A vision-based three-dimensional capture system for maxillofacial assessment and surgical planning

Accuracy of three-dimensional virtual simulation of the soft tissues of the face in OrtogOnBlender for correction of class II dentofacial deformities: an uncontrolled experimental case-series study

Purpose

To assess whether virtual simulations of the projection of the soft tissues of the face after class II bimaxillary orthognathic surgery, generated from 3D reconstruction of preoperative computed tomography (CT) scans, differed significantly from the actual soft tissue profile obtained in the late postoperative period (beyond 6 months). Secondarily, to validate the accuracy of a free, open-source software suite for virtual soft tissue planning in orthognathic surgery.

Methods

Helical CT scans were obtained pre- and postoperatively from 16 patients with Angle class II malocclusion who underwent bimaxillary orthognathic surgery. A comparative study between soft tissue meshes constructed for surgical simulation (M1) and the actual meshes obtained from postoperative scans (M2) was then performed. To establish the accuracy of 3D facial soft tissue simulation in a free and open-source software suite (OrtogOnBlender-OOB), 17 predetermined anatomic landmarks were measured in M1 and M2 scans after alignment of cranial structures.

Results

The mean error between preoperative simulations and actual postoperative findings was < 2 mm for all anthropometric landmarks. The overall average error for the facial soft tissues was 1.07 mm.

Conclusion

Comparison between preoperative simulation (M1) and actual postoperative findings (M2) showed clinically relevant ability of the method to reproduce actual surgical movement reliably (< 2-mm error). OOB is capable of accurate soft tissue planning for orthognathic surgery, but mesh deformation methods still require improvement.

Trial registration

RBR-88jff9. Retrospectively registered at Brazilian Registry of Clinical trials-ReBec (http://www.ensaiosclinicos.gov.br) May 06, 2020.

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.

Three-Dimensional Imaging in Orthodontics

Orthodontic records are one of the main milestones in orthodontic therapy. Records are essential not only for diagnosis and treatment planning but also for follow-up of the case, communicating with colleagues, and evaluating the treatment outcomes. Recently, two-dimensional (2D) imaging technology, such as cephalometric and panoramic radiographs and photographs, and plaster models were routinely used. However, after the introduction of three-dimensional (3D) technologies (laser scanner, stereophotogrammetry, and computed tomography) into dentistry, 3D imaging systems are more and more commonly preferred than 2D, especially in cases with craniofacial deformities. In fact, 3D imaging provided more detailed and realistic diagnostic information about the craniofacial hard as well as soft tissue and allowed to perform easier, faster, and more reliable 3D analyses. The purpose of this review is to provide an overview of the 3D imaging techniques, including their advantages and disadvantages, and to outline the indications for 3D imaging.

Long-Term Effect of Maxillary Distraction Osteogenesis (DO) on Nasal Index in Adult Patients with Cleft Lip and Palate Deformities

PURPOSE

To test the hypothesis that there is no immediate and long-term effects of maxillary distraction osteogenesis (DO) on nasal index among adult subjects with cleft lip and palate deformities.

MATERIALS AND METHODS

Twelve adult subjects in the age range of 17-20 years with complete unilateral cleft lip and palate underwent advancement of maxilla by DO. The immediate and long-term effects of maxillary DO on nasal index were evaluated from extra-oral full face frontal photographs recorded prior to DO (T0), at the end of active DO (T1) and at least 2-years after the DO (T2). The ANOVA, Post Hoc test (Bonferroni) and Pearson correlation coefficients were used. The probability value (P value) 0.05 was considered as statistically significant.

RESULTS

SNM angle and Ptm-M distance increased significantly by DO (P < 0.001). The nasal index increased significantly (P < 0.01) by 13.85 % from T0 value of 85.15 ± 4.49 to 99.02 ± 11.16 % at the end of active distraction (T1) and by 12.69 to 97.84 ± 9.14 % at the end of long-term follow-up (T2). The correlation between sagittal maxillary advancement and nasal index was statistically significant (P < 0.001). For each millimeter of maxillary advancement, the nasal index increased by 1.38 % and 1.8 % at the end of active distraction and long-term follow-up respectively.

