Three-dimensional Facial Scans Research Articles

Comparative Accuracy of Stationary and Smartphone-Based Photogrammetry in Oral and Maxillofacial Surgery: A Clinical Study.

Background: Three-dimensional facial scan technologies, such as stereophotogrammetry, are frequently used in oral and maxillofacial surgery, dentistry, and plastic surgery to assess patient outcomes and plan surgical procedures. Most facial scanners rely on stationary clinical systems, which provide high accuracy and reliability in generating 3D representations of the human face; however, they are cost-intensive and immobile. Recently, smartphone-based facial scan applications that use stereophotogrammetry have been developed. These applications are cost-effective and more accessible than existing stationary systems. Methods: In this study, we compared the accuracy of three different smartphone applications-EM3D, Polycam, and ScandyPro-on an iPhone 14 Pro, which utilizes Apple's LiDAR (Light Detection and Ranging) technology, to a stationary system by 3DMD, which is considered a gold standard in many studies. Results: The applications included in the study have demonstrated the capability to perform accurately in clinical settings, with mean surface distances of 1.46 mm for EM3D, 1.66 mm for Polycam, and 1.61 mm for ScandyPro. Conclusions: These results suggest that smartphone-based facial scan systems could be a viable alternative, particularly in resource-limited settings. However, further research and collaboration between academia and industry are necessary to fully integrate these technologies into clinical practice.

Influence of Head Circumference on the Accuracy of Facial Scanning: An In vitro Study

ObjectivesThis study aimed to investigate the impact of head circumference on the accuracy of three-dimensional (3D) facial scans, focusing on trueness and precision across three mannequin heads of different sizes. Material and methodsThree 3D-printed mannequin heads with circumferences of 30, 50, and 65 cm were used. Ten facial landmarks were identified to measure seven interlandmark distances and two angles. Direct anthropometric measurement, serving as the reference value, was taken using a digital vernier calliper for linear distance, and angle was calculated using the law of cosines. Each head was scanned six times using two systems: a dual-structured light facial scanner (iTom) and a stereophotogrammetry system (3dMD). Digital measurements were analysed using Meshlab and Blender for distances and angles, respectively. Trueness values were determined by comparing measurements to reference measurements, while precision values were derived from the variability among the six scans. Statistical analysis was performed using the Kruskal–Wallis test due to nonhomogeneous variances, followed by Bonferroni correction for pairwise group comparisons. ResultsFor each scanning system, overall deviations in trueness and precision significantly increased with head circumference. Five of the seven distances and one angle showed significant compromises in trueness with larger head circumferences. Most measurements exhibited significant precision decreasing due to head circumference changes, except for N-Pn and Pn-Sn. Additionally, 3dMD displayed higher overall trueness compared to iTom, with five out of seven linear measurements and one angular measurement showing better results. ConclusionHead circumference significantly affects both trueness and precision of 3D facial scans for both technologies, suggesting that facial imaging should be used with caution for larger faces. Selecting an appropriate scanning system, such as 3dMD, can help mitigate the negative effects of scanning larger objects.

Comparative analysis of 3D tomography based soft tissue rendering and Proface facial scanning systems in orthognathic surgery

PurposeThis study aimed to investigate the linear and angular differences in the nasolabial soft tissue in patients who underwent bimaxillary orthognathic surgery using two different three-dimensional imaging methods. Furthermore, the advantages, disadvantages, and limitations of these methods were determined after comparing the data obtained from the imaging methods used in the study. Materials and MethodsPreoperative (T0) and 6-months postoperative (T1) cone-beam computed tomography (CBCT) and three-dimensional facial scanning (3DFS) data from 22 patients who underwent maxillary advancement surgery were examined. The DICOM (Digital Imaging and Communications in Medicine) data (CBCT group) and “.obj” format images (3DFS group) of the patients were analyzed using Dolphin software (Dolphin Imaging®, Version 12, Chatsworth, CA, USA). The linear and angular soft tissue measurements were calculated after determining the reference anatomical landmarks for both groups. ResultsMeasurements with CBCT and 3DFS imaging methods were compared at T0, T1, and all measurements (T0+T1). No statistically significant difference was observed between the CBCT and 3DFS groups for five measurements performed at T0 and T0+T1, but statistically significant differences were observed between the groups for the other seven measurements. There was no statistically significant difference between the CBCT and 3DFS groups for six measurements at T1, but there were statistically significant differences between the groups for the other six measurements. After reviewing the postoperative differences in the nasolabial soft tissue, a statistically significant increase in four linear and one angular measurement in the 3DFS group was observed, and there was a statistically significant increase in two linear and two angular measurements in the CBCT group. Upon comparison of postoperative differences in soft tissue alterations, no statistically significant difference between the 3DFS group and the CBCT group were observed in any of the soft tissue measurements. ConclusionOrthognathic surgery has significant effects on nose width and upper lip morphology. Although both 3DFS and CBCT methods can be used to evaluate such effects, the results of the present study revealed differences in sensitivity and limitations between the two methods. Thus, surgical outcomes should be evaluated in consideration of the abovementioned parameters.

