BACKGROUND: The protective effectiveness of an N95 respirator depends on the filtration efficiency of the material from which the N95 respirator is made of, as well as the wearers' facial fit. The facial fit of an N95 respirator mainly depends on the degree of matching between the wearers' facial dimension characteristics and the N95 respirator. Quantitative fit testing objectively evaluates the fit of N95 respirators; however, it is not easy to promote because of the limitations of testing conditions. The aim of this study is to establish a fit prediction model of N95 respirator based on facial images. METHODS: Facial images and fit factor (FF) value of 5 N95 respirators were gathered from 299 medical staffs in 10 hospitals in Beijing. Face geometry measurement was based on 3D face modelling, and the American TSI-8038 Porta Count Pro+ was used to conduct quantitative fit test. Multiple linear regression analysis was employed to identify facial dimensional features that significantly influenced the fit of N95 respirators. Through matching training of facial image and FF values, a fit prediction model has been established, enabling rapid recommendation of N95 respirators meeting the fit standard via facial image recognition. RESULTS: A fit prediction model for N95 respirators based on facial images has been developed, which enables the rapid recommendation of N95 respirators with acceptable FF value for healthcare personnel. The model demonstrated an accuracy of 55.93%, a precision of 98.43%, a recall of 51.65%, and an F1 score of 0.68. CONCLUSIONS It is feasible to utilize computer-based facial recognition technology to rapidly recommend N95 respirators for medical personnel. Given the high level of accuracy achieved, the model demonstrates significant potential for practical application.
Humans ; Face/anatomy & histology* ; N95 Respirators/standards* ; Male ; Adult ; Female ; Middle Aged ; Beijing

OBJECTIVE: To establish a similarity measurement model for patients with dentofacial deformity based on 3D craniofacial features and to validate the similarity results with quantifying subjective expert scoring. METHODS: In the study, 52 cases of patients with skeletal Class Ⅲ malocclusions who underwent bimaxillary surgery and preoperative orthodontic treatment at Peking University School and Hospital of Stomatology from January 2020 to December 2022, including 26 males and 26 females, were selected and divided into 2 groups by sex. One patient in each group was randomly selected as a reference sample, and the others were set as test samples. Three senior surgeons rated the similarity scores between the test samples and the reference sample. Similarity scores ranged from 1 to 10, where 1 was completely different, and 10 was exactly the same. Scores larger than 7.5 was considered as clinically similar. Preoperative cone beam computed tomography (CBCT) and 3D facial images of the patients were collected. The three-dimensional hard and soft tissue features, including distances, angles and 3D point cloud features were extracted. The similarity measurement model was then established to fit with the experts' similarity scoring by feature selection algorithm and linear regression model. To verify the reliability of the model, 14 new patients were selected and input to similarity measurement model for finding similar cases. The similarity scoring of these similar cases were rated by experts, and used to evaluate the reliability of the model. RESULTS: The similarity metric models indicated that the features of the middle and lower craniofacial features were the main features to influence the craniofacial similarity. The main features that were related to the expert' s similarity scoring included distance of anterior nasal spine-menton (ANS-Me), distance of right upper canion point-Frankfurt horizontal plane (U3RH), distance of left superior point of the condyle-left gonion (CoL-GoL), distance of left gonion-menton (CoL-Me), distance of pogonion-midsagittal plane (Pog-MSP), distance of right alar base-left alar base (AlR-AlL), angle of pronasale-soft tissue pogonion-labrale inferius (Pn-Pog' -Li), distance of trichion-right tragus (Tri-TraR), distance of left exocanthion-left alar base (ExL-AlL), lower 1/3 of skeletal face, middle and lower 2/3 of skeletal face and upper lip region of soft tissue. Fourteen new patients were chosen to evaluate the model. The similar cases selected by the model had an average experts' similarity scoring of 7.627± 0.711, which was not significantly different with 7.5. CONCLUSION The similarity measurement model established by this model could find the similar cases which highly matched experts' subjective similarity scoring. The study could be further used for similar cases retrieval in skeletal Ⅲ malocclusion patients.
Humans ; Male ; Female ; Imaging, Three-Dimensional/methods* ; Cone-Beam Computed Tomography ; Malocclusion, Angle Class III/surgery* ; Orthognathic Surgical Procedures/methods* ; Face/anatomy & histology* ; Cephalometry/methods* ; Adult ; Adolescent ; Dentofacial Deformities/surgery* ; Young Adult

