Assessing the influence of asymmeftry affecting the mandible and chin point on perceived attractiveness in the orthognathic patient, clinician, and layperson

Determining the Degree of Perceptible Static Eyelid Asymmetry and Effect of Face Inversion: A Cross-sectional Pilot Study

PURPOSE

To determine the degree of static eyelid asymmetry required to be perceptible and whether this is affected by image inversion.

METHODS

Images of 3 volunteers were digitally manipulated to have eyelid asymmetry of 0.5 mm, 1 mm, or 1.5 mm of 3 different types, upper lid ptosis, upper lid retraction, and lower lid retraction. Forty-nine laypersons stated whether the images were symmetrical or asymmetrical. A separate inversion survey, completed by 29 clinicians, consisted of symmetrical images and 1 mm asymmetrical images, with half being inverted.

RESULTS

Upper lid ptosis, upper lid retraction, and lower lid retraction were not detected by most laypeople at 0.5 mm of severity (18.9%, 6.7%, 18.9% detection, respectively) but all 3 were detected by the majority of participants once asymmetry reached 1 mm severity (65.7%, 61.8%, 51.0% detection, respectively) and rose to over 70% identification at 1.5 mm (92.2%, 73.5%, 73.5% detection, respectively). Inversion of the images led to 19.7% lower rates of correct identification of asymmetrical faces compared with images presented in the correct orientation (80.7% asymmetry identified in normal images, 61.0% inverted, p < 0.001).

CONCLUSIONS

All asymmetries were detectable by a majority of laypersons at a severity of 1 mm. Image inversion decreases a clinician's ability to detect a 1 mm asymmetry, indicating an impaired asymmetry perception in the intraoperative view. This study provides research to counsel patients with varying degrees of eyelid asymmetry.

What is the Minimal Perceptible Change for the Dimensional Alteration of Facial Structures in the Frontal View?

BACKGROUND

A better understanding of the perceptibility of dimensional changes in facial structures is of interest to all involved in facial esthetics.

PURPOSE

We aimed to determine the minimal perceptible change (MPC) in the dimensional alterations of the facial structures in the frontal view and the influential factors.

STUDY DESIGN, SETTING, SAMPLE

This cross-sectional study was conducted on individuals accompanying the patients at the outpatient department of a tertiary-care hospital and students in art and science. Those with impaired cognition, craniofacial anomalies, history of esthetic facial surgeries and health professionals working on facial esthetics were excluded.

INDEPENDENT VARIABLE

The observers assessed the frontal photographs of 2 models and their modifications. The independent variables were the anatomic structure modified (mouth, nose, ears, eyes), the percentage change (5, 10, 15%), and the type of modification (magnification or reduction).

MAIN OUTCOME VARIABLES

The outcome variables were the MPC (perceived by at least 50% of the observers) and the perceptibility of changes (Yes/No) COVARIATES: The age of the observer, the sex of the observer and the model were the covariates.

ANALYSES

The intergroup differences in perceptibility of changes and the influence of independent variables and covariates were analyzed with χ2/Cochran's Q test and generalized estimating equations, respectively, with statistical significance set at P < .05.

RESULTS

The sample comprised 110 males and 110 females, aged 23.9 ± 5.8 years. The MPC was 5% for the mouth, nose, and eyes and 15% for the ears. The changes in the nose [OR = 0.68 (0.56 to 0.83), P < .001], ears [OR = 0.29 (0.24 to 0.36), P < .001], and eyes [OR = 0.78 (0.64 to 0.95), P = .015] were less perceptible than the mouth. The perceptibility was higher in female than male observers [OR = 1.37 (1.11 to 1.69), P = .003] and reduction than magnification [OR = 1.11 (1.00 to 1.23) P = .036]. Compared to a 5% change, the perceptibility was higher for 10 and 15% [OR = 2.00 (1.76 to 2.27), 3.33 (2.84 to 3.91), respectively, P < .001].

CONCLUSION AND RELEVANCE

The MPC was 5% for the mouth, nose, and eyes and 15% for the ears. The perceptibility of change was influenced by the structure, the extent and type of modification and the observer's sex. These findings may be of use to all professionals involved in esthetic facial corrections.

Cross-Sectional Study on Self-Perception of Dento-Facial Asymmetry

Background and Objectives: Facial symmetry is a key component of facial beauty and attractiveness. However, perfect symmetry is rare, and slight asymmetries, also known as natural asymmetries, are common and contribute to the uniqueness of each face. The perception of facial asymmetry varies among individuals and can be influenced by several factors. This study aimed to investigate the self-perception of dento-facial asymmetry among a sample of Romanian individuals, focusing on their awareness, the extent to which it bothers them, and their desire for correction. Materials and Methods: A cross-sectional analytical study was conducted with 283 participants from Romania between January and February 2024. Participants completed a questionnaire designed to assess their self-perception of facial asymmetry and socio-demographic characteristics. The questionnaire included 10 questions on self-perception of facial asymmetry and 8 questions on socio-demographic data. Statistical analysis was performed using SPSS 26.0, and the Pearson Chi-square test was used for comparative analysis. Results: The sample was predominantly female (75.3%) with an average age of 32.24 years. Most participants were from urban areas (80.6%) and had university degrees (58.7%). About 28.7% of participants observed facial asymmetry, with dental asymmetry being the most frequently reported, followed by asymmetries in the eyebrows and eyelids. The right side of the face was more commonly perceived as asymmetric. Although 24.4% of participants were bothered by their asymmetry, 39.2% expressed a desire to correct it. Conclusions: One-third of participants identified dento-facial asymmetry, with the dental level being the most reported. A significant portion of participants expressed a desire to correct their asymmetries, highlighting the importance of understanding self-perception in the context of facial aesthetics. This study underscores the subjective nature of facial asymmetry perception and the varying thresholds for what is considered bothersome or in need of correction.

Soft tissue movements after mandibular reconstruction using the vascularized iliac flap: patterns and predictions

OBJECTIVES

To investigate soft-to-hard tissue response following mandibular reconstruction and to develop a predictive model for projecting soft tissue movement.