Network analysis of three-dimensional hard-soft tissue relationships in the lower 1/3 of the face: skeletal Class I-normodivergent malocclusion versus Class II-hyperdivergent malocclusion

BackgroundThe determining effect of facial hard tissues on soft tissue morphology in orthodontic patients has yet to be explained. The aim of this study was to clarify the hard-soft tissue relationships of the lower 1/3 of the face in skeletal Class II-hyperdivergent patients compared with those in Class I-normodivergent patients using network analysis.MethodsFifty-two adult patients (42 females, 10 males; age, 26.58 ± 5.80 years) were divided into two groups: Group 1, 25 subjects, skeletal Class I normodivergent pattern with straight profile; Group 2, 27 subjects, skeletal Class II hyperdivergent pattern with convex profile. Pretreatment cone-beam computed tomography and three-dimensional facial scans were taken and superimposed, on which landmarks were identified manually, and their coordinate values were used for network analysis.Results(1) In sagittal direction, Group 2 correlations were generally weaker than Group 1. In both the vertical and sagittal directions of Group 1, the most influential hard tissue landmarks to soft tissues were located between the level of cemento-enamel junction of upper teeth and root apex of lower teeth. In Group 2, the hard tissue landmarks with the greatest influence in vertical direction were distributed more forward and downward than in Group 1. (2) In Group 1, all the correlations for vertical-hard tissue to sagittal-soft tissue position and sagittal-hard tissue to vertical-soft tissue position were positive. However, Group 2 correlations between vertical-hard tissue and sagittal-soft tissue positions were mostly negative. Between sagittal-hard tissue and vertical-soft tissue positions, Group 2 correlations were negative for mandible, and were positive for maxilla and teeth.ConclusionCompared with Class I normodivergent patients with straight profile, Class II hyperdivergent patients with convex profile had more variations in soft tissue morphology in sagittal direction. In vertical direction, the most relevant hard tissue landmarks on which soft tissue predictions should be based were distributed more forward and downward in Class II hyperdivergent patients with convex profile. Class II hyperdivergent pattern with convex profile was an imbalanced phenotype concerning sagittal and vertical positions of maxillofacial hard and soft tissues.

Using three-dimensional geometric morphometry for facial analysis in patients with the oculo-auriculo-vertebral spectrum.

To utilize three-dimensional (3D) geometric morphometry for visualization of the level of facial asymmetry in patients with the oculo-auriculo-vertebral spectrum (OAVS). Three-dimensional facial scans of 25 Czech patients with OAVS were processed. The patients were divided into subgroups according to Pruzansky classification. For 13 of them, second 3D facial scans were obtained. The 3D facial scans were processed using geometric morphometry. Soft tissue facial asymmetry in the sagittal plane and its changes in two time spots were visualized using colour-coded maps with a thermometre-like scale. Individual facial asymmetry was visualized in all patients as well as the mean facial asymmetry for every Pruzansky subgroup. The mean colour-coded maps of type I and type IIA subgroups showed no differences in facial asymmetry, more pronounced asymmetry in the middle and the lower facial third was found between type IIA and type IIB (maximum 1.5 mm) and between type IIB and type III (maximum 2 mm). The degree of intensity facial asymmetry in affected middle and lower facial thirds did not change distinctly during the two time spots in all subgroups. The 3D geometric morphometry in OAVS patients could be a useful tool for objective facial asymmetry assessment in patients with OAVS. The calculated colour-coded maps are illustrative and useful for clinical evaluation.

