Accuracy and reliability of automated three-dimensional facial landmarking in medical and biological studies. A systematic review.

BACKGROUND: 3D facial landmarking is becoming a fundamental part of clinical and biological applications. Manual landmarking is time consuming and prone to cumulative errors, so attempts have been made to automate 3D facial landmarking. However, data in the literature are sparse. OBJECTIVES: The objectives of this study are to investigate current evidence for the accuracy and reliability of various 3D facial automated landmarking methods used in medical and biological studies and evaluate their performance against the manual annotation method. SEARCH METHODS: Electronic and manual searches of the literature were performed in April 2021. SELECTION CRITERIA: Only studies that were published in English and evaluated the accuracy of automated landmarking algorithms in 3D facial images for medical or biological settings were included. DATA COLLECTION AND ANALYSIS: Two authors independently screened the articles for eligibility. The QUADAS-2 tool was used for the quality analysis of the included studies. Due to the heterogeneity of the selected studies, a meta-analysis was not possible, so a narrative synthesis of the findings was performed. RESULTS: From 1002 identified records, after applying the inclusion and exclusion criteria, 14 articles were ultimately selected, read, and critically analysed. Different algorithms were used for the automated 3D landmarking of various numbers of facial landmarks ranging from 10 to 29 landmarks. The average difference between the manual and automated methods ranged from 0.67 to 4.73 mm, and the best performance was achieved using deep learning models. Poor study design and inadequate reporting were found in the implementation of the reference standards and population selection for the intended studies, which could have led to overfitting of the tested algorithm. LIMITATIONS: This systematic review was limited by the quality of the included studies and uncovered several methodological limitations evident in the corresponding literature. CONCLUSION AND IMPLICATIONS: Compared to manual landmarking, automated Landmark localization of individual facial landmarks reported in the literature is not accurate enough to allow their use for clinical purposes. This result indicates that automatic facial landmarking is still developing, and further studies are required to develop a system that could match or exceed the performance of the current gold standard. REGISTRATION: PROSPERO: CRD42021241531.

The Validation of an Innovative Method for 3D Capture and Analysis of the Nasolabial Region in Cleft Cases.

OBJECTIVE: To validate a newly developed method for capturing 3-dimensional (3D) images of the nasolabial region for assessing upper lip scarring and asymmetry in surgically managed unilateral cleft lip and palate (UCLP) cases. DESIGN: Validation study, single cohort. MATERIALS AND METHODS: Eighteen surgically managed UCLP cases were recruited, the nasolabial region of each face was scanned using an intraoral scanner (IOS) to produce 3D images. The images were manually segmented to allow the calculation of surface area of the scar and upper lip asymmetry. Five professionals and 5 lay assessors subjectively evaluated the same images and graded the upper lip scarring and asymmetry at 2 separate occasions. The relationship between the subjective and objective assessments was evaluated. RESULTS: Moderate correlation was found between subjective and objective evaluations of the upper lip scarring and total asymmetry. The captured 3D images were of good quality for the objective measurements of lip asymmetry and residual scarring. Moderate to strong correlations were detected between the 2 panels (T ranging between 0.5 and 0.9) with no significant difference (P > .05) in the mean score of the subjectively evaluated parameters. CONCLUSION: The IOS is a useful tool for the capture of the nasolabial morphology. The captured 3D images are a reliable source for measuring lip asymmetry and scar surface area. The method has sufficient validity for routine clinical use and for objective outcome measures of the surgical repair of cleft lip.

An Innovative Assessment of the Dynamics of Facial Movements in Surgically Managed Unilateral Cleft Lip and Palate Using 4D Imaging.