OBJECTIVE: To compare the registration accuracy of cone beam computed tomography (CBCT) images while registering to virtual craniodentofacial patients based on soft tissue and the dentition registration method. METHODS: Virtual dentofacial patients out of 13 selected participants who needed CBCT scanning were established by impression with a registered-block impression (RBI) based on digital dental images, three-dimensional (3D) facial images and maxillofacial CBCT images. CBCT images were processed in the Mimics software program, establishing the craniofacial virtual patients based on CBCT images (CCTs). Registration between virtual patients from RBI and CCT, using the soft tissue in lower half face (STE) and dentition (DTN) as the reference area, respectively, forming two kinds of virtual craniofacial patients based on digital dental images, 3D facial images and skeletal images of CBCT (hiding the soft tissue and dental casts from CBCT). Three-dimensional deviation analysis was performed in the upper half face and lower half face of facial images from CBCT between two kinds of virtual craniodentofacial patients and compared with 3D facial images from RBI and recorded as root mean square error (RMSE). Paired-t test was used to compare the deviations of RMSEs between the upper and lower half of the face and the upper half of the face of facial images from CCT, respectively, between the two kinds of virtual craniodentofacial patients based on STE and DTN methods. RESULTS: Paired-t tests showed that there was no statistically significant difference between the upper and lower half faces of facial images from CCT between STE and DTN (P>0.05), but the deviation of RMSEs of the upper half face of facial images from CCT in STE was smaller than those in DTN [(1.696±0.420) mm vs. (1.752±0.424) mm, P < 0.01]. CONCLUSION The registration accuracy of CBCT registered in virtual craniodentofacial patients using soft tissue as the reference area was higher.
Humans ; Cone-Beam Computed Tomography/methods* ; Imaging, Three-Dimensional/methods* ; Male ; Face/anatomy & histology* ; Female ; Adult ; Image Processing, Computer-Assisted/methods* ; Young Adult ; User-Computer Interface

OBJECTIVE: To investigate the changes and symmetry of facial soft tissue during posed smile, to analyze the feature of posed smile in different gender, and verify the reproducibility of posed smile. METHODS: Three-dimensional (3D) facial images of 41 adults (16 males and 25 females with an average age of 26.76±2.70 years) which were taken by FaceScan three-dimensional sensor, including one rest position and two posed smile images. Then these images were imported into 3D soft tissue analysis software for model repositioning. 3D morphable model method (3DMM) was carried out to automatic landmarks setting. After that, the measurement of the eyes, cheeks, nose and perioral area were carried out for 3D soft tissue analysis. Finally, the changes and symmetry of the soft tissues between the two expression states and the gender differences during the posed smiles were compared. Meanwhile, the reproducibility of posed smile was statistically tested. RESULTS: Compared with the rest position, except for nasolabial angle (1.45°±7.65°), the measurements of 3D soft tissue in other region were changed in posed smile (P < 0.001). It should be noted that the eye region was also significantly changed (P < 0.001). Furthermore, the prominent feature of posed smile was that the alar base length became longer, the upper and lower vermilions were narrow and thin, and the mentolabial furrows became shallow. Meanwhile the chin extended anteriorly while the mouth retracted; During posed smile, the labial fissure asymmetry [2.78 (1.73, 3.49) mm], mid-infraorbital asymmetry [2.36 (1.22, 3.27) mm] and outercanthal asymmetry [2.31(1.29, 2.80) mm] were most apparent. Compared with the rest position, the asymmetry was not significantly increased except for cheilion and alar curvature points during the posed smile (P>0.05). In the posed smile, the changes of the right palpebral fissure height and the thickness of lower vermilion (|Li-Stoi| _z) of males were greater than those of females (P < 0.05), and asymmetry of exocanthion and cheekbone increased more than that of females (P < 0.05). There was no obvious difference between the two posed smiles. CONCLUSION In this study, during the posed smile the soft tissues of the eyes, cheeks, nose, lips and chin changed in different degrees, and the asymmetry of cheilion and alar curvature point was greater than that of the rest position; In addition, the reproducibility of posed smile was excellent, which can be a reference for clinical aesthetics and functional research of smile.
Humans ; Smiling/physiology* ; Female ; Male ; Adult ; Imaging, Three-Dimensional/methods* ; Face/anatomy & histology* ; Young Adult ; Facial Expression