CONCLUSION

The advancement of maxilla by distraction osteogenesis among subjects with cleft lip and palate deformities increased nasal index significantly.

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.

Development of a Three-Dimensional Hand Model Using Three-Dimensional Stereophotogrammetry: Assessment of Image Reproducibility

Purpose

Using three-dimensional (3D) stereophotogrammetry precise images and reconstructions of the human body can be produced. Over the last few years, this technique is mainly being developed in the field of maxillofacial reconstructive surgery, creating fusion images with computed tomography (CT) data for precise planning and prediction of treatment outcome. Though, in hand surgery 3D stereophotogrammetry is not yet being used in clinical settings.

Methods

A total of 34 three-dimensional hand photographs were analyzed to investigate the reproducibility. For every individual, 3D photographs were captured at two different time points (baseline T0 and one week later T1). Using two different registration methods, the reproducibility of the methods was analyzed. Furthermore, the differences between 3D photos of men and women were compared in a distance map as a first clinical pilot testing our registration method.

Results

The absolute mean registration error for the complete hand was 1.46 mm. This reduced to an error of 0.56 mm isolating the region to the palm of the hand. When comparing hands of both sexes, it was seen that the male hand was larger (broader base and longer fingers) than the female hand.

Conclusions

This study shows that 3D stereophotogrammetry can produce reproducible images of the hand without harmful side effects for the patient, so proving to be a reliable method for soft tissue analysis. Its potential use in everyday practice of hand surgery needs to be further explored.

Noninvasive computerized scanning method for the correlation between the facial soft and hard tissues for an integrated three-dimensional anthropometry and cephalometry

OBJECTIVES

The article describes a new methodology to scan and integrate facial soft tissue surface with dental hard tissue models in a three-dimensional (3D) virtual environment, for a novel diagnostic approach.The facial and the dental scans can be acquired using any optical scanning systems: the models are then aligned and integrated to obtain a full virtual navigable representation of the head of the patient.

METHODS

In this article, we report in detail and further implemented a method for integrating 3D digital cast models into a 3D facial image, to visualize the anatomic position of the dentition. This system uses several 3D technologies to scan and digitize, integrating them with traditional dentistry records. The acquisitions were mainly performed using photogrammetric scanners, suitable for clinics or hospitals, able to obtain high mesh resolution and optimal surface texture for the photorealistic rendering of the face. To increase the quality and the resolution of the photogrammetric scanning of the dental elements, the authors propose a new technique to enhance the texture of the dental surface.

RESULTS

Three examples of the application of the proposed procedure are reported in this article, using first laser scanning and photogrammetry and then only photogrammetry. Using cheek retractors, it is possible to scan directly a great number of dental elements. The final results are good navigable 3D models that integrate facial soft tissue and dental hard tissues. The method is characterized by the complete absence of ionizing radiation, portability and simplicity, fast acquisition, easy alignment of the 3D models, and wide angle of view of the scanner.

CONCLUSIONS

This method is completely noninvasive and can be repeated any time the physician needs new clinical records. The 3D virtual model is a precise representation both of the soft and the hard tissue scanned, and it is possible to make any dimensional measure directly in the virtual space, for a full integrated 3D anthropometry and cephalometry. Moreover, the authors propose a method completely based on close-range photogrammetric scanning, able to detect facial and dental surfaces, and reducing the time, the complexity, and the cost of the scanning operations and the numerical elaboration.

A 3D analysis of Caucasian and African American facial morphologies in a US population

INTRODUCTION

This study aimed to compare facial morphologies of an adult African-American population to an adult Caucasian-American population using three-dimensional (3D) surface imaging.

MATERIALS AND METHODS

The images were captured using a stereophotogrammetric system (3dMDface(TM) system). Subjects were aged 19-30 years, with normal body mass index and no gross craniofacial anomalies. Images were aligned and combined using RF6 Plus Pack 2 software to produce a male and female facial average for each population. The averages were superimposed and the differences were assessed.

RESULTS

The most distinct differences were in the forehead, alar base and perioricular regions. The average difference between African-American and Caucasian-American females was 1·18±0·98 mm. The African-American females had a broader face, wider alar base and more protrusive lips. The Caucasian-American females had a more prominent chin, malar region and lower forehead. The average difference between African-American and Caucasian-American males was 1·11±1·04 mm. The African-American males had a more prominent upper forehead and periocular region, wider alar base and more protrusive lips. No notable difference occurred between chin points of the two male populations.