OBJECTIVE: Assess facial asymmetry during maximum smile in patients with surgically managed unilateral cleft lip and palate (UCLP), using a dynamic 3-dimensional (3D) imaging (4-dimensional) system. DESIGN: Prospective 2 cohort comparative study. METHODS: Twenty-five surgically managed UCLP cases and 75 controls at 8 to 10 years of age were recruited. Facial movements during maximum smile were recorded using video stereophotogrammetry at a rate of 60 3D facial images per second. Maximum smile took approximately 3 seconds and generated 180 3D facial images for the analysis. A generic facial mesh which consists of more than 7000 quasi landmarks was used for the assessment of facial asymmetry at 5 key 3D frames representing the pattern of maximum smile. RESULTS: Statistically significant differences were seen regarding the magnitude of facial asymmetry between the UCLP group and the noncleft controls. Higher average asymmetry in the UCLP group was seen in the 3D frame midway between maximum smile and rest (frame 4) followed by the frame at peak expression of maximum smile (frame 3). The average magnitude of nasolabial asymmetry of the control group was within 0.5 mm in comparison with the UCLP cases which was about 1.8 mm. CONCLUSION: This study provided for the first time, an objective tool for analysis of the dynamics of muscle movements which provided an unprecedented insight into the anatomical basis of the residual dysmorphology. The research demonstrates the limitations of the primary lip repair in achieving symmetrical results and underpins the required refinements to improve the quality of surgical repair of cleft lip.

Longitudinal 3D Assessment of Facial Asymmetry in Unilateral Cleft Lip and Palate.

OBJECTIVE: Longitudinal evaluation of asymmetry of the surgically managed unilateral cleft lip and palate (UCLP) to assess the impact of facial growth on facial appearance. DESIGN: Prospective study. SETTING: Glasgow Dental Hospital and School, University of Glasgow, United Kingdom. PATIENTS: Fifteen UCLP infants. METHOD: The 3-D facial images were captured before surgery, 4 months after surgery, and at 4-year follow-up using stereophotogrammetry. A generic mesh which is a mathematical facial mask that consists of thousands of points (vertices) was conformed on the generated 3-D images. Using Procustean analysis, an average facial mesh was obtained for each age-group. A mirror image of each average mesh was mathematically obtained for the analysis of facial dysmorphology. Facial asymmetry was assessed by measuring the distances between the corresponding vertices of the original and the mirror copy of the conformed meshes, and this was displayed in color-coded map. RESULTS: There was a clear improvement in the facial asymmetry following the primary repair of cleft lip. Residual asymmetry was detected around the nasolabial region. The nasolabial region was the most asymmetrical region of the face; the philtrum, columella, and the vermillion border of the upper lip showed the maximum asymmetry which was more than 5 mm. Facial growth accentuated the underlying facial asymmetry in 3 directions; the philtrum of the upper lip was deviated toward the scar tissue on the cleft side. The asymmetry of the nose was significantly worse at 4-year follow-up ( P < .05). CONCLUSION: The residual asymmetry following the surgical repair of UCLP was more pronounced at 4 years following surgery. The conformed facial mesh provided a reliable and innovative tool for the comprehensive analysis of facial morphology in UCLP. The study highlights the need of refining the primary repair of the cleft and the potential necessity for further corrective surgery.

Replacement of the Distorted Dentition of the Cone-Beam Computed Tomography Scans for Orthognathic Surgery Planning.

PURPOSE: Cone-beam computed tomography (CBCT) does not record dental morphology accurately because of the scattering produced by metallic restorations and the reported magnification of the dentition. The aim of this study was the development and evaluation of a new method for the replacement of the distorted dentition of CBCT scans with a 3-dimensional (3D) dental image captured by a digital intraoral camera. MATERIALS AND METHODS: Six dried skulls with orthodontic brackets fixed on the teeth were used in this study. Three intraoral markers made of dental stone were constructed and attached to orthodontic brackets. The skulls were scanned by CBCT and the occlusal surfaces were captured using the TRIOS 3D intraoral scanner. The digital intraoral scan (IOS) was fused into the CBCT models. This produced a new composite digital model of the skull and the dentition. The skulls were scanned again using the commercially accurate Faro laser arm to produce the 3D model the skull and teeth gold standard for the assessment of the accuracy of the developed method. This was assessed by measuring the distance between the occlusal surfaces of the new composite model and the gold standard 3D laser produced model. RESULTS: The results showed the errors related to the superimposition of the intraoral image on the CBCT to replace the distorted dentition were 0.11 to 0.20 mm. CONCLUSION: The results of this novel method suggest that the dentition on the CBCT scan can be accurately replaced with the digital IOS image captured by an intraoral scanner to create a composite model that will improve the accuracy of digital orthognathic surgical planning and the fabrication of the guiding occlusal wafer.

Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study.

BACKGROUND AND PURPOSE: There is limited literature discussing the three dimnesional (3D) impact of rapid maxillary expansion (RME) on upper airway. The purpose of this prospective Cone Beam Computerised Tomography (CBCT) based study is to assess the immediate 3D effects and to correlate the volumteric changes in the upper naspharyngeal airway spaces secondary to RME. MATERIALS AND METHODS: Seventeen participants (8 male, 9 female, with a mean age of 12.6 ± 1.8 years), who required RME for the management of narrow maxillary arch, were recruited for this study. The prescribed expansion regimen was quarter turn (0.25 mm), twice a day until over-expansion was achieved. The mean period for the active phase was 14 days with a range of 12-21 days. Pretreatment (T1) and immediate post-expansion (T2) CBCT images were obtained and then processed using ITK snap and OnDemand3D softwar packages. Paired t-test and Interclass Correlation Coefficient (ICC) were used to assess the reproducibility of the measurements, student t-test (P < 0.05) and Pearson Correlation Coefficient (PCC) were applied to evaluate the volumetric changes in the nasopharyngeal airway spaces, linear dentolaveolar changes and correlate these changes. MAIN FINDINGS: Though, the data of one patient was excluded from the study, owing to major differences (>5 degrees) in the head and neck posture between T1 and T2 CBCT scans, the study' findings shows that bonded RME is an effective dentoalveolar expander in growing patients (P= 0.01) with an average expansion of 3.7 mm and 2.8 mm in males and females respectively. Likewise, the upper nasopharynx (UNP) expanded significantly (15.2% in males and 12% in females). In comparison, the upper retropalatal space (URP) was significantly reduced, by almost one sixth of its original volume, more in males than females, 11.2% and 2.8% respectively. A strong direct correlation between the maxillary sinus volumetric changes, and between appliance expansion and dentoalveolar expansion were evident (PCC = 0.86, 0.75, respectively). There was also a moderate correlation between changes in the UNP and URP spaces. CONCLUSIONS: RME was found to be an effective dentoalveolar expander and significantly augment the UNP and minimize the URP space. A similar comparative clinical study with long-term follow-up would be beneficial in accurately deteremining the clinical impact of RME on the airway and breathing as well as the stability of these effects.

Finite Element Analysis of porously punched prosthetic short stem virtually designed for simulative uncemented Hip Arthroplasty.

BACKGROUND: There is no universal hip implant suitably fills all femoral types, whether prostheses of porous short-stem suitable for Hip Arthroplasty is to be measured scientifically. METHODS: Ten specimens of femurs scanned by CT were input onto Mimics to rebuild 3D models; their *stl format dataset were imported into Geomagic-Studio for simulative osteotomy; the generated *.igs dataset were interacted by UG to fit solid models; the prosthesis were obtained by the same way from patients, and bored by punching bears designed by Pro-E virtually; cements between femora and prosthesis were extracted by deleting prosthesis; in HyperMesh, all compartments were assembled onto four artificial joint style as: (a) cemented long-stem prosthesis; (b) porous long-stem prosthesis; (c) cemented short-stem prosthesis; (d) porous short-stem prosthesis. Then, these numerical models of Finite Element Analysis were exported to AnSys for numerical solution. RESULTS: Observed whatever from femur or prosthesis or combinational femora-prostheses, "Kruskal-Wallis" value p > 0.05 demonstrates that displacement of (d) ≈ (a) ≈ (b) ≈ (c) shows nothing different significantly by comparison with 600 N load. If stresses are tested upon prosthesis, (d) ≈ (a) ≈ (b) ≈ (c) is also displayed; if upon femora, (d) ≈ (a) ≈ (b) < (c) is suggested; if upon integral joint, (d) ≈ (a) < (b) < (c) is presented. CONCLUSIONS: Mechanically, these four sorts of artificial joint replacement are stabilized in quantity. Cemented short-stem prostheses present the biggest stress, while porous short-stem & cemented long-stem designs are equivalently better than porous long-stem prostheses and alternatives for femoral-head replacement. The preferred design of those two depends on clinical conditions. The cemented long-stem is favorable for inactive elders with osteoporosis, and porously punched cementless short-stem design is suitable for patients with osteoporosis, while the porously punched cementless short-stem is favorable for those with a cement allergy. Clinically, the strength of this study is to enable preoperative strategy to provide acute correction and decrease procedure time.

