The influence of incisor inclination and anterior vertical facial height on facial attractiveness in an Asian woman

Introduction

Orthodontic treatment can help improve facial attractiveness through the modification of factors affecting the soft tissue profile. The objectives of this study were to determine the impact of different maxillary incisal inclinations and lower anterior facial heights (at rest and with a smile) on the facial attractiveness of an Asian woman, as perceived by different panels of raters using visual analog scale (VAS) scores.

Methods

A cross-sectional study was performed with 66 raters equally divided into 3 panels that consisted of general dentists, orthodontic residents, and laypersons. Raters assessed modified photographs of a subject with various incisor inclinations and lower anterior facial height/total anterior facial height (LAFH/TAFH) on lateral profile view. Modifications were made using Photoshop software (Adobe, San Jose, Calif). Subjective evaluations of facial attractiveness were performed by raters using VAS. Kruskal-Wallis test was used to compare VAS scores among raters. Mann-Whitney U test was applied to compare VAS scores between groups.

Results

Significant differences in VAS scores were found among raters for −10° ( P = 0.004) and −15° ( P = 0.021) incisal inclinations. Significant differences were found in VAS scores for −8% LAFH/TAFH ( P = 0.044) and 4% LAFH/TAFH with smile ( P = 0.002).

Conclusions

Professionals preferred normal incisal inclinations to be the most attractive. General dentists found reduced facial height to be unattractive. Orthodontic residents and laypersons considered increased LAFH/TAFH to be most unattractive. Smile had a negative impact on VAS scores at extreme anterior facial height modifications.

Highlights

  • Normal cephalometric values can be used for esthetic guidelines.

  • Increased lower anterior facial heights were considered most unattractive.

  • Normal incisor inclination was preferred by all raters.

  • Gender had no influence on visual analog scale esthetic scores.

  • Smile had a negative impact on facial attractiveness on extreme modifications.

One of the important reasons patients seek orthodontic care is to improve their facial attractiveness. Technological advancements such as computer simulation software that predicts treatment outcomes help orthodontists develop customized treatment plans that best serve orthodontic patients. The results of treatment are considered to be successful when they satisfy the patients and the societal perceptions of beauty. Perception has been defined as the process by which patterns of environmental stimuli are organized and interpreted; it can be influenced by a variety of physical, physiological, and social factors. These perceptions are culturally or even religiously determined and are transmitted to the masses via different formats, such as the media, which has established esthetic standards and has had a direct effect on the social and personal preferences related to facial esthetics and smile pleasantness. , However, professional opinions sometimes do not coincide with the perceptions and expectations of laypersons.

Orthodontic treatment targets the dentition and the maxillomandibular relationships to create a considerable impact on facial esthetics. Facial harmony must be achieved in both the frontal and lateral aspects of the face. Orthodontic treatment that relies on cephalometrics to determine esthetic goals might not be able to produce the desired results. For example, the display of the maxillary dentition during rest and smiling is considered youthful and esthetically pleasing. Because the soft tissue esthetics of the face (lips, nose, and chin) depend on the underlying skeletal and dental support, an unfavorable change in the incisor position can lead to poor soft tissue outcome. This reflects the importance of incisor inclination on facial esthetics and should be a critical component of treatment planning. , The vertical dimension of the face is equally important for the orthodontist; controlling the vertical dimension is a predictor of treatment success. In growing patients, this vertical growth tendency can be managed via different extraoral or intraoral devices such as high pull headgears and high bite blocks. Surgical intervention is required for correction of severe vertical deformity in adults.

Ideal smile characteristics appreciated from the frontal view include an adequate incisal display and minimal buccal corridor display. However, incisor inclinations and facial heights can be best appreciated from the lateral profile view. The objectives of this study were to determine the impact of different maxillary incisal inclinations and lower anterior facial heights (at rest and with a smile) on the facial attractiveness of an adult Asian female as perceived by different panels of raters using visual analog scale (VAS) scores. The null hypothesis was that there is no impact of various incisal inclinations and lower anterior facial heights (at rest and with smile) on facial attractiveness as perceived by the different panels of raters.