MATERIALS AND METHODS

In this retrospective study, 18 patients receiving mandibular reconstruction using a vascularized iliac flap were enrolled. Various indicators for characterizing the movement of tissues were considered to identify the effective predictors for projecting soft tissue movements. Face-region-specific linear regression models for prediction were constructed and evaluated.

RESULTS

The arithmetic mean of hard tissue movement in an extended area had the strongest correlation with the movement of the focal soft tissue, while the arithmetic mean in a regional area (Ram) was a more effective predictor. The linear regression model using Ram, global extrema and distances between them as the predictors performed the best in the lower margin of the face, with an average error of 1.51 ± 1.38 mm. Soft tissue movement in the alveolar process was not correlated with the existence of dentition, only can be predicted by the soft tissue movement below it. The area of the masseter was strongly correlation with Ram, but no other factors.

CONCLUSIONS

An accurate prediction of soft tissue movements in the lower margin and the alveolar process of the face can be achieved by considering hard tissue and adjacent soft tissue movements. No effective predictor in the masseter area was identified.

CLINICAL RELEVANCE

We investigated the relationship between hard tissue movements and the soft tissue responses in the facial area. Through building predictive models for projecting postoperative soft tissue movements, we derive insights for the aesthetic outcome of face surgeries.

CLINICAL TRIAL REGISTRATION

This study was registered on the Chinese Clinical Trial Registry (registration number: ChiCTR2100054103).

The Influence of the Hourglass Form of the Neck on Perceptions of Frontal Esthetics

The purpose of this investigation was to evaluate the effect of the neck concavity angle (NCA) on different occupational groups' perceptions of frontal esthetics. An online survey was developed using Google Forms and sent to the observers through WhatsApp. Male and female frontal silhouettes were created, and NCAs that comprise the hourglass form of the neck were altered in 5 degrees increments from 120 degrees to 170 degrees. Observers were asked to score the images using 0 to 10 numerical rating scale. In all, 279 observers (97 orthodontists, 92 oral-maxillofacial surgeons, and 90 laypeople) participated in this study. For the male and female silhouettes, an NCA of 145 degrees was perceived as the most esthetic, while an NCA of 170 degrees was perceived as the least esthetic by all groups. Generally, an NCA greater than 145 degrees was perceived as less esthetic than an NCA smaller than 145 degrees. There was no significant difference between the scores of the observer groups for the silhouettes except for the female silhouettes with an NCA of 125 degrees or 150 degrees and the male silhouettes with an NCA of 145 degrees or 150 degrees. For both the female and male silhouettes, the further the NCA increased or decreased from 145 degrees, the less esthetic it was perceived to be. A significant increase in NCA was perceived as less esthetic than a significant decrease. The range of NCAs perceived as esthetic varied between 120 degrees and 145 degrees for women and between 130 degrees and 150 degrees for men. These ranges of variability of NCA may provide clinicians with useful information for orthognathic surgical planning.

Subjective evaluation of facial asymmetry with three-dimensional simulated images among the orthodontists and laypersons: a cross-sectional study

OBJECTIVES

We used three-dimensional (3D) virtual images to undertake a subjective evaluation of how different factors affect the perception of facial asymmetry among orthodontists and laypersons with the aim of providing a quantitative reference for clinics.

MATERIALS AND METHODS

A 3D virtual symmetrical facial image was acquired using FaceGen Modeller software. The left chin, mandible, lip and cheek of the virtual face were simulated in the horizontal (interior/exterior), vertical (up/down), or sagittal (forward or backward) direction in 3, 5, and 7 mm respectively with Maya software to increase asymmetry for the further subjective evaluation. A pilot study was performed among ten volunteers and 30 subjects of each group were expected to be included based on 80% sensitivity in this study. The sample size was increased by 60% to exclude incomplete and unqualified questionnaires. Eventually, a total of 48 orthodontists and 40 laypersons evaluated these images with a 10-point visual analog scale (VAS). The images were presented in random order. Each image would stop for 30 s for observers with a two-second interval between images. Asymmetry ratings and recognition accuracy for asymmetric virtual faces were analyzed to explore how different factors affect the subjective evaluation of facial asymmetry. Multivariate linear regression and multivariate logistic regression models were used for statistical data analysis.

RESULTS

Orthodontists were found to be more critical of asymmetry than laypersons. Our results showed that observers progressively decreased ratings by 1.219 on the VAS scale and increased recognition rates by 2.301-fold as the degree of asymmetry increased by 2 mm; asymmetry in the sagittal direction was the least noticeable compared with the horizontal and vertical directions; and chin asymmetry turned out to be the most sensitive part among the four parts we simulated. Mandible asymmetry was easily confused with cheek asymmetry in the horizontal direction.

CONCLUSIONS

The degree, types and parts of asymmetry can affect ratings for facial deformity as well as the accuracy rate of identifying the asymmetrical part. Although orthodontists have higher accuracy in diagnosing asymmetrical faces than laypersons, they fail to correctly distinguish some specific asymmetrical areas.

Is Beauty a Matter of Volume Distribution? Proposal of a New Aesthetic Three-Dimensional Guide in Orthognathic Surgery

BACKGROUND

Orthognathic surgery is a multidisciplinary surgery in which the aesthetic results have become increasingly important, and consequently, also the predictability of the surgical outcomes. In this paper, we analyzed the volumetric distribution of the lower two-thirds of the face, in patients operated by orthognathic surgery and selected for their attractiveness. Our goal was to analyze the aesthetic volumetric distribution for gender and to propose our operating philosophy, that a normative distribution of facial volumes could be used like a new 3D aesthetic guide in orthognathic planning.

METHODS

A group of 46 orthognathic patients (26 females, 20 males) with the best postoperative aesthetic score was selected by a jury of plastic surgeons, orthodontists, and journalists. The mean soft tissue volumes of the malar, maxillary, mandibular, and chin regions were analyzed.