Effects of Le Fort I Osteotomy on the Nasopharyngeal Airway-6-Month Follow-Up.

PURPOSE: The literature discussing the impact of a single Le Fort I osteotomy on nasopharyngeal airways is limited. This study assessed the volumetric changes in the nasopharyngeal airway after a single Le Fort I osteotomy and explored the correlation between these changes and 3-dimensional surgical movements of the upper jaw. MATERIALS AND METHODS: This retrospective study was conducted in 40 patients who had undergone a single Le Fort I (maxillary advancement with or without impaction) to correct Class III malocclusion with maxillary hypoplasia. Preoperative (T1) and 6-month postoperative (T2) cone-beam computed tomographic (CBCT) scans of these patients were used for analysis. Maxillary surgical movements and volumetric changes in the nasopharyngeal airway were measured. The reproducibility of the measurements was evaluated using paired t tests and intraclass correlation coefficients. The Wilcoxon test and Pearson correlation coefficient were applied to evaluate the volumetric changes in the nasopharyngeal airway space and assess the correlations of these changes to the maxillary surgical movements. RESULTS: Six patients were excluded from the study owing to major differences (>5°) in their head and neck posture between the T1 and T2 CBCT scans. The errors of the repeated measurements were insignificant (P > .05), with a high level of agreement (r = 0.99; P < .05) between the repeated digitization of the landmarks. There was a statistically significant impact of a Le Fort I osteotomy on the right maxillary sinus (decreased by 17.8%) and the lower retropalatal space (expanded by 17.3%; P < .05). The correlation between the change in airway volume and the magnitude of surgical maxillary movements was moderate (r = .4). Similarly, there was a moderate correlation between changes in the upper nasopharynx and those in the hypopharynx. CONCLUSION: The single Le Fort I osteotomy was found to increase the retroglossal airway volume. This could be important for the treatment of obstructive sleep apnea in patients with maxillary deficiency. A long-term follow-up assessment of a larger sample with a functional assessment of airway would be beneficial to confirm these findings.

Evaluation of the Reproducibility of Nonverbal Facial Expressions Using a 3D Motion Capture System.

OBJECTIVE: To evaluate the reproducibility of three nonverbal facial expressions using a three-dimensional motion capture system. DESIGN: Prospective, cross-sectional, controlled study. SETTING: Glasgow Dental Hospital and School, University of Glasgow, United Kingdom. PATIENTS AND PARTICIPANTS: Thirty-two subjects, 16 males and 16 females. METHODS: With a three-dimensional video passive stereophotogrammetry imaging system, maximal smile, cheek puff, and lip purse were captured for each subject. Anatomical facial landmarks were digitized on the first frame and then tracked automatically. The same facial expressions were captured 15 minutes later. MAIN OUTCOME MEASURES: The magnitude of each expression and speed of landmark displacement were calculated. The landmark motion curves were spatially and temporally aligned to calculate the similarity of the dynamic movements of the same landmarks between the captures. RESULTS: There were no significant differences between individuals for magnitude (P = .892) or for speed (P = .456). There were significant differences in landmark movement similarity (P = .011); similarity was more reproducible for maximal smile. There was no significant gender effect on the difference in magnitude. There was a significant gender effect on speed to reach maximal smile (P = .044) and a pursed-lip expression (P = .038). There was a significant gender effect on landmark movement similarities (P = .031) for cheek puff expression. CONCLUSIONS: There were no differences in magnitude and speed for maximal smile, cheek puff, and lip purse between the two captures for all participants. For individual expressions, maximal smile expression had the highest similarity value for individual landmarks.