CONCLUSIONS

Average faces were created from 3D photographs, and the facial morphological differences between populations and genders were compared. African-American males had a more prominent upper forehead and periocular region, wider alar base and more protrusive lips. Caucasian-American males showed a more prominent nasal tip and malar area. African-American females had broader face, wider alar base and more protrusive lips. Caucasian-American females showed a more prominent chin point, malar region and lower forehead.

Assessment of the accuracy of a three-dimensional imaging system for archiving dental study models

OBJECTIVE

The use of stone and plaster study models is an integral part of any dental practice and is required for research. Storage of study models is problematic in terms of space and cost. Ayoub et al.(1) introduced a new technique based on the recent advances in stereophotogrammetry for archiving dental study models in a digital format. However, assessment of the accuracy of the generated three-dimensional (3D) models has not been carried out yet. It was the aim of this study to evaluate the accuracy of this technique.

DESIGN

A comparative assessment between direct measurements of dental study models and measurements of computer generated 3D images of the same study models was performed.

MATERIALS AND METHODS

Twenty-two dental study models stored at Glasgow Dental Hospital and School for the purposes of research were used in the study. The models were captured in three dimensions using a photostereometric technique and stored in digital format.

MAIN OUTCOME MEASURES

Measurements were conducted directly on dental study models and on the computer generated 3D images using Euclidean Distance Matrix Analysis.(2) The difference between the two sets of measurements was statistically analysed using a two-sample t-test.

RESULTS

The average difference between measurements of dental casts and 3D images was 0.27 mm. This difference was within the range of operator errors (0.10-0.48 mm) and was not statistically significant (P < 0.05).

CONCLUSION

This study shows that it is possible to use 3D imaging to store dental study models for treatment monitoring and research with a satisfactory degree of accuracy.

Three-dimensional quantitative evaluation of facial morphology in adults with unilateral cleft lip and palate, and patients without clefts

The aims of this study were to assess the quantitative values of measurements using proportion indices in the craniofacial region in patients with repaired, non-syndromic, complete unilateral cleft lip and palate (UCLP), and compare them with a control group who did not have clefts using the non-invasive systems of 3-dimensional technology. Three-dimensional measurements of the facial surfaces of 15 Malay patients who had UCLP repaired and 100 Malay control patients aged 18-25 years were analysed. The 3-dimensional images of the respondents' faces were captured using the VECTRA-3D Stereophotogrammetry System. Eleven craniofacial proportions were assessed using a combination of 18 linear measurements obtained from 21 anthropometric soft tissue landmarks. These measurements were used to produce proportion indices to find the differences in the morphological features between the groups, and assessed using the independent sample t test and z scores. There were significant differences between the groups in 7 out of 11 craniofacial proportion indices (p=0.001-0.044). Z scores of 2 indices were disproportionate. They were nasal index (which was severely supernormal) and upper lip index (which was moderately supernormal). Patients with UCLP had higher mean z scores, indicating that patients with UCLP tended to have larger faces than the control group. There were clinically important differences mainly in the nasolabial area, where the nose and the upper lip were wider, larger, or flatter in patients with UCLP.

A comparison study of different facial soft tissue analysis methods

OBJECTIVES

The purpose of this study was to evaluate several different facial soft tissue measurement methods.

MATERIALS AND METHODS

After marking 15 landmarks in the facial area of 12 mannequin heads of different sizes and shapes, facial soft tissue measurements were performed by the following 5 methods: Direct anthropometry, Digitizer, 3D CT, 3D scanner, and DI3D system. With these measurement methods, 10 measurement values representing the facial width, height, and depth were determined twice with a one week interval by one examiner. These data were analyzed with the SPSS program.