RESULTS

Overall, we measured a mean female facial volume distribution of 38.7%, 29%, 27.6%, and 4.7%, respectively, in the malar, maxillary, mandibular, and chin regions, while in males, it was 37%, 26%, 30%, and 6%, respectively.

CONCLUSIONS

In this paper, the expansion of facial volumes in orthognathic surgery is proposed as a key point for facial harmonization. Beauty could be scientifically interpreted as a balanced distribution of facial volumes, and the virtual study of this distribution can become an important part of the preoperative analysis, such as a "volumetric" 3D cephalometry, where the surgeon could use average values of aesthetic volumetric distribution as preoperative surgical references.

Comparison of Mandibular Volume and Linear Measurements in Patients with Mandibular Asymmetry

In patients with mandibular asymmetry, the volume of the mandible divided by the mandibular median plane is significantly larger on the non-deviated (N-Dev) side than on the deviated (Dev) side. However, it has been reported that there is no significant difference between the volumes of the N-Dev and Dev sides when the mandibular ramus and body are divided. The purpose of this study was to investigate which region is responsible for the volume difference between the N-Dev and Dev sides. Cone Beam Computed Tomography (CBCT) images of patients with mandibular asymmetry were analyzed by measuring the volume, and linear analysis of the mandibular body, ramus, and condyle on the N-Dev and Dev side was performed. In this study, CBCT images of 37 patients (8 Japanese, 16 Korean, and 13 Egyptian) aged ≥ 18 years with mandibular asymmetry (men: 20, women: 17) were used to evaluate mandibular asymmetry. In patients with mandibular asymmetry, the N-Dev side showed significantly larger values than the Dev side for both volume and linear condyle, ramus, and mandibular body measurements. These results do not differ according to sex or ethnicity. Therefore, it is suggested that the N-Dev side of mandibular asymmetry is large without any regional specificity in pathophysiology.

What do black patients expect from orthodontic treatment? The aesthetic perception of facial profile between orthodontists and black laypersons

Objective:

To evaluate the influence of anteroposterior position of the soft tissue on facial attractiveness in black people, and compare the perception of aesthetics and satisfaction between orthodontists and black laypersons.

Methods:

The sample was composed of 69 orthodontists and 69 laypersons of black ethnicity (n=138). Facial profile photographs of two black volunteers, a man and a woman, were digitally manipulated to change the position of the lips and chin, by making gradual changes of 4mm in relation to the true vertical line, simulating advance or retrusion of the soft tissues by -2, -6, -10, +2, +6, +10mm, totalling six images per sex. The photographs were classified by the research participants using a visual analogue scale (VAS), from 0 (unpleasant) to 100 (pleasant). The results were analyzed by generalized linear model and by the Fisher’s exact test, considering the level of significance of 5%.

Results:

The orthodontists and black laypersons considered straight profiles the most pleasant. The two groups classified the male profile as being more unpleasant in comparison with the female facial profile, which was concave. When evaluating all the images together, the image most indicated as being the most pleasant, once again, was the one with the straight profile, for both sexes.

Conclusion:

The influence of orthodontists’ and laypersons’ aesthetic perception on evaluating the facial profile of blacks was similar. The straight profile was classified as the most pleasant and the concave, as the most unpleasant.

Performance of Artificial Intelligence Models Designed for Diagnosis, Treatment Planning and Predicting Prognosis of Orthognathic Surgery (OGS)—A Scoping Review

The technological advancements in the field of medical science have led to an escalation in the development of artificial intelligence (AI) applications, which are being extensively used in health sciences. This scoping review aims to outline the application and performance of artificial intelligence models used for diagnosing, treatment planning and predicting the prognosis of orthognathic surgery (OGS). Data for this paper was searched through renowned electronic databases such as PubMed, Google Scholar, Scopus, Web of science, Embase and Cochrane for articles related to the research topic that have been published between January 2000 and February 2022. Eighteen articles that met the eligibility criteria were critically analyzed based on QUADAS-2 guidelines and the certainty of evidence of the included studies was assessed using the GRADE approach. AI has been applied for predicting the post-operative facial profiles and facial symmetry, deciding on the need for OGS, predicting perioperative blood loss, planning OGS, segmentation of maxillofacial structures for OGS, and differential diagnosis of OGS. AI models have proven to be efficient and have outperformed the conventional methods. These models are reported to be reliable and reproducible, hence they can be very useful for less experienced practitioners in clinical decision making and in achieving better clinical outcomes.

One-Half Wedge Osteotomy Genioplasty for Correction of Chin Deviation Based on Three-Dimensional Computed Tomography Measurements and Simulation

ABSTRACT

Conventional operations correcting chin deviations mainly rely on the observation and experience of the surgeons during the operation. We have created a new surgical method, one-half wedge osteotomy genioplasty (1/2WOG), that combines three-dimensional computed tomography measurements and simulation. This study evaluated the clinical effect of chin deviation correction with the 1/2WOG method. A total of 38 patients (15 men and 23 women) who underwent 1/2WOG between October 2019 and October 2014 were evaluated. The chin deviation angle and distance, and partial chin deformity were measured preoperatively using three-dimensional computed tomography data. Precise calculations and osteotomy lines were achieved by preoperative simulation. All patients underwent the same surgery by the same surgical team. The clinical effect of 1/2WOG was evaluated according to the preoperative and postoperative data and patient satisfaction. All 38 patients achieved satisfactory aesthetic results without major complications such as chin nerve injury or bone nonunion. Eight patients occured numbness of the lower lip after surgery; at 6-month follow-up, the numbness was reduced in 2 patients and disappeared in 6 patients. Compared with preoperative data, the chin deviation angle, chin deviation distance, and gonion-menton difference were significantly reduced postoperatively. During the 12-month follow-up, the patient satisfaction rate reached 90%. We conclude that chin deviation can be improved by 1/2WOG. The combination of digital technology measurements and simulation can increase the accuracy of the osteotomy line design, thus reducing surgical trauma and increasing patient satisfaction, which is worthy of clinical promotion.