The Impact of Orthognathic Surgery on Facial Expressions.

PURPOSE: The aim of this study was to evaluate the impact of orthognathic surgical correction of facial asymmetry and maxillary hypoplasia on the magnitude and pattern of facial expressions. PATIENTS AND METHODS: This study was carried out on 2 cohorts of patients: in group 1, 10 patients had surgical correction of facial asymmetry; in group 2, 13 patients had Le Fort I osteotomy to correct maxillary hypoplasia. The patients were asked to perform 3 facial expressions (maximal smile, lip purse, and cheek puff) that were recorded using the Di4D image-capture system before and after surgery. The capture of each expression generated 180 3-dimensional (3D) facial images. Twenty-seven facial soft tissue landmarks were digitized on the first frame of the 3D image of each expression and a mathematical generic mesh was applied on the 3D model to clone each patient's face. The cloned mesh was superimposed automatically on each sequence of the 3D images to evaluate the pattern of facial expressions. The digitization of facial landmarks was satisfactorily accurate and reproducible. RESULTS: In group 1, the asymmetry of facial expressions was significantly decreased after surgical correction (P = .0458). In group 2, Le Fort I osteotomy decreased the magnitude of facial expressions (P = .0267). CONCLUSION: This study confirmed that orthognathic surgery affects the dynamics of facial expressions; this should be considered when planning the surgery and informing patients about the surgical correction of dentofacial deformities.

Survey of Plant Drought-Resistance Promoting Bacteria from Populus euphratica Tree Living in Arid Area.

Two hundred and thirty-two bacterial strains were isolated from the rhizospheric soil of Populus euphratica which is the dominant tree living in extreme arid regions in northwest China. Some strains with plant growth-promoting bacteria related metabolic characteristics were able to promote drought resistance in plants after inoculation. Ten strains with the greatest effects increased the dry weight of wheat shoots from 0.5 to 34.4 %, and the surface area of the root systems from 12.56 to 212.17 % compared to the control after drought treatment whereas no obvious promoting effect was observed in normal water conditions. These 10 strains were identified to be of the genera Pseudomonas, Bacillus, Stenotrophomonas and Serratia by 16S rRNA (rrs) gene sequence alignment. Among these strains, Serratia sp. 1-9 and Pseudomonas sp. 5-23 were the two most effective strains. Both of them produced auxin and the production increased significantly when cultured under simulated drought conditions which are inferred to be the most plausible mechanism for their plant growth-promoting effect under drought stress.

Dynamics analysis for flexion and extension of elbow joint motion based on musculoskeletal model of Anybody.

PURPOSE: Little is known about how biomechanics governs the biological nature for humeral motion dynamically. Elbow motion ought to be investigated based on a musculoskeletal model and evidence the physiologic principle of upper limbs. METHOD: A humeral model was reconstructed by MIMICS after CT images input in *.dicom format, it was processed by Geomagic Studio for Surfaces, then gridded mesh and assigned materials by Hypermesh. On the other hand, a musculoskeletal model was built by AnyBody, physical motions were then simulated to export boundary condition and myodynamia during flexion and extension. Finally, all the humeral model and boundary were imported to Abaqus for finite element analysis. RESULT: During the simulative motion of flexion, the primary muscles are brachii biceps, brachialis anticus and teretipronator, their myodynamia increased and then decreased gradually, and reached its peak value at 30°; During extension, the main muscles are triceps brachii and brachialis anticus, their myodynamia increased and then decreased gradually too, and reached peak at 50°; In these two cases, their strain and displacement distributed at the middle of humerus. CONCLUSION: AnyBody is a novel modelling system to simulate physical motion, for example flexion and extension. Biceps brachii and brachialis anticus are functional for flexion, and triceps brachii plays a key role in extension critically. This simulation confirms the physiologic rule for sport event, humeral fixation and postoperative healing with clinical significance that minimizing joint forces from injury onset may promote pain-free ways.