Validity and Reliability of New Three-Dimensional Reference Systems for Soft Tissue Analysis Using Non-Ionizing Three-Dimensional Imaging

Background: The aim of this study was to evaluate the accuracy and the repeatability of two reference systems for three-dimensional facial scans (FSs) compared with a reference system based on cone-beam computed tomography (CBCT). Subjects and methods: A total of sixty subjects, thirty growing participants (8–17 years old) and thirty non-growing participants (older than 21 years old), with FSs and full-field-of-view CBCT were included. Two different reference systems on the same FS were constructed. To assess validity, the two reference systems based on FSs were compared with the reference systems built using the CBCT scans. After two weeks, all of the FSs were reassessed to evaluate intra-operator repeatability. Reliability and repeatability were evaluated by means of parametric and non-parametric tests, intra-class correlation, the Dahlberg formula, and Bland–Altman plots (p < 0.05). Results: Both reference systems presented good reliability and showed a small difference with respect to the CBCT-based sagittal plane (Sagittal FS1 = 1.90 ± 0.98°; Sagittal FS2 = 1.80 ± 1.13°; p = 0.232). Between them, the two reference systems showed a small difference in the position of the sagittal plane (Sagittal FS1^Sagittal FS2 = 1.39 ± 1.13°). Conclusions: Both reference systems assessed in this study showed good intra-operator repeatability and their use may be suggested as reliable reference systems for FSs.

From masks to muscles: Mapping facial structure of Nycticebus.

Facial musculature in mammals underlies mastication and nonverbal communicative facial displays. Our understanding of primate facial expression comes primarily from haplorrhines (monkeys and apes), while our understanding of strepsirrhine (lemurs and lorises) facial expression remains incomplete. We examined the facial muscles of six specimens from three Nycticebus species (Nycticebus coucang, Nycticebus javanicus, and Nycticebus menagensis) using traditional dissection methodology and novel three-dimensional facial scanning to produce a detailed facial muscle map, and compared these results to another nocturnal strepsirrhine genus, the greater bushbaby (Otolemur spp.). We observed 19 muscles with no differences among Nycticebus specimens. A total of 17 muscles were observed in both Nycticebus and Otolemur, with little difference in attachment and function but some difference in directionality of movement. In the oral region, we note the presence of the depressor anguli oris, which has been reported in other primate species but is absent in Otolemur. The remaining muscle is a previously undescribed constrictor nasalis muscle located on the lateral nasal alar region, likely responsible for constriction of the nares. We propose this newly described muscle may relate to vomeronasal organ functioning and the importance of the use of nasal musculature in olfactory communication. We discuss how this combined methodology enabled imaging of small complex muscles. We further discuss how the facial anatomy of Nycticebus spp. relates to their unique physiology and behavioral ecology.

Modern approach to the treatment of postoperative symptoms of patients undergoing oral surgery

Introduction. Removal of wisdom teeth is always accompanied by the appearance of collateral edema of varying severity, pain, neurological dysfunction and inflammatory contracture of the masticatory muscles.Purpose. To evaluate the use of local apparatus hypothermia and the method of three-dimensional facial scanning for the treatment of patients after extraction of mandibular third molars.Materials and methods. 60 patients had their wisdom teeth removed. Depending on the group, local apparatus hypothermia (LAH) (study group of 30 patients) and local ice hypothermia (LIH) (control group of 30 patients) were performed after surgery. Evaluation criterion: three-dimensional scanning of the face on days 3, 5, 7.Results. In the control group, on the 3rd day the size of the edema was 6.31 mm (SD 0.81), on the 5th day – 4.88 mm (SD 0.73), on the 7th day – 3.44 mm (SD 0.88). In the study group, on the 3rd day the size of the edema was 5.09 mm (SD 0.80), on the 5th day – 2.73 mm (SD 0.71), on the 7th day – 1.28 mm (SD 0,62). In the control group, the size of edema on the 5th day changed by 22.67% compared to the 3rd day, on the 7th day by 30.12% compared to the 5th day and by 45.94% compared to 3rd day. In the study group, the size of edema on the 5th day changed by 46.42% compared to the 3rd day, on the 7th day by 53.16% compared to the 5th day and by 75.32% compared 3rd day. Comparison of groups 3, 5 and 7 in terms of absolute values of edema size and percentage change showed a statistically significant difference (p<0.001).Conclusion. The use of local apparatus hypothermia in the postoperative period can reduce the severity of collateral edema in a shorter period compared to standard methods of local hypothermia.