OBJECTIVES: This study aimed to analyze the correlations and proportional relationships between maxillary anterior teeth (MAT) and facial measurements in Han Chinese individuals with the most attractive smiles, as evaluated by dental professionals. METHODS: Ten dentists with more than 5 years of clinical experience from different professional directions in a tertiary stomatological hospital were selected to evaluate the smile attractiveness of volunteers by visual analogue scale (VAS). Eighty-eight Han volunteers with the most attractive smile were selected. The perceived width of the MAT, the dimensions (height and width) of the maxillary central incisors (MCI), and the facial dimensions (intercanthal distance, interzygomatic distance, interalar distance, facial height and lower facial height) of the volunteers were measured on the frontal photos of the smile, digital oral model, and 3D face model. Pearson correlation analysis was performed to analyze linear correlations, and regression analysis was carried out to explore the proportional relationships. Reliability analysis using the intraclass correlation coefficient verified the stability of these proportional relationships. In addition, the correlations between MAT perceived width and the proportional relationships of (MCI) height to width ratio, with facial dimensions were explored and their reliability was verified. RESULTS: In Han Chinese individuals with the most attractive smiles, as evaluated by dental professionals, the Pearson correlation coefficients among MAT perceived widths were 0.813, 0.389, and 0.560. A proportional relationship existed between the lateral incisor and central incisor, and the ratio was 0.729. No significant correlations were found between MCI and the inner canthal distance, zygomatic distance, interalar distance, facial height, or the lower one-third facial height except for a negative correlation (r=-0.357) between MCI height and facial height in males and a positive correlation (r=0.249) between MCI width and interalar width when genders were combined. CONCLUSIONS Correlations exist among MAT perceived widths in Han Chinese individuals with the most attractive smiles, as evaluated by dental professionals. Partial correlations are observed between MCI height and width and facial measurements. The perceived width of the lateral incisor can serve as a reference indicator for predicting the perceived width of the central incisor, providing a reference for the aesthetic restoration of MAT in the Han ethnicity population.
Adult ; Female ; Humans ; Male ; China ; Esthetics, Dental ; Face/anatomy & histology* ; Incisor/anatomy & histology* ; Maxilla/anatomy & histology* ; Smiling ; East Asian People