The Perception of the Severity of Facial Asymmetry among Laypersons, General Practitioners, Orthodontists, and Maxillofacial Surgeons

STATEMENT OF THE PROBLEM

The degree of asymmetry perception of dental and medical practitioners is influenced by several factors. The perceived asymmetry affect the treatment plan design.

PURPOSE

The aim of the present study was to investigate the consistency of facial asymmetry and identify the amounts of transverse asymmetry that can be regarded as normal and might need correction.

MATERIALS AND METHOD

In this cross-sectional descriptive study, three-dimensional (3D) images of a man and a women volunteer were obtained. Then transverse changes were applied by ZBrush software so that for each volunteer, seven 3D images of their face with varying degrees of facial transverse asymmetry were created. Then, the images were displayed to four groups of observers including layperson, general dentists, orthodontists, and maxillofacial surgeons. Finally, the consistency of the perception of these four groups of observers with the different degrees of facial asymmetry was compared.

RESULTS

Fourteen photographic samples were evaluated and ranked by 80 observers in four groups. The consistency of the perception of the facial transverse asymmetry was equal to 33%, which indicated a lack of consistency.

CONCLUSION

According to the findings of this study, there was no consistency between the groups. The perception of dental professionals and ordinary people regarding the severity of transverse facial asymmetry seems to be inconsistent.

Asymmetric faces: Symbolic, spiritual, and representative

In humans, physically attractive faces are measurably, though subtly, asymmetric. As asymmetry increases, it has a negative impact. Medically, asymmetry can be congenital or acquired. Symbolically, it has varied connotations from playfulness and complexity to despair and corruption. In Chinese opera, stylized make-up exaggerates the features, and aspects of the "mask" indicate qualities of the character. The asymmetric faces belong to characters who are corrupt, devious, or evil. In the Dan culture of western Africa, performance masks channel spirits in the community. A spirit with asymmetric facial mask exemplifies ugliness and moral failing. The Nasca culture of South America made generic figures of farmers, deities, and so on, but not of individuals. However, there is evidence of mutual influence between the Nasca and the Wari, with whom they traded. A clay figure apparently representing an individual, or at least a very specific recognized persona, is a ball player with facial asymmetry presumably due to injury. Here the message is one of fierceness and strength. The relative rarity of asymmetric facial depictions compared to symmetric ones is cross-cultural. This implies that asymmetry is special somehow, in all connotations of that term.

Three-dimensional changes in the location of soft tissue landmarks following bimaxillary orthognathic surgery

OBJECTIVES

We sought to determine the amount of three-dimensional (3D) movement of soft tissue landmarks in patients who underwent bimaxillary orthognathic surgery.

MATERIALS AND METHODS

We recruited 28 patients (11 women and 17 men), who had received one-piece Le Fort I osteotomy with maxillary advancement and impaction, and bilateral sagittal split ramus osteotomy for mandibular setback. The 3D images were acquired 1-7 days before surgery and at least 6 months after surgery using stereophotogrammetry. We recorded 50 coordinate measurements and correlated the movements between soft and hard tissues. Paired samples t‑test, independent samples t‑test, and Pearson's correlation analysis were used for statistical analysis.

RESULTS

Patients' ages ranged from 17-31 years (mean 20.4 ± 3.0 years). The mean advancement and impaction of the maxilla was 4.7 ± 1.2 and 2.2 ± 1.0 mm, respectively. The mean setback of the mandible was 4.2 ± 1.6 mm. Menton (Me) moved significantly closer to the midsagittal plane, and the bilateral alare (Al) and alar curvature (Ac) moved laterally. In addition, pronasale (Prn), bilateral Al, Ac, subnasale (Sn), subspinale (Ss), labiale superior (Ls), sublabiale (Sl), pogonion (Pog), and Me moved upwards. The bilateral cheek bone (Cbp), Al, Ac, Prn, Sn, Ss, Ls, and stomion (Sto) moved forward. Li, Sl, Pog, and Me moved backward. Interestingly, poor correlation was found between soft tissue landmarks and hard tissue movements.

CONCLUSION

We observed 3D coordinate changes in several soft tissue landmarks in the middle and lower thirds of the face. The results of this study may be useful for estimating postoperative changes in similar patients.

Lip morphology estimation models based on three-dimensional images in a modern adult population from China

Lips are the main part of the lower facial soft tissue and are vital to forensic facial approximation (FFA). Facial soft tissue thickness (FSTT) and linear measurements in three dimensions are used in the quantitative analysis of lip morphology. With most FSTT analysis methods, the surface of soft tissue is unexplicit. Our study aimed to determine FSTT and explore the relationship between the hard and soft tissues of lips in different skeletal occlusions based on cone-beam CT (CBCT) and 3dMD images in a Chinese population. The FSTT of 11 landmarks in CBCT and 29 lip measurements in CBCT and 3dMD of 180 healthy Chinese individuals (90 males, 90 females) between 18 and 30 years were analyzed. The subjects were randomly divided into two groups with different skeletal occlusions distributed equally: 156 subjects in the experimental group to establish the prediction regression formulae of lip morphology and 24 subjects in the test group to assess the accuracy of the formulae. The results indicated that FSTT in the lower lip region varied among different skeletal occlusions. Furthermore, sex discrepancy was noted in the FSTT in midline landmarks and linear measurements. Measurements showing the highest correlation between soft and hard tissues were between total upper lip height and Ns-Pr (0.563 in males, 0.651 in females). The stepwise multiple regression equations were verified to be reliable with an average error of 1.246 mm. The method of combining CBCT with 3dMD provides a new perspective in predicting lip morphology and expands the database for FFA.

Evaluation of facial asymmetry by stereophotogrammetry in individuals with unilateral maxillary impacted canine

PURPOSE

The aim of this study is to compare the symmetry of the facial and dentoalveolar structures of patients with unilateral impacted maxillary canine teeth with a control group of individuals without impacted teeth using three-dimensional face scans.