The Effects of a Cool Saline Solution Irrigation on Mandibular Third Molar Extraction Site: A Postoperative Split-Mouth Evaluation.

This study aimed to evaluate the effects of sterile saline solution irrigation (lavage) performed after mandibular third molar extraction on postoperative complications, utilizing a split-mouth randomized clinical trial design. Seventeen healthy participants requiring bilateral mandibular third molar extraction were enrolled in this single-center study. In each participant, one impacted third molar was designated as the experimental group and subjected to saline lavage at 4 °C. In contrast, the control group was the other impacted third molar, undergoing saline lavage at 25 °C. Various parameters, including postoperative pain, mouth opening, and facial swelling, were assessed using standardized measures and three-dimensional facial scanning at multiple time points. The average age of participants was 26.66 ± 4.1 years, with no postoperative complications observed in either group. The duration of surgery did not significantly differ between groups. Postoperative pain was significantly reduced in the experimental group during the immediate postoperative period compared with the control group, but this difference diminished over time. No significant differences were observed in mouth opening or facial swelling between groups at any time. In site 4 °C, sterile saline solution irrigation after mandibular third molar extraction may effectively reduce early postoperative complications, particularly pain, without prolonging surgical duration.

Does adjunctive fixation in conjunction with miniplate affect condylar position and morphology after mandibular advancement through bilateral sagittal split ramus osteotomy? A retrospective 3-dimensional CT comparative study

To minimize condylar positional and morphological changes after mandibular advancement through bilateral sagittal split ramus osteotomy (BSSRO), surgeons add either a bicortical screw or a two-hole plate distal to the conventional single miniplate. Since there have been no previous studies investigating the effect of this combination, our study aimed to evaluate the short- and long-term effects of these adjunctive fixation methods (AFM) on condylar positional and morphological changes after mandibular advancement through BSSRO.This retrospective cohort study included consecutive patients with retruded mandibles who were treated in the Department of Orthognathic and TMJ Surgery at West China Hospital of Stomatology, Sichuan University. The patients were divided into two groups based on the primary predictor variable, which was the addition of AFM — either a single bicortical screw or a two-hole plate in addition to the single miniplate. The primary outcome variable was the condylar positional and morphological changes after mandibular advancement through BSSRO. Three-dimensional facial CT scans were obtained at three different time points (preoperatively — T0, 1 week postoperatively — T1, and 1 year postoperatively — T2) and analyzed using ITK-SNAP, 3D Slicer, and SlicerSALT software. Intergroup comparisons were conducted with an independent t-test, with a p-value of <0.05 considered significant. Correlations between the variables were estimated by Pearson correlation. The study comprised 51 patients (32 females, 19 males; mean age 25.13 ± 4.24 years), involving a total of 81 condyles (21 unilateral and 60 bilateral).There was a significant difference in long-term condylar displacement in favor of AFM along with a single miniplate (p < 0.001). The bicortical screw group recorded less condylar displacement than the two-hole plate group horizontally (0.11 mm vs 0.22 mm) and sagittally (0.03 mm vs 0.17 mm), but more vertically (0.85 mm vs 0.03 mm). Bone formation associated with AFM occurred on all condylar surfaces, compared with only three surfaces in the single miniplate group.The adjunctive method in addition to the single miniplate fixation method showed less condylar displacement and more bone apposition after mandibular advancement through BSSRO. The follow-up duration variable was the only significant determinant for volumetric changes in the condyle.

Comparison of two 3D scanning software to identify facial features: a prospective instrument to predict difficult airway

BackgroundClinical airway assessment has limited predictive ability to anticipate difficult airway. Three-dimensional (3D) technologies have emerged in medicine as valuable tools in different settings including innovation and surgical planning. Three-dimensional facial scanning could add value to clinical measurements and two-dimensional models to assess the airway. However, commonly used high-fidelity scans are expensive. This study aims to compare the accuracy of the measurements made by the Scandy Pro app as a cost-effective alternative to high-fidelity scans made by the Artec Space Spider. We also aim to evaluate the interobserver variability for the measurements performed with Scandy Pro.Materials and methodsWe conducted a cross-sectional, comparison study on 10 healthy volunteers. Four observers measured 720 distances and 400 using both Scandy Pro and Artec Space Spider facial scans. Wilcoxon test was used for group–group comparison.ResultsComparison of both instruments showed no difference in angle or distance measurements. The percentage error (measurement difference between the two devices) exhibited by one of the observers was significantly different compared with the other three observers; however, the magnitude of this individual deviation did not affect the overall percentage error. The overall error for Scandy Pro was 5.5% (3.9% and 6.7% for angles and distances, respectively).ConclusionThree-dimensional facial scanning with Scandy Pro is an accurate tool that can be a cost-effective alternative to high-fidelity scans produced by the Artec Space Spider.