Objective: To explore the establishment of an efficient and automatic method to determine anatomical landmarks in three-dimensional (3D) facial data, and to evaluate the effectiveness of this method in determining landmarks. Methods: A total of 30 male patients with tooth defect or dentition defect (with good facial symmetry) who visited the Department of Prosthodontics, Peking University School and Hospital of Stomatology from June to August 2021 were selected, and these participants' age was between 18-45 years. 3D facial data of patients was collected and the size normalization and overlap alignment were performed based on the Procrustes analysis algorithm. A 3D face average model was built in Geomagic Studio 2013 software, and a 3D face template was built through parametric processing. MeshLab 2020 software was used to determine the serial number information of 32 facial anatomical landmarks (10 midline landmarks and 22 bilateral landmarks). Five male patients with no mandibular deviation and 5 with mild mandibular deviation were selected from the Department of Orthodontics or Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology from June to August 2021. 3D facial data of patients was collected as test data. Based on the 3D face template and the serial number information of the facial anatomical landmarks, the coordinates of 32 facial anatomical landmarks on the test data were automatically determined with the help of the MeshMonk non-rigid registration algorithm program, as the data for the template method to determine the landmarks. The positions of 32 facial anatomical landmarks on the test data were manually determined by the same attending physician, and the coordinates of the landmarks were recorded as the data for determining landmarks by the expert method. Calculated the distance value of the coordinates of facial anatomical landmarks between the template method and the expert method, as the landmark localization error, and evaluated the effect of the template method in determining the landmarks. Results: For 5 patients with no mandibular deviation, the landmark localization error of all facial anatomical landmarks by template method was (1.65±1.19) mm, the landmark localization error of the midline facial anatomical landmarks was (1.19±0.45) mm, the landmark localization error of bilateral facial anatomical landmarks was (1.85±1.33) mm. For 5 patients with mild mandibular deviation, the landmark localization error of all facial anatomical landmarks by template method was (2.55±2.22) mm, the landmark localization error of the midline facial anatomical landmarks was (1.85±1.13) mm, the landmark localization error of bilateral facial anatomical landmarks was (2.87±2.45) mm. Conclusions: The automatic determination method of facial anatomical landmarks proposed in this study has certain feasibility, and the determination effect of midline facial anatomical landmarks is better than that of bilateral facial anatomical landmarks. The effect of determining facial anatomical landmarks in patients without mandibular deviation is better than that in patients with mild mandibular deviation.
Adolescent ; Adult ; Algorithms ; Anatomic Landmarks ; Cephalometry/methods* ; Face/anatomy & histology* ; Female ; Humans ; Imaging, Three-Dimensional/methods* ; Male ; Malocclusion ; Middle Aged ; Orthodontics ; Software ; Young Adult

Individual identification is one of the research hotspots in the practice of forensic science, and the judgment is usually built on the comparison of the unique biological characteristics of the individual, such as fingerprints, iris and DNA. With the dramatic increase in the number of cases related to video image investigations, there is an increasing need for the technology to identify individuals based on the macroscopic comparison of facial appearance biometrics. At present, with the introduction of computer three-dimensional (3D) modeling and 3D superimposition comparison technology, considerable progress has been made in individual identification methods based on macroscopic comparison of facial appearance biometrics. This paper reviews individual facial appearance biometric methods based on macroscopical comparison, comprehensively analyzes the advantages and limitations of different methods, and puts forward recommendations and prospects for subsequent research.
Biometric Identification ; Biometry/methods* ; Face/anatomy & histology* ; Forensic Sciences/methods* ; Humans

OBJECTIVES: To search age-correlated facial features and construct an age estimation model based on the three-dimensional （3D） facial images of Xinjiang Uygur males, and to structure individual face images of old age and young age. METHODS: Pretreatment was performed to collect 105 3D facial images of Xingjiang Uygur males aged between 17-57 years by Artec Studio software. The facial images were transferred to high-density 3D dot matrix data by FaceAnalysis software, and each image could be represented with 32 251 vertexes. Central correction of the facial images was done and all the data were aligned to a standard coordinate frame by generalized Procrustes analysis （GPA）. The age estimation model was established by partial least square regression （PLSR）. Furthermore, the changes of age-correlated facial features were presented on the heat map of average face, and the reconstruction of facial images at different ages was performed based on this model. RESULTS: With age, the average faces showed a series of changes including the nasolabial sulcus deepening, cheek sinking, cheekbone protruding and eye corner drooping. The Pearson correlation coefficient （r） between estimated age and chronological age was 0.71. The mean absolute deviation （MAD） of age estimation was 6.37 years. The results of age estimation in >30-40 years group showed a best accuracy （MAD=4.27 years）, and the deviations increased with age after 40 years. The composite facial images represented a significant result with age on facial morphological features and aging. CONCLUSIONS The results of this study reveal the age-correlated facial features and aging markers in Uygur population, which help to construct a reliable age estimation model.
Adolescent ; Adult ; Aging/physiology* ; Face/anatomy & histology* ; Head/anatomy & histology* ; Humans ; Imaging, Three-Dimensional/methods* ; Male ; Middle Aged ; Software ; Young Adult

OBJECTIVETo investigate the facial aging analysis of 1200 Han adult people in Dalian with iris diameter, so as to provide reference for facial rejuvenation in Han people.