RESULTS

The position created based on multi-dimensional scaling showed that direct anthropometry, 3D CT, digitizer, 3D scanner demonstrated relatively similar values, while the DI3D system showed slightly different values. All 5 methods demonstrated good accuracy and had a high coefficient of reliability (>0.92) and a low technical error (<0.9 mm). The measured value of the distance between the right and left medial canthus obtained by using the DI3D system was statistically significantly different from that obtained by using the digital caliper, digitizer and laser scanner (p < 0.05), but the other measured values were not significantly different. On evaluating the reproducibility of measurement methods, two measurement values (Ls-Li, G-Pg) obtained by using direct anthropometry, one measurement value (N'-Prn) obtained by using the digitizer, and four measurement values (EnRt-EnLt, AlaRt-AlaLt, ChRt-ChLt, Sn-Pg) obtained by using the DI3D system, were statistically significantly different. However, the mean measurement error in every measurement method was low (<0.7 mm). All measurement values obtained by using the 3D CT and 3D scanner did not show any statistically significant difference.

CONCLUSION

The results of this study show that all 3D facial soft tissue analysis methods demonstrate favorable accuracy and reproducibility, and hence they can be used in clinical practice and research studies.

Laser in dentistry: An innovative tool in modern dental practice

The term LASER is an acronym for ‘Light Amplification by the Stimulated Emission of Radiation’. As its first application in dentistry by Miaman, in 1960, the laser has seen various hard and soft tissue applications. In the last two decades, there has been an explosion of research studies in laser application. In hard tissue application, the laser is used for caries prevention, bleaching, restorative removal and curing, cavity preparation, dentinal hypersensitivity, growth modulation and for diagnostic purposes, whereas soft tissue application includes wound healing, removal of hyperplastic tissue to uncovering of impacted or partially erupted tooth, photodynamic therapy for malignancies, photostimulation of herpetic lesion. Use of the laser proved to be an effective tool to increase efficiency, specificity, ease, and cost and comfort of the dental treatment.

Assessment of facial asymmetry in growing subjects with a three-dimensional laser scanning system

OBJECTIVES

To evaluate facial asymmetry in growing subjects with no malocclusion on three-dimensional laser facial scans.

SETTING AND SAMPLE POPULATION

Twenty-seven healthy Caucasian children (15 boys and 12 girls, aged 5.4 ± 0.3 years) in the primary dentition without malocclusion were randomly selected from a local kindergarten in Slovenia.

MATERIAL AND METHODS

Surface facial images were obtained using a three-dimensional laser scanning system at baseline and at 18, 30, 42 and 54 months of follow-up. Facial asymmetry was assessed quantitatively by measuring the average distance between facial image and mirrored image. Further, the percentage of asymmetry was calculated as the percentage of image to mirrored image not coinciding within 0.5 mm. Qualitative assessment was performed on colour deviation maps by recording the predominant side of the face for the upper, middle and lower parts of the face separately. Nonparametric tests were used for data analysis.

RESULTS

No face was perfectly symmetric. The average distance between the mirrored images for the whole face ranged 0.22-0.85 mm and the percentage of asymmetry 7.8-66.9. There were no significant gender differences (p > 0.05), and no significant change was found over the observed period. The upper part of the face was the least asymmetric, while the lower and middle parts showed similar degrees of asymmetry.

CONCLUSION

Facial asymmetry is already present at an early developmental stage and does not show any tendency to increase or decrease with growth in the pre-pubertal period.

A new method for automatic tracking of facial landmarks in 3D motion captured images (4D)

The aim of this study was to validate the automatic tracking of facial landmarks in 3D image sequences. 32 subjects (16 males and 16 females) aged 18-35 years were recruited. 23 anthropometric landmarks were marked on the face of each subject with non-permanent ink using a 0.5mm pen. The subjects were asked to perform three facial animations (maximal smile, lip purse and cheek puff) from rest position. Each animation was captured by the 3D imaging system. A single operator manually digitised the landmarks on the 3D facial models and their locations were compared with those of the automatically tracked ones. To investigate the accuracy of manual digitisation, the operator re-digitised the same set of 3D images of 10 subjects (5 male and 5 female) at 1 month interval. The discrepancies in x, y and z coordinates between the 3D position of the manual digitised landmarks and that of the automatic tracked facial landmarks were within 0.17mm. The mean distance between the manually digitised and the automatically tracked landmarks using the tracking software was within 0.55 mm. The automatic tracking of facial landmarks demonstrated satisfactory accuracy which would facilitate the analysis of the dynamic motion during facial animations.