Validation of low-cost mobile phone applications and comparison with professional imaging systems for three-dimensional facial imaging: A pilot study

PurposeThe objective of this study was to investigate the accuracies of three-dimensional (3D) facial scanning mobile phone applications as compared to professional 3D facial imaging systems. Materials and MethodsA manikin head model was used as the subject for comparing six 3D facial imaging systems which comprised three professional 3D scanners (3dMDface, Artec Eva and Vectra H2) and three mobile phone applications (Bellus3D, ScandyPro and Hedges). For each system, five scans were taken to analyse (1) linear accuracy using 9 measurements (2) global and (3) regional 3D accuracy of the scanned surface by root mean square (RMS) and colour map analysis. Another set of five scans was repeated by a second operator to evaluate the inter-operator reproducibility for each system. ResultsAll the facial imaging systems had absolute errors lesser than 1.0 mm for the linear measurements. The technical error of measurement (TEM) for inter-examiner and intra-examiner linear measurements were within acceptable limits. Artec Eva, Vectra H2 and Scandy Pro had poor global 3D trueness (RMS > 1.0 mm) but good 3D regional trueness (RMS < 1.0 mm). 3dMDface, Bellus3D Face App and Heges had good global and regional 3D trueness. All the facial imaging systems had good global and regional 3D precision and reproducibility (RMS < 1.0 mm). ConclusionThis study demonstrated that mobile phone 3D scanning applications had comparable trueness, precision and reproducibility to professional systems. Colour map analysis supplemented the use of the RMS value to demonstrate facial regions of significant deviation. Clinicians should also consider the specific area or region of inaccuracies for each system to determine whether the chosen system is appropriate for the clinical condition or procedure. Clinical SignificanceMobile phone 3D facial imaging applications may be as accurate as 3D professional facial scanning systems for craniomaxillofacial purposes. However, the choice of the system may vary depending on the specific area of interest.

Geometric morphometrics and machine learning from three-dimensional facial scans for difficult mask ventilation prediction.

Unanticipated difficult mask ventilation (DMV) is a potentially life-threatening event in anesthesia. Nevertheless, predicting DMV currently remains a challenge. This study aimed to verify whether three dimensional (3D) facial scans could predict DMV in patients scheduled for general anesthesia. The 3D facial scans were taken on 669 adult patients scheduled for elective surgery under general anesthesia. Clinical variables currently used as predictors of DMV were also collected. The DMV was defined as the inability to provide adequate and stable ventilation. Spatially dense landmarks were digitized on 3D scans to describe sufficient details for facial features and then processed by 3D geometric morphometrics. Ten different machine learning (ML) algorithms, varying from simple to more advanced, were introduced. The performance of ML models for DMV prediction was compared with that of the DIFFMASK score. The area under the receiver operating characteristic curves (AUC) with its 95% confidence interval (95% CI) as well as the specificity and sensitivity were used to evaluate the predictive value of the model. The incidence of DMV was 35/669 (5.23%). The logistic regression (LR) model performed best among the 10 ML models. The AUC of the LR model was 0.825 (95% CI, 0.765-0.885). The sensitivity and specificity of the model were 0.829 (95% CI, 0.629-0.914) and 0.733 (95% CI, 0.532-0.819), respectively. The LR model demonstrated better predictive performance than the DIFFMASK score, which obtained an AUC of 0.785 (95% CI, 0.710-0.860) and a sensitivity of 0.686 (95% CI, 0.578-0.847). Notably, we identified a significant morphological difference in the mandibular region between the DMV group and the easy mask ventilation group. Our study indicated a distinct morphological difference in the mandibular region between the DMV group and the easy mask ventilation group. 3D geometric morphometrics with ML could be a rapid, efficient, and non-invasive tool for DMV prediction to improve anesthesia safety.