Dynamic effect of three locking plates fixated to humeral fracture based on multibody musculoskeletal model.

OBJECTIVE: This study attempts to analyse the biomechanical effect of internal fixation (plated in parallel or plated vertically) on the basis of distal humeral fractures on musculoskeletal multibody dynamics using AnyBody in Finite Element Method. METHOD: Humeral 3D models were reconstructed by MIMICS after volunteers' CT image input in *.dicom format, and processed by Geomagic Studio for surfaces, while locking plates and screws were then designed by Pro-E. A humeral model of T-type fracture was created and assembled in Hypermesh, to integrate fixtures (e.g., MPL/PML/ML), to grid the mesh and then assign materials. A musculoskeletal model of the upper limb was established by AnyBody to simulate elbow flexion and extension. They were finally imported to Abaqus for boundary conditions and dynamic analysis. RESULT: In terms of Von Mises stress, its maximum increased and then decreased gradually during the joint motion, but p > 0.05 in SPSS suggests no significant difference for all three fixtures. In terms of displacement, when the elbow was at 90°, each motional pattern reached its peak as follows: ML180° = 0.28 mm, MPL90° = 0.49 mm & PML90° = 0.54 mm during flexion; ML180° = 0.073 mm, MPL90° = 0.10 mm & PML90° = 0.12 mm during extension. p < 0.05 suggests a significant difference for the displacements of all three fixations. p = 0.007 < 0.01667 suggests the significant difference between the two fixations, for example, PML90° and ML180°, indicating that the peak displacement of ML180° is less than that of PML90°. CONCLUSION: After generally analysed in musculoskeletal dynamics, the biomechanical property of the fixtures was presented as follows: the displacement of the parallel plate was less than that of the vertical, and the parallel plate may optimise the clinical reduction anatomically.

The Characterisation of the Craniofacial Morphology of Infants Born With Zika Virus; Innovative Approach for Public Health Surveillance and Broad Clinical Applications.

Background: This study was carried out in response to the Zika virus epidemic, which constituted a public health emergency, and to the 2019 WHO calling for strengthened surveillance for the early detection of related microcephaly. The main aim of the study was to phenotype the craniofacial morphology of microcephaly using a novel approach and new measurements, and relate the characteristics to brain abnormalities in Zika-infected infants in Brazil to improve clinical surveillance. Methods: 3D images of the face and the cranial vault of 44 Zika-infected infants and matched healthy controls were captured using a 3D stereophotogrammetry system. The CT scans of the brain of the infected infants were analysed. Principal component analysis (PCA) was applied to characterise the craniofacial morphology. In addition to the head circumference (HC), a new measurement, head height (HH), was introduced to measure the cranial vault. The level of brain abnormality present in the CT scans was assessed; the severity of parenchymal volume loss and ventriculomegaly was quantified. Student's t-test and Spearman's Rho statistical test have been applied. Findings: The PCA identified a significant difference (p < 0.001) between the cranial vaults and the face of the Zika infants and that of the controls. Spearman's rank-order correlation coefficients show that the head height (HH) has a strong correlation (0.87 in Zika infants; 0.82 in controls) with the morphology of the cranial vaults, which are higher than the correlation with the routinely used head circumference (HC). Also, the head height (HH) has a moderate negative correlation (-0.48) with the brain abnormalities of parenchymal volume loss. Interpretation: It is discovered that the head height (HH) is the most sensitive and discriminatory measure of the severity of cranial deformity, which should be used for clinical surveillance of the Zika syndrome, evaluation of other craniofacial syndromes and assessment of various treatment modalities.

Comparative analysis for five fixations of Pauwels-I by the biomechanical finite-element method.