Accuracy and Repeatability of Anthropometric Facial Measurements Using Cone Beam Computed Tomography

Objective

The purpose of this study was to determine the accuracy and repeatability of linear anthropometric measurements on the soft tissue surface model generated from cone beam computed tomography scans.

Materials and Methods

The study sample consisted of seven cadaver heads. The accuracy and repeatability were assessed by means of a series of 21 standardized, linear facial measurements derived from 11 landmarks taken both directly on the face with a set of digital calipers and indirectly from a three-dimensional soft tissue surface model generated from a cone beam computed tomography scan of the heads using SimPlant® Ortho Pro software. The landmarks and measurements were chosen to cover various regions of the face with an emphasis on the oral-nasal region. The cone beam computed tomography measurements were compared with the physical measurements. Statistical analysis for the repeatability was done by means of the intraclass coefficient. Accuracy was determined by means of the absolute error and absolute percentage error.

Results

The cone beam computed tomography measurements were very accurate when compared with the physical measurements (0.962 to 0.999). Except for one measurement, between point tragion (t) and nasion (n) (mean, 1.52 mm), all the measurements had a mean absolute error of less than 1.5 mm.

Conclusions

The three-dimensional surface models derived from cone beam computed tomography images are sufficiently precise and accurate for the anthropometric measurements.

The effect of increased overjet on the magnitude and reproducibility of smiling in adult females

The objective of this study was to determine if increased overjet (greater than 6 mm) influences the magnitude and reproducibility of natural smile and maximal smile in Caucasian adult females. Twenty adult females with an increased overjet (6-10 mm) and 20 control adult females (overjet 2-4 mm) with no history of orthodontic treatment volunteered to participate. The mean age in the control group was 30.1 ± 6.4 years and the mean age in the test group was 31.9 ± 10.8 years. Three-dimensional stereophotogrammetric images were captured of each subject for three expressions: at rest, natural smile, and maximal smile. The images were recorded twice on two separate occasions, 6 weeks apart. Images were landmarked and a partial ordinary Procrustes superimposition was used to adjust for the differences in head posture between the same expressions. The magnitude of movement relative to the rest position, averaged over all the landmarks, was calculated and compared between the groups using analysis of variance (linear mixed-effects model); the intra- and inter-session reproducibility of both expressions was assessed. There was greater mean movement, averaged over all the landmarks, in the control group than in the increased overjet group for both natural smile and maximal smile (P = 0.0068). For these expressions, there were no statistically significant differences in reproducibility within sessions (P = 0.5403) or between sessions (P = 0.3665). Increased overjet had a statistically significant effect on the magnitude of smiling but did not influence the reproducibility of natural or maximal smile relative to controls.

Accurate facial morphologic measurements using a 3-camera photogrammetric method

OBJECTIVES

A new, low-cost photogrammetric method has been developed for facial morphometry applications. To evaluate the system, tests for the measurement and comparison of three-dimensional virtual faces were carried out in different subjects.

MATERIALS AND METHODS

Twenty adult white Italian subjects, 10 men and 10 women, of ages ranging from 23 to 37 years, were included in this study. Three cameras were finely calibrated, and the point precision vector length was calculated, together with the quality parameters. For each subject, 3 different acquisitions were performed. A tessellated surface was obtained from each point cloud. The comparison was made by aligning three-dimensional information from different models. Differences between 2 different models were estimated by analysis of the distances.

RESULTS

For the cases analyzed, the mean point precision overall root-mean-square vector length was 0.07 mm, with a SD of 0.027 mm. The results are reported for the system's capability of discriminating between the faces of different people. Results of comparisons between facial models of a single person were compared with those of comparisons between different subjects. Student's t-test revealed that the system was able to discriminate among different people, with a P > 95%. Two sex subgroups were formed: the mean error between subgroups ranged from 1.65 to 3.43 mm, and the mean ranged from 1.76 to 2.72 mm.

CONCLUSIONS

The experiments confirmed the capabilities and the accuracy of the proposed photogrammetric system. Facial comparison was performed by analysis of distances on three-dimensional virtual models.