Material and methods

A cross-sectional study was performed after obtaining ethical approval from the institutional ethical review board (no. 2019-1619-4175). The sample size was calculated by Open-Epi software using the findings of Ghaleb et al, who reported the mean VAS scores of 10° by orthodontists and laypersons to be 62.23 ± 13.62 and 49.99 ± 14.84, respectively. The power of the study was set at 80% with a confidence interval of 95%. It was calculated that at least 22 subjects were required in each group. Because we had 3 different panels of raters, the total sample size was 66. Three different panels of raters equally divided into general dentists (GD), orthodontic residents (OR), and laypersons (LP) evaluated a series of images that showed changes in incisal inclinations and vertical facial heights. Female subject aged 18 years, who signed the informed consent, was included in this study on the basis of the following inclusion criteria: a clinical examination showed an orthognatic profile with a pleasant smile in both frontal and profile views, lateral cephalometric examination showed a Class I skeletal base (ANB, 2 ± 2), maxillary incisor to sella-nasion angle (UI/SN, 102 ± 5) was well-positioned within the cephalometric standard range, lower anterior facial height/total anterior facial height (LAFH/TAFH) was 55% according to Eastman cephalometrics, and the subject had a Class I dental relationships with ideal overjet and overbite. The exclusion criteria were any craniofacial/dental anomaly or syndrome or a history of trauma or surgery involving facial structures.

The clinician helped the patient assume the natural head position (esthetic position) by a method recommended by Bass so that the face was not tilted up or down. This is an easy, reliable, and replicable way to obtain profile pictures in clinical practice. Two profile pictures were taken 1.5 meters away from the subject using a Nikon camera D3500 (24.2 million megapixels; Nikon, Tokyo, Japan) with the subjects’ head fixed in the natural head position. One photograph was in a normal resting posture with relaxed lips, and the other one was with a social smile that exposed the distal aspect of the canine. Photographs were modified using an image editing software (Adobe Photoshop CS [version 8.0; Adobe, San Jose, Calif] and Adobe Illustrator CS5 [version 15.0.1; Adobe]) according to the guidelines described by Ghaleb et al and Devanna for incisal inclinations alterations and angular measurements. To simulate the changes in incisor inclinations, the crowns of the central and lateral incisors were separately sliced using the editing software. Each tooth was considered as an individual object with the center of rotation at the incisal edge. The central incisor was superimposed from the tracing of the lateral cephalograms, and the center of rotation was placed at the incisal edge of the tooth. To maintain the symmetry, the center of rotation of the lateral incisor was set at the midpoint of the mesiodistal width. To maintain the vertical positions of the maxillary incisors, horizontal lines were drawn as tangents to the incisal edges of the teeth, and vertical tangents were drawn medial to the maxillary canines as the distal limit for sagittal repositioning of the lateral incisor. Seven final images were obtained for the female subjects (1 unaltered, 3 lingual, and 3 labial). This resulted in 4 categories according to the degree of proclination or retroclination (ie, normal, mild, moderate, and severe proclination and retroclination) ( Fig 1 ). Artistic touches were given when necessary to maintain the natural appearance of the face.

Fig 1
Normal incisor inclination and 6 modifications in labial and lingual directions, with changes in increments of 5°.

The esthetic horizontal line (Hr) was taken as a stable reference that is not altered by orthognathic or orthopedic treatment. The Sn-Pg′ line joins the subnasale point (the deepest point at the junction where the profile of the nose joins the upper lip) and the facial pogonion (the most prominent point on soft tissue chin). This represents the lower facial third (ie, nearest reference part of the face to the incisors) ( Fig 2 ).

Fig 2
Angular measurements for the incisor inclination modifications.

The following steps were carried out to obtain angular measurements: (1) drawing of the line Sn-Pg′ and Hr passing through the mid-third; (2) determining the most anterior point on the labial surface of the maxillary incisor (obtained by the intersection of this surface with the vertical tangent to the most labial aspect of the maxillary incisor); and (3) a tangent (Tg) passing through this point resulted in 2 angular measurements for each inclination: Tg/Hr is the angle formed between incisor inclination and esthetic horizontal, and Tg/Sn-Pg′ is the angle formed between incisor inclination and lower facial third. A positive value is given to the angle when the tangent is forward and a negative value when the tangent is backward.