WITHDRAWN: Accuracy and reproducibility of tablet-based applications for three-dimensional facial scanning: an in-vitro study.

This article has been withdrawn at the request ot the author(s).

"Application of the Wilson-Richmond Categorisation Tool on Three-Dimensional Facial Scans of a Population of 12-Year Old Welsh Children"

"Application of the Wilson-Richmond Categorisation Tool on Three-Dimensional Facial Scans of a Population of 12-Year Old Welsh Children"

Accuracy (trueness and precision) of four tablet-based applications for three-dimensional facial scanning: An in-vitro study

ObjectivesThis study aimed to investigate the overall and regional accuracy (trueness and precision) of digital three-dimensional (3D) facial scans obtained from four tablet-based applications, which were (Bellus) the Bellus Dental Pro® (Bellus3D, Inc. Campbell, CA, USA), (Capture) the Capture®: 3D Scan Anything (Standard Cyborg, Inc. San Francisco, CA, USA), (Heges) the Heges® (by Marek Simonik, Ostrava, North Moravia, Czech Republic), and (Scandy) the Scandy Pro 3D Scanner® (Scandy LLC, New Orleans, LA, USA). MethodsA mannequin's face was marked with 63 landmarks. Subsequently, it was scanned 5 times using each scan application on an iPad Pro® (Apple Inc., Cupertino, CA, USA). The digital measurements were obtained with MeshLab® (CNR-ISTI, Pisa, Tuscany, Italy) and compared to the manual measurements using a digital vernier calliper (Truper Herramientas S.A., Colonia Granada, Mexico City, Mexico). The absolute mean difference and the standard deviation of the dimensional discrepancies were calculated. Moreover, the data were analysed by using one-way ANOVA, Levene's test, and Bonferroni´s correction. ResultsThe absolute mean trueness values were Bellus 0.41 ± 0.35 mm, Capture 0.38 ± 0.37 mm, Heges 0.39 ± 0.38 mm, and Scandy 0.47 ± 0.44 mm. Moreover, precision values were Bellus 0.46 mm, Capture 0.46 mm, Heges 0.54 mm, and Scandy 0.64 mm. Comparing the regions, Capture and Scandy showed the highest absolute mean difference, which was 0.81 mm in the Frontal and Zygomaticofacial regions, respectively. ConclusionsThe trueness and precision of all four tablet-based applications were clinically acceptable for diagnosis and treatment planning. Clinical significanceThe future of the three-dimensional facial scan is auspicious, and it has the potential to be affordable, accurate, and of great value for clinicians in their daily practice.

THREE-DIMENSIONAL SCANNING IN RHINOPLASTY AND INDIVIDUAL PATIENT EXPERIENCE

Introduction: Three-dimensional facial scanning has been the object of study for decades and increasingly being used in rhinoplasty, and has recently been applied to surgical simulation. The patient’s perspective in this context should be explored, so that surgeons can individualize their approach. Objectives: Acess the patient’s perspective on three-dimensional scanning in rhinoplasty and their experience during the evaluation and simulation processes in preoperative consultation. Material and methods: Longitudinal, prospective and qualitative study, with the application of a questionnaire to patients who searched for rhinoplasty, during the preoperative consultation after obtaining images through 3D scanning and case simulation. Results: All participants agreed that three-dimensional scanning optimizes patient-surgeon communication; that it should become routine in the preoperative evaluation of cosmetic surgeries; and they felt more confident about the surgery after this process. None of the interviewees mentioned discomfort while obtaining the images. More than 60% were surprised by the images obtained by the three-dimensional facial scanning and by the result of the simulation. Discussion: The use of computerized imaging in the preoperative consultation transforms patients from passive listeners to active participants, who express their intentions and are involved in the discussion of the objectives of the surgery to which they will be submitted. Reservations regarding cost, additional time, and increased patient expectations must be considered. Conclusion: Three-dimensional facial scanning is an additional tool in the rhinoplasty preoperative period, bringing benefits to the communication and relationship between physicians and patients.