Variation of the face in rest using 3D stereophotogrammetry

To evaluate treatment outcomes following oral and maxillofacial surgery, pre- and post-treatment three-dimensional (3D) photographs of the patient's face can assessed, but this procedure is accurate only if the face is captured with the same facial expression every time. The purpose of this prospective study was to determine variations in the face at rest; 100 3D photographs of the same individual were acquired at different times. Initially, 50 3D photographs were obtained; 25 using a wax bite to ensure similar occlusion between subsequent photographs and 25 without wax bite. This procedure was repeated 6 weeks later. Variation of the face at rest was computed. The influence of time and wax bite was investigated. Different anatomical regions were investigated separately. A mean variation of 0.25 mm (0.21-0.27 mm) was found (standard deviation 0.157 mm). No large differences were found between different time points or use of wax bite. Regarding separate anatomical regions, there were small variations in the nose and forehead regions; the largest variations were found in the mouth and eyes. This study showed small overall variation within the face at rest. In conclusion, different 3D photographs can be reproduced accurately and used in a clinical setting for treatment follow-up and evaluation.

Three-dimensional anthropometric analysis of chinese faces and its application in evaluating facial deformity

PURPOSE

The aims of this study are to introduce a novel method of 3-dimensional (3D) analysis of the face and to provide normative data of the Chinese face for surgeons.

MATERIALS AND METHODS

Fifty men and 50 women were recruited, and a 3D stereophotogrammetry system was used to acquire their facial image data. For each subject, the image was aligned to a unified coordinate system, and coordinate values of 31 facial landmarks were collected. Mean values for each landmark were calculated within genders, and 3D models of both genders were constructed based on the mean values. Subsequently, to evaluate the sexual dimorphism, the models were superimposed. Then, to delineate the shape differences independent of size, the models were normalized and superimposed again. The application of the 3D models was also exemplified by analysis of a subject's facial deformity.

RESULTS

Linear and polyhedron 3D models representing the facial shape were built for both genders. The superimposed models and the absolute differences between each landmark in both genders illustrated the sexual dimorphism of the Chinese face, and the normalized models and relative difference for each landmark also delineated the shape differences independent of size. In addition, a subject's facial deformity was evaluated by referring to the normative 3D facial models.

CONCLUSIONS

This study describes a new 3D analysis method for facial morphology. Three-dimensional models representing the facial shape of Chinese subjects were built, and sexual dimorphism was investigated. These would provide useful guidance for facial anthropometry and plastic surgeons in clinical practice.

3D assessment of lip scarring and residual dysmorphology following surgical repair of cleft lip and palate: a preliminary study

OBJECTIVE

To evaluate lip scarring and the three-dimensional (3D) lip morphology following primary reconstruction in children with unilateral cleft lip and palate (UCLP) relative to contemporaneous noncleft data.

DESIGN

Retrospective, cross-sectional, controlled study.

SETTING

Glasgow Dental Hospital and School, University of Glasgow, U.K.

PATIENTS AND PARTICIPANTS

Three groups of 10-year-old children: 51 with UCLP, 43 UCL (unilateral cleft lip), and 68 controls.

METHODS

Three-dimensional images of the face were recorded using stereo cameras on a two-pod capture station, and 3D coordinates of anthropometric landmarks were extracted from the facial images. A novel method was applied to quantify residual scarring and the associated lip dysmorphologies. The relationships among outcome measures were investigated.

RESULTS

Residual lip dysmorphologies were more pronounced in UCLP cases. The width of the Cupid's bow was increased due to lateral displacement of the christa philteri left (cphL) in both UCL and UCLP patients. In the upper part of the lip, the nostril base was significantly wider in UCLP cases when compared with UCL cases and controls. Scar redness was more pronounced in UCL than in UCLP cases. No relationship could be identified between lip scarring and other measurements of lip dysmorphology.

CONCLUSIONS

Stereophotogrammetry, together with associated image analysis, allow early detection of residual dysmorphology following cleft repair.

Registration of 3-dimensional facial photographs for clinical use

PURPOSE

To objectively evaluate treatment outcomes in oral and maxillofacial surgery, pre- and post-treatment 3-dimensional (3D) photographs of the patient's face can be registered. For clinical use, it is of great importance that this registration process is accurate (< 1 mm). The purpose of this study was to determine the accuracy of different registration procedures.