METHODS

The study included 28 patients (10 females, 18 males) with unilateral impacted maxillary canine teeth and 28 patients (15 females, 13 males) without any impacted maxillary canine between 12 and 25 years of age. The 3dMDface™ (3dMD Inc., Atlanta, GA, USA) imaging system was used to obtain 3D face images. 3dMD Vultus® (3dMD Inc., Atlanta, GA, USA) software was used for the measurements.

RESULTS

According to the study findings, there were differences in linear measurements and volume measurements between the right and left sides of the face in patients with an impacted canine. However, these differences were not statistically significant. In patients with an impacted canine, surface differences between the right and left halves of the face were not found to be statistically different from the control group.

CONCLUSION

There was no difference in the amount of facial asymmetry between patients with unilateral maxillary impacted canine and patients with normal tooth alignment in the control group.

Automatic Assessment of 3-Dimensional Facial Soft Tissue Symmetry Before and After Orthognathic Surgery Using a Machine Learning Model: A Preliminary Experience

PURPOSE

An objective and quantitative assessment of facial symmetry is essential for the surgical planning and evaluation of treatment outcomes in orthognathic surgery (OGS). This study applied the transfer learning model with a convolutional neural network based on 3-dimensional (3D) contour line features to evaluate the facial symmetry before and after OGS.

METHODS

A total of 158 patients were recruited in a retrospective cohort study for the assessment and comparison of facial symmetry before and after OGS from January 2018 to March 2020. Three-dimensional facial photographs were captured by the 3dMD face system in a natural head position, with eyes looking forward, relaxed facial muscles, and habitual dental occlusion before and at least 6 months after surgery. Three-dimensional contour images were extracted from 3D facial images for the subsequent Web-based automatic assessment of facial symmetry by using the transfer learning with a convolutional neural network model.

RESULTS

The mean score of postoperative facial symmetry showed significant improvements from 2.74 to 3.52, and the improvement degree of facial symmetry (in percentage) after surgery was 21% using the constructed machine learning model. A Web-based system provided a user-friendly interface and quick assessment results for clinicians and was an effective doctor-patient communication tool.

CONCLUSIONS

This work was the first attempt to automatically assess the facial symmetry before and after surgery in an objective and quantitative value by using a machine learning model based on the 3D contour feature map.

Thresholds of Abnormality Perception in Facial Esthetics among Laypersons and Dental Professionals: Frontal Esthetics

Aim

To find thresholds at which laypersons and dental professionals perceive abnormalities in two facial frontal esthetics variables: facial symmetry and vertical harmony.

Materials and Methods

A baseline frontal image of a young male face with optimum facial proportions was generated from a real image using a photo editing software. Different facial asymmetry images were then generated from this image by manipulating the chin point position at 2 mm increment to the left side. Vertical harmony was perceived through manipulating lower anterior facial height (LAFH) at a ratio of 2% of increased and decreased heights. A total of 120 raters divided equally into four groups of laypersons, general dental practitioners (GDPs), orthodontists, and oral and maxillofacial surgeons (OMFSs) rated these images using an analog scale of 100 mm long. Using ANOVA and Tukey post hoc tests at P < 0.05, the image that showed the first statistical difference compared to the baseline was considered as a threshold of abnormality.

Results

The image of 4 mm asymmetry was defined by the laypersons and GDPs as the threshold of abnormality, while the orthodontists and OMFSs realized that at 2 mm. Laypersons and GDPs defined a threshold of 46% as an abnormal decrease in the LAFH and the other 2 groups at 48%. All dental professionals groups rated the image of 54% as an abnormal increase in the LAFH while laypersons perceived that at 56%.

Conclusion

These thresholds regarding frontal esthetics may contribute to the process of establishing proper orthodontic treatment planning that suits the highest facial esthetic standards.

Unilateral sagittal split osteotomy: effect on mandibular symmetry in the treatment of class III with laterognathia

The bilateral sagittal split osteotomy is considered the standard surgery to correct facial asymmetries. More recently, unilateral sagittal split osteotomy (USSO) was used to treat such malocclusions.

AIM

To assess facial symmetry following USSO in the treatment of class III laterognathia.

METHODS

Frontal facial photographs of four groups of patients were assessed: (1) pre-surgical group (n = 30) with skeletal asymmetry, (2) postsurgical group assessing patients of the first group 2 years after USSO, (3) control group (n = 30) of patients judged to have harmonious facial norms, and (4) mirrored group (n = 30) in which the control photographs were altered by duplicating the right half side of the face to replace the left half, thus creating perfectly symmetrical faces. All 120 photographs were distributed to 40 expert orthodontists to evaluate and score facial symmetry using the visual analog scale. Skin sensitivity and temporomandibular joint (TMJ) disorders were also assessed clinically pre and postsurgically.

RESULTS

Statistically significant differences were observed between the pre-surgical group and each of the postsurgical and control groups (p < 0.001). The control and postsurgical groups received similar scores of symmetry (p = 0.774). The mirrored group received statistically significantly higher symmetry scores than either of the control or the postsurgical groups (p < 0.001). A reduction in TMJ disorders was noted after USSO and all patients reported normal skin sensation 2 years post-surgery.

CONCLUSION

When indicated, USSO is a dependable and practical surgical approach to correct facial asymmetries associated with class III malocclusion.

Assessing the Influence of Chin Asymmetry on Perceived Facial Esthetics With 3-Dimensional Images

PURPOSE

We used 3-dimensinonal (3D) images to assess the influence of chin asymmetry on perceived facial esthetics, investigate the cognitive boundaries of chin asymmetry among orthodontists, general dentists, and laypersons, and provide quantitative reference for clinical treatment.

