.7-5.8; P = .009), attractiveness (60 [22]; 95% CI, 4.0-9.4; P < .001), and health (70 [19]; 95% CI, 0.7-5.2; P = .006) for the simulation involving hump reduction was observed. When combined simulation of dorsum and tip rotation were tested, only significant increases in attractiveness (60 [23]; 95% CI, 3.6-9.0; P < .001) and health (69 [19]; 95% CI, 0.1-4.6; P = .03) were seen. No significant association was found for any of the responses when the tip alone was rotated. The Wilks λ varied slightly below 1.0 showing significant P values (P < .05) for all variance and covariance (respondent particulars).

Conclusions and Relevance

Though rhinoplasty procedures for nasal cosmesis involving both the nasal dorsum and tip were perceived to make a person more attractive and healthier, these results suggest that manipulation of the dorsum is more strongly associated with perception of the nose.

Level of Evidence

NA.

Differences Among Deviations, Genders, and Observers in the Perception of Eye and Nose Asymmetry

PURPOSE

This study investigated the degree and range of recognition of canting of the interpupillary line and deviation of the nose, which were regarded as "normal," "acceptable," and "needing surgical correction," according to different observer groups.

MATERIALS AND METHODS

Four different groups (40 each for laypeople, dental students, general dentists, and orthodontists) rated 11 simulated asymmetric images with canted eyes and a deviated nose separately. The raters categorized each image as normal, socially "acceptable" and not requiring correction, or abnormal and would benefit from correction. Survival analysis was used to evaluate the scope of perception.

RESULTS

The degree of recognition for eye-canting and nose deviation was 2.31 and 2.92, respectively. Eye-canting and nose deviation had lower degrees of recognition in the clockwise direction (2.13°) and on the left side (2.65°), respectively. Women showed a lower degree of the "upper limit of the acceptable range" for canted eyes, and men showed a lower "degree of recognition" and "upper limit of the acceptable range" for a deviated nose. Orthodontists showed a larger upper limit of the acceptable range for eye-canting (P < .001).

CONCLUSIONS

The perceptions of asymmetry of canted eyes and deviated nose were affected by gender, direction of asymmetry, and observer groups.

Medidas faciais em indivíduos adultos sem queixas orofaciais: compatibilidade entre medidas antropométricas e percepção facial

OBJETIVO: verificar a compatibilidade entre os achados de medidas faciais mensuradas pelo paquímetro e a percepção das características faciais realizada subjetivamente por um avaliador experiente. MÉTODOS: foram avaliados 24 sujeitos do sexo feminino e 24 do sexo masculino, pareados por sexo e idade, sem queixas morfológicas e funcionais do sistema estomatognático. Foram avaliados os aspectos de simetria entre os terços médio e inferior, altura e largura da face, e canto externo dos olhos direito e esquerdo às comissuras do lábio direita e esquerda, respectivamente. Cada medida foi realizada três vezes por paquímetro digital para consideração da média entre estes valores, considerando-se assimétricas comparações com diferenças superiores à 4 milímetros. A largura da face foi obtida por meio do paquímetro digital adaptado com prolongamento de 10 centímetros. Já a avaliação da percepção das características faciais foi realizada por um avaliador cegado quanto às medidas obtidas, devendo assinalar simetrias e assimetrias nestes mesmos aspectos avaliativos. RESULTADOS: por meio do teste de concordância de Kappa e Qui-quadrado, pode-se verificar uma boa compatibilidade entre as avaliações realizadas, demonstrando-se a fidedignidade entre os métodos utilizados. Além disso, verificou-se que existe uma relação entre a simetria dos terços da face e a atribuição da tipologia facial na avaliação perceptiva, observando-se simetria em faces médias e curtas e ausência de um padrão determinante para faces longas. CONCLUSÃO: a caracterização da simetria facial por paquímetro apresenta uma boa compatibilidade com a percepção subjetiva de um avaliador experiente.

The spectacular human nose: an amplifier of individual quality?

Amplifiers are signals that improve the perception of underlying differences in quality. They are cost free and advantageous to high quality individuals, but disadvantageous to low quality individuals, as poor quality is easier perceived because of the amplifier. For an amplifier to evolve, the average fitness benefit to the high quality individuals should be higher than the average cost for the low quality individuals. The human nose is, compared to the nose of most other primates, extraordinary large, fragile and easily broken—especially in male–male interactions. May it have evolved as an amplifier among high quality individuals, allowing easy assessment of individual quality and influencing the perception of attractiveness? We tested the latter by manipulating the position of the nose tip or, as a control, the mouth in facial pictures and had the pictures rated for attractiveness. Our results show that facial attractiveness failed to be influenced by mouth manipulations. Yet, facial attractiveness increased when the nose tip was artificially centered according to other facial features. Conversely, attractiveness decreased when the nose tip was displaced away from its central position. Our results suggest that our evaluation of attractiveness is clearly sensitive to the centering of the nose tip, possibly because it affects our perception of the face’s symmetry and/or averageness. However, whether such centering is related to individual quality remains unclear.