Three-dimensional stereophotogrammetric analysis of 50 smiles: A study of dento-facial proportions

A smartphone application for personalized facial aesthetic monitoring

BACKGROUND

Methods available at home for capturing facial images to track changes in skin quality and evaluate skincare treatments are limited. In this study, we developed a smartphone camera application (app) for personalized facial aesthetic monitoring.

MATERIALS AND METHODS

A face alignment indicators (FAIN) system utilizing facial landmark detection, an artificial intelligence technique, to estimate key facial parts, was implemented into the app to maintain a consistent facial appearance during image capture. The FAIN system is composed of a fixed target indicator and an alignment indicator that dynamically changes its shape according to the user's face position, size, and orientation. Users align their faces to match the alignment indicator with the fixed target indicator, and the image is automatically captured when alignment is achieved.

RESULTS

We investigated the app's effectiveness in ensuring a consistent facial appearance by analyzing both geometric and colorimetric data. Geometric information from captured faces and colorimetric data from stickers applied to the faces were utilized. The coefficients of variation (CVs) for the L*, a*, and b* values of the stickers were higher compared to those measured by a colorimeter, with CVs of 14.9 times, 8.14 times, and 4.41 times for L*, a*, and b*, respectively. To assess the feasibility of the app for facial aesthetic monitoring, we tracked changes in pseudo-skin color on the cheek of a participant using skin-colored stickers. As a result, we observed the smallest color difference ∆Eab of 1.901, which can be considered as the experimentally validated detection limit using images acquired by the app.

CONCLUSION

While the current monitoring method is a relative quantification approach, it contributes to evidence-based evaluations of skincare treatments.

Three-dimensional analysis of posed smile in adults: A scoping review

This scoping review investigated the evidence on the three-dimensional analysis of a posed smile in adults to discover any research gaps in this research area. Electronic searches of articles written in English were performed using the four databases of Embase, PubMed, Springer, and Web of Science with publications from 2010 to 2023. Reference lists were also manually searched to identify additional studies. The results showed that 13 cross-sectional descriptive studies from Asia, Europe, North and South America met our inclusion criteria. Studies mainly focused on linear and angle measurement for resting and smiling faces and landmark movement from resting to smiling. Most studies conducted analysis of smiles stratified by sex, ethnicity, smile type, dental occlusion, skeletal pattern, and age. Two studies compared smiling with the resting position and one study compared the attractive smiling group with the ordinary group. Our scoping review revealed the insufficiency of some measurement methods, such as those employing area, volume, and soft tissue thickness. Furthermore, few studies were conducted in Asian populations, and comparisons of various smile types, overjet types, horizontal skeletal patterns, and comparisons of smiles between people with untreated normal occlusion and those who had been orthodontically treated were lacking.

Perceptual difference of smile aesthetics between 2-dimensional photographs and 3-dimensional dentofacial images: a cross-sectional study

BACKGROUND

The aim of this study was to compare the perceptual difference of smile aesthetics between 2D photographs and 3D dentofacial images as perceived by orthodontists and graduate students.

METHODS

Forty-eight subjects finished orthodontic treatment were recruited with 2D photographs of frontal, oblique and lateral views as well as 3D dentofacial images. Twelve senior orthodontists and 13 postgraduate students were asked to rate the 2D and 3D smile simulations based on visual analog scale (VAS) and to vote for smile features that affect the attractiveness of smile. At the end, they completed a questionnaire about their views on different smile simulations. Wilcoxon signed-rank, Bland-Altman analysis, and multiple linear regression were used to compare the ratings and votes of smile perception between raters and between records.

RESULTS

Orthodontists and postgraduate students rated smile consistently with 2D photographs, while orthodontists tended to give a higher rate for unattractive smiles and a lower rate for attractive smiles with 3D dentofacial images. The 3D dentofacial images were rated significantly lower than 2D photographs and the voting of most of the smile features showed significant negative main effect on VAS scores, while the effect of demographic characteristics of raters, voting on visible width of upper dentition and buccal corridor was not significant. In addition, a significant negative main effect of commissure and facial profile was found on the rating discrepancy between 2D and 3D images.

CONCLUSIONS

Senior orthodontists tend to perceived 3D images more conservatively in smile evaluation. 3D dentofacial images were rated lower than 2D photographs and most of the smile features affect the aesthetic perception of smile. The perceptual difference of commissure and facial profile contributed to the lower ratings in 3D dentofacial images.

Evaluation of Dental Golden Ratio in Terms of Facial Esthetics

Aim and Objectives:

This cross-sectional study examined the Bolton index of 6 maxillary anterior teeth and the facial esthetic ratios in the Turkish population with healthy facial appearance.

Materials and Methods:

Face photographs of the subjects, taken using a DSLR camera, were fixed in the Frankfort horizontal plane. The measurements were made on the images using ImageJ 1.52a software and certain ratios of face and teeth were calculated such as Bolton index (BI). Differences between genders were evaluated and comparisons with golden ratio of 1.618 were conducted on SPSS.

Results:

Males had significantly higher upper, middle, lower, and total facial height compared to females ( P < .001, P = 0.0257, P = .0243, P < .001, respectively). Right to left distance of labial commissure (LC)/distance from the distal edge of right canine to the distal edge of left canine ratio had golden proportion. Ratio of naso-menton length to facial width showed golden ratio only in males. The ratio of the width of upper middle incisor to the width of canine tooth also showed golden ratio in both genders.

Conclusions:

The present study presents noteworthy data about facial and teeth ratios of the young adult Turkish population that will guide plastic surgeons and orthodontists in clinical practice.