MATERIALS AND METHODS

A 3D facial image was obtained using the 3dMD imaging system (3dMD, Atlanta, GA). The chin was altered in 2-mm increments from 0 to 12 mm and to the left and right using the software program. These images were rated by 66 orthodontists, 89 general dentists, and 66 laypersons as 1) chin symmetry; 2) slight chin asymmetry but acceptable; and 3) serious asymmetry and treatment needed. Multivariate mixed linear regression and multivariate mixed logistic regression analyses were used for statistical data analysis. Descriptive and bivariate statistics were calculated, and statistical significance was considered present at P = .05.

RESULTS

The observers progressively increased the grade ratings and the desire for surgery for greater asymmetries (P < .001). Orthodontists and general dentists could perceive a chin deviation of 4 mm to the right and 2 mm to the left, with 8-mm deviation considered to require treatment. Laypersons had a clear perception of a 4-mm chin deviation, with 8 mm to the right and 10 mm to the left considered to require treatment. The right chin deflection was more easily perceived than was the left (P < .05).

CONCLUSIONS

Chin asymmetry has a great influence on facial esthetics. We found a statistically significant difference between clinicians (orthodontists and general dentists) and laypersons in the cognition of chin asymmetry and the recommendations for treatment.

Effect of facial profile convexity on the perception of mandibular asymmetry using three-dimensional stereophotogrammetric images

OBJECTIVE

The aim of this study was to test the hypothesis that sagittal anomalies have an effect on the perception of mandibular asymmetry. Secondly, it aimed to determine the asymmetry perception threshold of orthodontist and laypeople.

SETTING AND SAMPLE POPULATION

A total of 90 individuals were included in the study from different professions (Orthodontist: n:45, layperson: n:45).

MATERIALS & METHODS

The reference image was obtained with 3dMD device and selected from among the individuals with class I soft tissue relationship. In the sagittal direction, the chin area has been moved as to produce 5 and 10 degrees of change in facial convexity angle. Similarly, 0, 2, 4, 6, 8 and 10 mm changes were made and recorded in video format. Manipulated images were scored by participants with VAS method.

RESULTS

When differences between the groups were evaluated, the reference image was scored similarly by orthodontists and layperson (P: .017). No statistically significant difference was observed between the groups in other parameters (P > .05). Asymmetry in 0-2 mm range was evaluated by orthodontist and layperson and statistically insignificant (P > .05). Similarly, the change between 8 mm and 10 mm was different in both groups and statistically insignificant (P > .05). Also, when there was no asymmetry, the sagittal direction was differently scored by the participants in both groups and statistically insignificant (P > .05).

CONCLUSIONS

It was observed that the effect of sagittal direction changes on asymmetry perception was not statistically significant.

The maxillary incisor labial face tangent: clinical evaluation of maxillary incisor inclination in profile smiling view and idealized aesthetics

Background

To test the hypothesis that in profile smiling view, for ideal aesthetics, a tangent to the labial face of the maxillary central incisor crowns should be approximately parallel to the true vertical line and thereby perpendicular to the true horizontal line.

Methods

An idealized female image was created with computer software and manipulated using the same software to construct an “ideal” female profile image with proportions, and linear and angular soft tissue measurements, based on currently accepted criteria for idealized Caucasian profiles. The maxillary incisor labial face tangent was altered in 5° increments from 70 to 120°, creating a range of images, shown in random order to 70 observers (56 lay people and 14 clinicians), who ranked the images from the most to the least attractive. The main outcome was the preference ranks of image attractiveness given by the observers.

Results

The most attractive inclination of a tangent to the labial face of the maxillary incisor crowns in profile view in relation to the true horizontal line was 85°, i.e. 5° retroclined from a perpendicular 90° inclination. The most attractive range appears to be between 80 and 90°. Excessive proclination appeared to be less desirable than retroclination. Beyond 105° most observers recommend treatment.

Conclusion

In natural head position, the ideal inclination of the maxillary incisor crown labial face tangent in profile view will be approximately parallel to the true vertical line and thereby approximately perpendicular to the true horizontal line.

[Orthognathic surgery of mandibular asymmetry: which results can we expect with and without chin wing? A cohort out of 51 cases]

INTRODUCTION

The aim of this retrospective cohort is to evaluate the amount of postsurgical correction of soft and hard tissues in patients with mandibular asymmetries and to compare the results with and without surgery of the lower mandibular contour (chin wing…).

MATERIAL AND METHOD

Mandibular asymmetries cases of three surgeons were systematically included. The angles of deviation of the chin, bi-commissural, bi-gonic and occlusal were measured on face photography and radiography. A pre and post-surgical comparison was performed and the amount of correction was analyzed via the Wilcoxon statistical test.

RESULTS

51 patients (44 women and 7 men) were included. After surgery, the correction is significant for all measurements with an improvement of 44 to 60% depending on the measured angles. No patient is normalized but the small initial mandibular asymmetries are the closest to normal after surgery. The correction of the bi-commissural angle is controlled without being optimal (60% correction). The difficulty remains the horizontalization of the bi-gonial plan which is only corrected at 45%. Patients with mandibular margin surgery (chin wing…) showed the greatest improvement in bi-gonial (p = 0.0142) and occlusal (p = 0.0154) angles.

CONCLUSION

If surgery allows a significant correction of facial dissymmetry, this is not complete. Surgical procedures on the lower edge of the mandible such as the chin wing could provide a better correction especially for bi-gonial and occlusal angles.

A Comparative Review of Mandibular Orthognathic Surgeries with a Focus on Intraoral Vertico-sagittal Ramus Osteotomy

Severe dentofacial deformities require both orthodontics and surgical management to repair. Modern mandibular orthognathic surgery commonly uses sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO) methods to treat patients. However, complications like neurosensory disturbances and temporomandibular joint disorders are common following both procedures. In 1992, Choung introduced the intraoral vertico-sagittal ramus osteotomy (IVSRO) which led to a decrease in postoperative complications. The 'straight' IVSRO or Choung’s type II osteotomy has a 'condylotomy' effect that reduces iatrogenic temporomandibular joint symptoms and treats preoperative temporomandibular joint symptoms. This osteotomy type is especially applicable for prognathism with excessive flaring of the ramus and with temporomandibular joint dysfunction. The 'L-shaped' IVSRO or Choung’s type I osteotomy is indicated for patients with condylar hyperplasia and high condylar process fractures.