The association between dental and facial symmetry in adolescents

Facial aesthetics have become one of the most important objectives of orthodontic treatment. The correction of dental arches should be performed in accordance with the face. This study explored the association between occlusal and facial asymmetries in adolescents, particularly emphasizing a Class II subdivision. Eighty-one adolescents (43 males, 38 females) with a median age of 15.9 (interquartile range, 15.17-16.33) years were enrolled. Of these patients, 30 had a Class II subdivision (right side, n= 12; left side, n= 18). Three-dimensional facial scans were analyzed using surface- and landmark-based methods. Chin asymmetry was determined using the chin volume asymmetry score. Three-dimensional intraoral scans were analyzed to assess occlusal asymmetry. The surface matching scores were 59.0% ± 11.3% for the whole face and 39.0% ± 19.2% for the chin. Chin volume was larger on the right side than on the left side in most patients (n= 51, 63%), and it was associated with a dental midline shift to the corresponding subdivision side. A correlation between dental and facial asymmetries was noted. In addition, the dental midline shifted to the left in patients with a Class II subdivision, regardless of the side, and to the right in those with a symmetrical Class II subdivision. However, several patients did not possess asymmetrical occlusal traits sufficient for statistical analysis. Dental asymmetry was weak but significantly correlated with facial asymmetry.

Three-dimensional evaluation of the association between face and back asymmetry among pre-pubertal subjects.

The aim was to compare the degree of back symmetry in two groups of subjects with and without pathologic facial asymmetry and to assess any possible associations between face and back asymmetry evaluated on three-dimensional surface face and back scans. The study design consisted of allocation of 70 subjects (35 females, 35 males) aged 6.4±0.5 years, according to the percentage of whole face symmetry assessed on three-dimensional (3D) facial scans into a 'symmetric' (symG; symmetry ≥70%) and 'asymmetric'(asymG; symmetry <70%). The 3D face and back scans were analysed using colour deviation maps and percentages of symmetry of the whole face and back surfaces as well as their three separate areas: forehead, maxillary and mandibular areas for the face and neck, upper and middle trunk areas for the back, were calculated. Non-parametric statistical tests were used for between-group comparisons (Mann-Whitney U test). Within each group, differences between each face or back area were tested with the Friedman test. Correlations between face and back symmetry were assessed with the Spearman rho coefficient. The symG exhibited a significantly higher symmetry in each facial area than the asymG. The mandibular area was the least symmetric area of the face within each group, with significantly smaller values than the maxillary area in the symG and significantly smaller values than the forehead and maxillary area in the asymG. The percentage of whole back symmetry did not significantly differ (p>0.05) between the symG ( 82.00% [67.4;88.00]) and asymG (74.3% [66.1;79.6]). The only significant between-group difference was observed for the symmetry of the upper trunk area (p=0.021), with lower symmetry values in the asymG. No significant associations were detected between face and back parameters. The percentages of symmetry in each facial area were significantly higher among subjects without pathologic facial asymmetry. The most asymmetric area of the face, regardless of the degree of whole face symmetry, was its mandibular area. No significant differences were detected within different back areas; however, subjects with asymmetric faces showed significantly smaller symmetry of their upper trunk area.

Development of a Customized Mask Frame Using a Three-Dimensional Facial Scan for an Airtight Seal for Disposable Surgical Face Masks

Abstract Disposable surgical face masks are designed to block the airborne transmission of infectious viruses between patients and healthcare personnel; however, there are limitations to a surgical mask's ability to prevent transmissions because the mask does not provide an airtight seal around the face. This study focuses on the design and development of a custom mask frame, using individuals' three-dimensional (3D) facial scans, to improve the seal of the existing surgical masks. Three participants' facial scans with a wide range of facial dimensions were collected using a 3D hand-held scanner. During design, the contact area between the custom frame and the wearer's skin was determined based on the individual's 3D facial shape. To evaluate the effectiveness of the airtight seal, a qualitative fit (smell/taste) test kit and thermal imaging camera were utilized. When the participants wore the surgical masks without the customized mask frames, the participants smelled the saccharine scent from the test kit. However, while wearing the surgical masks fitted with the custom mask frame that held the mask in place, none of the participants could smell the scent. In addition, thermal images showed ambient temperature changes in the surgical mask suggesting air leakage around the boundary of the mask while the subject was inhaling and exhaling. With the mask frame, thermal images confirmed the effectiveness of the custom frame to block the inflow/outflow of air potentially carrying the virus. The results indicate that the custom-built mask frames are effective in providing a proper and much improved seal compared to a surgical mask without the frame. The developed custom mask frame will be particularly beneficial for frontline medical staff members who treat patients with infectious viruses transmitted through aerosols as part of their PPE.