The angular measurements for each of the modified incisal inclinations are given in Table I .

Table I
Angular measurements of incisor inclination of the face, for various inclinations
Photographs incisal inclinations, ° Angle Tg/Hr, ° Angle Tg/Sn-Pg′, °
−15 76.10 −9.23
−10 78.40 −7.80
−5 80.20 −6.45
0 85.40 −4.50
5 88.60 −2.20
10 99.70 13.50
15 113.00 26.41

Tg/Hr , the angle between incisor inclination and aesthetic horizontal; Tg/Sn-Pg′ , the angle between incisor inclination and lower facial third (positive value when the tangent is forward and negative value when the tangent is backward).

The anterior vertical dimension of the facial profile of the female subject was altered by stretching and depressing the image at the soft tissue points subnasale and sublabiale. The LAFH/TAFH ratio of 55% was increased and decreased by 4%. The modified LAFH/TAFH heights were 2 standard deviation away from the Eastman cephalometrics standard range (55% ± 2%). These alterations produced fewer pictures with appreciable differences in facial heights for the raters to score and judge accurately. The soft tissue contours above the columella and below the soft tissue pogonion were not altered and were identical for all images. The altered LAFH/TAFH generated 5 lateral profile images of the female subject (47%, 51%, 55%, 59%, and 63%) at rest and 5 lateral profile pictures on smiling, ( Figs 3 and 4 ) whereas the anteroposterior proportions were kept constant (Class I).

Fig 3
Normal LAFH/TAFH ratio at rest, and 4 modifications with 4% incremental increases (59% and 63%) and decreases (51% and 47%).

Fig 4
Normal LAFH/TAFH ratio with smile and 4 modifications with 4% incremental increases (59% and 63%) and decreases (51% and 47%).

The altered images were shown to the different panels of raters on a Powerpoint presentation. These raters provided esthetic scores for the profile on the basis of facial attractiveness using the VAS. This scale was created on a 100 mm interrupted line anchored at 0 on the left (very unattractive) and 10 on the right (very attractive). The following parameters were evaluated by the raters: (1) impact of different incisal inclinations on facial attractiveness, (2) impact of different vertical anterior facial heights without smile, and (3) impact of different vertical anterior facial heights with smile.

Intraexaminer reliability was assessed by incorporating a duplicate image of one of the altered profiles for each of the original test images. The raters were unaware of the duplicate image and were asked to score it as an additional image. VAS scores were compared by applying the intraclass correlation coefficient between both the original and duplicate pictures, which showed a good agreement (0.83).

Statistical analysis

Data analysis was performed using SPSS (version 19.0; SPSS, Chicago, Ill). Descriptive statistics (ie, mean and standard deviation) were calculated for the age of raters, and median and interquartile range were calculated for the VAS scores from each category of incisor inclinations and LAFH/TAFH altered groups. The normality of data was determined by applying the Shapiro-Wilk test, which yielded a nonnormal distribution. The Kruskal-Wallis test was used to determine statistically significant differences among panels of raters for various incisor inclinations and LAFH/TAFHs. To compare the VAS scores between groups of raters, the Mann-Whitney U test was applied. The level of significance was kept at P ≤ 0.05.

Results

The mean ages of the raters were 26.96 ± 2.08 years for OR, 30.59 ± ;6.39 years for GD, and 27.50 ± 6.82 years for LP, whereas the gender distributions for our raters were 8 males and 14 females (OR), 10 males and 12 females (GD), and 14 males and 8 females (LP).

Gender dimorphism within the raters is shown in Table II . Female raters preferred normal inclinations and found 15° to be displeasing. They found −4% LAFH/TAFH to be attractive and −8% to be the most unattractive at rest. With smile, they found normal LAFH/TAFH to be the most attractive profile and 8% to be the most unattractive.

Aug 14, 2021 | Posted by in Orthodontics | Comments Off on The influence of incisor inclination and anterior vertical facial height on facial attractiveness in an Asian woman
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