Clinician, dental student, and orthognathic patient perception of black-and-white silhouette lateral profile dimensions of ideal chin position in a Chinese population

OBJECTIVES

This study aimed to investigate differences in the influence of chin prominence and length on perception of facial aesthetics by Chinese dental clinicians, orthognathic patients, and dental students.

STUDY DESIGN

Male and female silhouette lateral profiles were modified to obtain 28 facial profiles by altering chin prominence and length by 3 mm in the sagittal and vertical planes. Images were rated by 70 clinicians, 30 orthognathic patients, and 100 dental students on a 7-point Likert scale.

RESULTS

Perceived attractiveness was highest when the male chin prominence (MCP) was -3 mm to 3 mm and the female chin prominence (FCP) was 3 mm. In contrast, male chin length (MCL) of 0 to 3 mm and female chin length (FCL) of 0 mm were considered the most attractive. In the sagittal and vertical profiles, MCP (-9 mm), FCP (-9 mm), FCL (-9 mm), and MCL (-9 mm) were ranked least attractive.

CONCLUSIONS

The overall aesthetic opinions of orthognathic patients, clinicians, and dental students are similar. The greater the retrusion or protrusion of the chin and the shorter or longer the chin length, the lower were the rates of facial aesthetics and the greater were the desire for surgery.

Effects of Objective 3-Dimensional Measures of Facial Shape and Symmetry on Perceptions of Facial Attractiveness

PURPOSE

Meeting patient desires for enhanced facial esthetics requires that providers have standardized and objective methods to measure esthetics. The authors evaluated the effects of objective 3-dimensional (3D) facial shape and asymmetry measurements derived from 3D facial images on perceptions of facial attractiveness.

MATERIALS AND METHODS

The 3D facial images of 313 adults in Iowa were digitized with 32 landmarks, and objective 3D facial measurements capturing symmetric and asymmetric components of shape variation, centroid size, and fluctuating asymmetry were obtained from the 3D coordinate data using geo-morphometric analyses. Frontal and profile images of study participants were rated for facial attractiveness by 10 volunteers (5 women and 5 men) on a 5-point Likert scale and a visual analog scale. Multivariate regression was used to identify the effects of the objective 3D facial measurements on attractiveness ratings.

RESULTS

Several objective 3D facial measurements had marked effects on attractiveness ratings. Shorter facial heights with protrusive chins, midface retrusion, faces with protrusive noses and thin lips, flat mandibular planes with deep labiomental folds, any cants of the lip commissures and floor of the nose, larger faces overall, and increased fluctuating asymmetry were rated as significantly (P < .001) less attractive.

CONCLUSION

Perceptions of facial attractiveness can be explained by specific 3D measurements of facial shapes and fluctuating asymmetry, which have important implications for clinical practice and research.

Discriminative Thresholds in Facial Asymmetry: A Review of the Literature

Background

Facial symmetry is intimately correlated with attractiveness. Perfect facial symmetry is disconcerting and a degree of facial asymmetry is considered normal. There is a lack of data on the limits of normality across facial subunits.

Objectives

This systematic review aims to establish categories of facial asymmetry perception for facial aesthetic units by establishing a discriminative threshold of "deformity perception" across facial subunits and a threshold for intervention (unacceptable asymmetry).

Methods

A review of the literature was performed across Medline and Embase databases using OvidSP. All prospective studies evaluating the perception of progressive facial asymmetry in laymen or clinicians using a two- or three-dimensional model were included. Studies that did not evaluate rates of perception at varying degrees of asymmetry were excluded as these did not allow for the identification of a perceptive threshold.

Results

Each facial feature possesses a unique threshold of perception defined by an abrupt, statistically significant increase in detection. Asymmetry of the eyelid position at rest is the most sensitive facial feature (perceptive threshold, 2 mm) (P < 0.02). This is followed by deviations of the oral commissure (3 mm) (P < 0.001), brow position (3.5 mm) (P < 0.001), nasal tip deviation (4 mm) (P < 0.001), and chin deviation (6 mm) (P < 0.001). Desire for surgery for worsening deformities beyond the intervention threshold is characterized by an exponential, rather than linear, correlation.

Conclusions

Categories of facial asymmetry perception establish a framework to counsel patients with facial asymmetries, and are a valuable adjunct to clinical judgment in the management of static and dynamic facial deformities.

Condylar hyperplasia: An updated review of the literature

Condylar hyperplasia (CH) is a rare disorder characterized by excessive bone growth that almost always presents unilaterally, resulting in facial asymmetry. Classification of the different types of CH can differ depending on the authors. Correct diagnosis is critical in determining the proper treatments and timing. This paper is a review of the recent literature on the epidemiology, etiology, diagnosis, classification, and surgical treatments of CH.

How does variation in lower anterior face height influence perceived attractiveness? A quantitative investigation

OBJECTIVE

The purpose of this investigation was to undertake an objective and quantitative evaluation of how severity of lower anterior face height (LAFH) variations influences perceived attractiveness.

DESIGN

Cross-sectional study

SETTING

St George's Hospital, London, UK PARTICIPANTS AND METHODS: The LAFH of an idealized male and female frontal facial image were altered in 2·5 mm increments from -20 to 20 mm (male images) and from -10 to 20 mm (female images), in order to represent reduction and increase in height of this region. These images were rated by a pre-selected group of pre-treatment orthognathic patients (n = 75), clinicians (n = 35) and laypersons (n = 75).

OUTCOME MEASURES

Ratings on a seven-point Likert scale.

RESULTS

With an increase in LAFH, desire for surgery became significant at 15-16 mm for male faces and 13-14 mm for female faces. With a reduction in LAFH, desire for surgery became significant at -14 to -17 mm for male faces; a smaller reduction of -6 to -8 mm led to a significant desire for surgery for female faces.