METHODS1200 facial digital photographs from the second-generation ID card of China were stratified randomly selected as the research sample, excluding facial deformity, tattooing eyebrow, tattooing lid margin, ptosis, lip grain and eyebrow deformity cases, as well as the cases whose join point of upper eyelid and lower eyelid not exposed at the nasal side. These photos were divided into six cohorts: female aged 18, 38, and 68 years old; and male aged 18, 38, and 68 years old, with 200 cases in each cohort. The individual iris diameter was divided into 20 equal parts in each photograph, with each part marked one unit as individual iris diameter ruler. Ten values were made from a horizontal plane between the medial canthus to ten points at one face ( the line between two medial canthus is used as the horizontal line, circumocular and facial soft tissue were measured with individual iris diameter ruler on the photographs), then the results were analyzed with Adobe Photoshop software.

RESULTSThere are statistically significant differences in eyebrow height (36.42 ± 4.22 unit in 18 years old male group, 40.22 ± 6.90 unit in 38 years old male group, 34.83 ± 9.39 unit in 68 years old male group; 37.59 ± 6.72 unit in 18 years old female group, 41.09 ± 5.15 unit in 38 years old female group, 36.84 ± 9.45 unit in 68 years old female group), palpebral fissure height, physiognomic external canthus height, palpebral fissure width, pupil height and other items (P < 0.05).

CONCLUSIONS(1) The brow position rises to the peak level at middle age (38 years old group), then drops down gradually with aging. (2) The physiognomic external canthus moves towards the nasal side and caudal side with aging. (3) Eyeball moves towards caudal side with aging. (4) The soft tissue around bilateral angle of mouth, nasal tip and submaxilla moves towards caudal side with aging. (5) The measurement of individual iris diameter ruler can apply to analyze the aging changes of facial soft tissue, and is more suitable for the case when facial photographs are taken at different distances.

Adolescent ; Adult ; Age Factors ; Aged ; Aging ; China ; ethnology ; Cohort Studies ; Eye ; anatomy & histology ; Eyebrows ; anatomy & histology ; Face ; anatomy & histology ; Female ; Humans ; Iris ; anatomy & histology ; Lip ; anatomy & histology ; Male ; Nose ; anatomy & histology ; Photography ; Rejuvenation ; Sex Factors

OBJECTIVE: To establish regression model between craniofacial lines and body height by measuring craniofacial lines in Southwest Han males using CT and to accumulate data for the study of forensic anthropology. METHODS: Head CT data of 273 Han males in Southwest were collected and 7 craniofacial lines were determined. Multiplanar reconstruction and volume rendering were performed by image post-processing software and the selected lines were measured. The relationship between each measuring indicator and body height was analyzed using SPSS 21.0 software. The regression equation of body height estimation was established and 50 samples were selected again and put into the mathematics models to verify its accuracy. RESULTS: The linear regression equations of 7 lines were established (P < 0.05). The correlation coefficients of the unary linear regression equations were 0.190-0.439 and the standard errors of the estimate (SEE) were 4.597-5.023 cm. The correlation coefficients of the multiple linear regression equation were 0.494-0.524 and the SEE were 4.418-4.458 cm. The return tests showed that the highest ± 1SEE accuracy of the multiple regression equation: y = 83.959+3.589 x6+2.573 x2, were 30%; and the highest ± 2SEE accuracy of the multiple regression equation: y = 72.646+3.316 x6+1.586 x2+1.553 x4+2.211 x3, were 92%. CONCLUSION There is significant linear correlation between 7 selected lines and the stature in this study, and the plural linear regression equation established could be applied for estimating the stature of Southwest Han males.
Asian People ; Body Height ; Face/anatomy & histology* ; Forensic Anthropology ; Head/anatomy & histology* ; Humans ; Image Processing, Computer-Assisted ; Linear Models ; Male ; Software ; Tomography, X-Ray Computed