Background: Little is known about how biomechanics govern the five fixtures such as DHS, MLS, DHS + LS, LP, and HA are accepted as common therapeutic techniques. Aims and objectives: A series of numerical models for a femoral neck fracture of Pauwels-I will be constructed by innovative approach of finite element in order to determine the most optimized option in comparison with biomechanical performance. Method: Twenty sets of computer tomography scanned femora were imported onto Mimics to extract 3 D models; these specimens were transferred to Geomagic-Studio for a simulative osteotomy and kyrtograph; then, they underwent UG to fit simulative solid models; 5 sorts of fixture were then expressed by Pro-Engineer virtually. After processing with HyperMesh, all compartments (fracture model + internal implant) were assembled onto 5 systems: "Dynamic Hip Screw (DHS), Multiple Lag screw (MLS), DHS + LS, femoral Locking Plate (LP) and HemiArthroplasty (HA)." Eventually, numerical models of the finite-elemental analysis were exported to AnSys to determine the solution. Result: Four models of fixation and a simulation of HA for Pauwels-I were established, validated, and analyzed with the following findings: In term of displacement, these 5 fixtures ranged between 0.3801 and 0.7536 mm have no significant difference; in term of stress, the averages of peaks for integral assemblage are b(MLS) = 43.5766 ≈< d(LP) = 43.6657 ≈< e(Ha) = 43.6657 < c(DHS + LS) = 66.5494 < a(DHS) = 105.617 in MPa indicate that MLS, LP and HA are not significantly different, but less than DHS + LS or DHS in each. Conclusion: A fixture of MLS or LP with optional HA should be recommended to clinically optimize a Pauwels-I facture.

Assessment of regional asymmetry of the face before and after surgical correction of unilateral cleft lip.

This study was carried out on 26 unilateral cleft lip and palate (UCLP) cases with mean age 3.6 ± 0.7 months.3D facial images were captured for each infant 2-3 days before the repair of cleft lip and at 4 months following surgery at a mean age of 8.2 ± 1.8 months, using a stereophotogrammetry imaging system. An iterative closest point (ICP) algorithm was used to superimpose the 3D facial model to its mirror image using VRMesh software. After the superimposition, the face model was divided into seven anatomical regions. Asymmetry of the entire face and of the anatomical regions was calculated by measuring the absolute distances between the 3D facial surface model and its mirror image. Colour maps were used to illustrate the patterns and magnitude of the facial asymmetry before and after surgery. There were significant decreases in the asymmetry scores for the nose, upper lip and the cheeks as a result of the surgical repair of cleft lips. Surgery did not change the magnitude of the asymmetry scores for the lower lip and chin. Residual nasolabial asymmetries were detected. The main outcome of the findings of this innovative study is to inform the required surgical refinement of primary repair of cleft lip in order to minimise facial asymmetry. We have presented a sensitive tool that could be used for comparative analysis of lip repair at various cleft centres and to guide secondary corrective surgery when required.

Clinical Monitoring of Tooth Wear Progression in Patients over a Period of One Year Using CAD/CAM.

PURPOSE: The aim of this study was to clinically monitor the progression of tooth wear over a period of 1 year in a cohort of referred tooth wear patients through the use of a computer-aided design/computer-assisted manufacture (CAD/CAM) scanner and a standardized scanning/assessment methodology. MATERIALS AND METHODS: Polyether impressions were made of 11 participants (130 teeth) at baseline and at 1 year. Impressions were poured in type IV dental stone and the anterior teeth were 3D scanned. A surface-matching software was used to compare 1-year and baseline scans and identify any dimensional differences. RESULTS: Parafunctional habits were reported by all patients. All participants exhibited tooth wear ≥ 140 µm in depth and extending to ≥ 280 µm in at least one tooth. Maxillary central incisors were the most commonly and severely affected teeth. CONCLUSION: The ability of the developed CAD/CAM scanning methodology in clinical monitoring of tooth wear was demonstrated. Further research is needed to assess its practicality in large-scale epidemiologic tooth wear studies.

Multi-view stereophotogrammetry for post-mastectomy breast reconstruction.