CONCLUSIONS

The classical vertical facial trisection canon of upper face height as one-third (33·3%), midface height as one-third (33·3%) and LAFH as one-third (33·3%) of total anterior face height may be used as an 'ideal' proportional ratio. Mild LAFH variations were largely acceptable. In terms of the percentage LAFH to total anterior face height (TAFH) and anterior face height (AFH), observers did not desire surgery for LAFH variations of 25-42% of TAFH (40-66% of AFH) for male faces, and 28-42% of TAFH (45-66% of AFH) for female faces.

Perception of oral and maxillofacial surgeons, orthodontists and laypersons in relation to the harmony of the smile

OBJECTIVE

Harmony is one of the main objectives in surgical and orthodontic treatment and this harmony must be present in the smile, as well as in the face. The aim of the present study was to assess the perceptions of professionals and laypersons in relation to the harmony of the smile of patients with or without vertical maxillary alterations.

MATERIALS AND METHODS

Sixty observers (oral and maxillofacial surgeons, orthodontists and laypersons) reported the degree of harmony of six smiles using an objective questionnaire and the participants indicated if there was a need for corrective surgery or not. The classification of observers was recorded on a Likert scale from 1 to 5. Mixed regression was used to determine differences between the three groups.

RESULTS

Statistically significant differences were found only for the harmony of the smile between the oral and maxillofacial surgeons and laypersons, with laypersons being more critical when assessing the smile. There was no statistical difference between the other groups for the harmony of the smile or the indication of corrective surgery. The patterns of greater or lesser harmony determined by observers during the smile were similar to those found in the literature as the ideal standard in relation to vertical maxillary positioning.

CONCLUSIONS

Laypersons had a tendency to be more critical in relation to facial harmony than surgeons, although no statistical differences were found in the other groups in relation to the harmony of the smile or indication for the corrective surgery. In addition, the patterns of greater or lesser harmony of the smile determined by the participants were similar to those found in the literature as the ideal standard in relation to vertical maxillary positioning. Overall, the present study demonstrates that adequate interaction between surgeons, orthodontists and laypersons is essential in order to achieve facial harmony with orthodontic and/or surgical treatment.

CLINICAL RELEVANCE

Opinion of specialists and laypersons about the smile in relation to the vertical positioning of the maxilla.

The perception of facial asymmetry using 3-dimensional simulated images

OBJECTIVE

To investigate the perception of facial asymmetry in young adults to identify the amounts of chin asymmetry that can be regarded as normal and may benefit from correction.

MATERIALS AND METHODS

Three-dimensional (3D) images of 56 individuals of mixed ethnicity were obtained and used to produce average 3D images of male and female faces. Distortion was then applied to these average faces using a 3D graphics package to simulate different amounts of chin point asymmetry. Five observer groups (lay individuals, dental students, dental care professionals, dental practitioners, and orthodontists) assessed timed presentations of 3D images, rating them as "normal," "acceptable," or "would benefit from correction." Time-to-event analysis was used to assess the level of chin asymmetry perceived as normal and beneficial for correction for each group.

RESULTS

The factors influencing the perception of facial asymmetry were the degree of asymmetry and the observer group. Direction of the asymmetry and gender of the assessed individual did not affect the perception of asymmetry, except in the 4- to 6-mm distortion range. The gender of the observer had no influence on perception. There were statistically significant differences in the amounts of asymmetry that the laypeople and orthodontists considered to be normal (5.6 ± 2.7 mm and 3.6 ± 1.5 mm, respectively; P < .001) and felt would benefit from surgical correction (11.8 ± 4.0 mm and 9.7 ± 3.0 mm, respectively; P  =  .001).

CONCLUSIONS

Perception of asymmetry is affected by the amount of asymmetry and the observer group, with orthodontists being more critical.

Face symmetry assessment abilities: Clinical implications for diagnosing asymmetry

INTRODUCTION

An accurate assessment of face symmetry is necessary for the development of a dentofacial diagnosis in orthodontics, and an understanding of individual differences in perception of face symmetry between patients and providers is needed to facilitate successful treatment.

METHODS

Orthodontists, general dentists, and control participants completed a series of tasks to assess symmetry. Judgments were made on pairs of upright faces (similar to the longitudinal assessment of photographic patient records), inverted faces, and dot patterns. Participants completed questionnaires regarding clinical practice, education level, and self-confidence ratings for symmetry assessment abilities.

RESULTS

Orthodontists showed expertise compared with controls (P <0.001), whereas dentists showed no advantage over controls. Orthodontists performed better than dentists, however, in only the most difficult face symmetry judgments (P = 0.006). For both orthodontists and dentists, accuracy increased significantly when assessing symmetry in upright vs inverted faces (t = 3.7, P = 0.001; t = 2.7, P = 0.02, respectively).

CONCLUSIONS

Orthodontists showed expertise in assessing face symmetry compared with both laypersons and general dentists, and they were more accurate when judging upright than inverted faces. When using accurate longitudinal photographic records to assess changing face symmetry, orthodontists are likely to be incorrect in less than 15% of cases, suggesting that assistance from some additional technology is infrequently needed for diagnosis.

Enhanced Facial Symmetry Assessment in Orthodontists

Assessing facial symmetry is an evolutionarily important process, which suggests that individual differences in this ability should exist. As existing data are inconclusive, the current study explored whether a group trained in facial symmetry assessment, orthodontists, possessed enhanced abilities. Symmetry assessment was measured using face and non-face stimuli among orthodontic residents and two control groups: university participants with no symmetry training and airport security luggage screeners, a group previously shown to possess expert visual search skills unrelated to facial symmetry. Orthodontic residents were more accurate at assessing symmetry in both upright and inverted faces compared to both control groups, but not for non-face stimuli. These differences are not likely due to motivational biases or a speed-accuracy tradeoff-orthodontic residents were slower than the university participants but not the security screeners. Understanding such individual differences in facial symmetry assessment may inform the perception of facial attractiveness.