A multi-view three-dimensional stereophotogrammetry system was developed to capture 3D shape of breasts for breast cancer patients. The patients had received immediate unilateral breast reconstruction after mastectomy by the extended latissimus dorsi flap and without contralateral surgery. In order to capture the whole breast shape including the inframammary fold, the patients were introduced to the imaging room and leaned over the imaging rig to open up the inframammary fold and to expose the entire area of each breast. The imaging system consisted of eight high-resolution ([Formula: see text] pixels) digital cameras and four flash units. The cameras were arranged in four stereo pairs from four different view angles to cover the whole surface of the breasts. The system calibration was carried out ahead of every capture session, and the stereo images were matched to generate four range images to be integrated using an elastic model proposed. A watertight breast mesh model was reconstructed to measure the volume of the breast captured. The accuracy of using the developed multi-view stereophotogrammetry system for breast volume measurement was 11.12cc with SEM 7.74cc, comparing to the measurements of the water displacement method. It was concluded that the 3D stereophotogrammetry image system developed was more reliable than the method of water displacement.

A Proposed Methodology to Assess the Accuracy of 3D Scanners and Casts and Monitor Tooth Wear Progression in Patients.

PURPOSE: The aim of this study was to detail and assess the capability of a novel methodology to 3D-quantify tooth wear progression in a patient over a period of 12 months. MATERIALS AND METHODS: A calibrated stainless steel model was used to identify the accuracy of the scanning system by assessing the accuracy and precision of the contact scanner and the dimensional accuracy and stability of casts fabricated from three different types of impression materials. Thereafter, the overall accuracy of the 3D scanning system (scanner and casts) was ascertained. Clinically, polyether impressions were made of the patient's dentition at the initial examination and at the 12-month review, then poured in type IV dental stone to assess the tooth wear. The anterior teeth on the resultant casts were scanned, and images were analyzed using 3D matching software to detect dimensional variations between the patient's impressions. RESULTS: The accuracy of the 3D scanning system was established to be 33 µm. 3D clinical analysis demonstrated localized wear on the incisal and palatal surfaces of the patient's maxillary central incisors. The identified wear extended to a depth of 500 µm with a distribution of 4% to 7% of affected tooth surfaces. CONCLUSION: The newly developed 3D scanning methodology was found to be capable of assessing and accounting for the various factors affecting tooth wear scanning. Initial clinical evaluation of the methodology demonstrates successful monitoring of tooth wear progression. However, further clinical assessment is needed.

The Accuracy of Conformation of a Generic Surface Mesh for the Analysis of Facial Soft Tissue Changes.

PURPOSE: Three dimensional analysis of the face is required for the assessment of complex changes following surgery, pathological conditions and to monitor facial growth. The most suitable method may be "dense surface correspondence". MATERIALS AND METHODS: This method utilizes a generic facial mesh and "conformation process" to establish anatomical correspondences between two facial images. The aim of this study was to validate the use of conformed meshes to measure simulated maxillary and mandibular surgical movements. The "simulation" was performed by deforming the actual soft tissues of the participant during image acquisition. The study was conducted on 20 volunteers and used 77 facial landmarks pre-marked over six anatomical regions; left cheek, right cheek, left upper lip, philtrum, right upper lip and chin region. Each volunteer was imaged at rest and after performing 5 different simulated surgical procedures using 3D stereophotogrammetry. The simulated surgical movement was determined by measuring the Euclidean distances and the mean absolute x, y and z distances of the landmarks making up the six regions following digitization. A generic mesh was then conformed to each of the aligned six facial 3D images. The same six regions were selected on the aligned conformed simulated meshes and the surgical movement determined by determining the Euclidean distances and the mean absolute x, y and z distances of the mesh points making up the six regions were determined. RESULTS: In all cases the mean Euclidian distance between the simulated movement and conformed region was less than 0.7 mm. For the x, y and z directions the majority of differences in the mean absolute distances were less than 1.0mm except in the x-direction for the left and right cheek regions, which was above 2.0 mm. CONCLUSIONS: This concludes that the conformation process has an acceptable level of accuracy and is a valid method of measuring facial change between two images i.e. pre- and post-surgery. The conformation accuracy is higher toward the center of the face than the peripheral regions.