MATERIALS AND METHODS

Fifteen volunteers (7 males, 8 females; mean age, 23.6 years; range, 21 to 26 years) were invited to participate in this study. Three-dimensional photographs were captured at 3 different times: baseline (T(0)), after 1 minute (T(1)), and 3 weeks later (T(2)). Furthermore, a 3D photograph of the volunteer laughing (T(L)) was acquired to investigate the effect of facial expression. Two different registration methods were used to register the photographs acquired at all different times: surface-based registration and reference-based registration. Within the surface-based registration, 2 different software packages (Maxilim [Medicim NV, Mechelen, Belgium] and 3dMD Patient [3dMD LLC, Atlanta, GA]) were used to register the 3D photographs acquired at the various times. The surface-based registration process was repeated with the preprocessed photographs. Reference-based registration (Maxilim) was performed twice by 2 observers investigating the inter- and intraobserver error.

RESULTS

The mean registration errors are small for the 3D photographs at rest (0.39 mm for T(0)-T(1) and 0.52 mm for T(0)-T(2)). The mean registration error increased to 1.2 mm for the registration between the 3D photographs acquired at T(0) and T(L). The mean registration error for the reference-based method was 1.0 mm for T(0)-T(1), 1.1 mm for T(0)-T(2), and 1.5 mm for T(0) and T(L). The mean registration errors for the preprocessed photographs were even smaller (0.30 mm for T(0)-T(1), 0.42 mm for T(0)-T(2), and 1.2 mm for T(0) and T(L)). Furthermore, a strong correlation between the results of both software packages used for surface-based registration was found. The intra- and interobserver error for the reference-based registration method was found to be 1.2 and 1.0 mm, respectively.

CONCLUSION

Surface-based registration is an accurate method to compare 3D photographs of the same individual at different times. When performing the registration procedure with the preprocessed photographs, the registration error decreases. No significant difference could be found between both software packages that were used to perform surface-based registration.

Three-dimensional assessment of early surgical outcome in repaired unilateral cleft lip and palate: Part 1. Nasal changes

OBJECTIVE

To evaluate three-dimensional nasal morphology following primary reconstruction in children with unilateral cleft lip and palate relative to contemporaneous noncleft data.

DESIGN

Prospective, cross-sectional, controlled study.

SETTING

Glasgow Dental Hospital and School, Faculty of Medicine, Glasgow University.

PATIENTS AND PARTICIPANTS

Two groups of 3-year-old children (21 with unilateral cleft lip and palate and 96 controls) with facial images taken using a three-dimensional, vision-based capture technique.

METHODS

Three-dimensional images of the face were reflected so the cleft was on the left side to create a homogeneous group for statistical analysis. Three-dimensional coordinates of anthropometric landmarks were extracted from facial images by a single operator. A set of linear measurements was used to compare cleft and control subjects on right and left sides, adjusting for sex differences.

RESULTS

The mean nasal base width and the width of the nostril floor on right and left sides differed significantly between control and unilateral cleft lip and palate groups. The measurements were greater in children with unilateral cleft lip and palate. The differences in the mean nasal height and mean nasal projection between the groups were not statistically significant. Mean columellar lengths were different between the left and right sides in children with unilateral cleft lip and palate.

CONCLUSIONS

There were significant nasal deformities following the surgical repair of unilateral cleft lip and palate.

3D digital stereophotogrammetry: a practical guide to facial image acquisition

The use of 3D surface imaging technology is becoming increasingly common in craniofacial clinics and research centers. Due to fast capture speeds and ease of use, 3D digital stereophotogrammetry is quickly becoming the preferred facial surface imaging modality. These systems can serve as an unparalleled tool for craniofacial surgeons, proving an objective digital archive of the patient's face without exposure to radiation. Acquiring consistent high-quality 3D facial captures requires planning and knowledge of the limitations of these devices. Currently, there are few resources available to help new users of this technology with the challenges they will inevitably confront. To address this deficit, this report will highlight a number of common issues that can interfere with the 3D capture process and offer practical solutions to optimize image quality.

Intraobserver reliability of the 2-dimensional analysis of facial expressions

PURPOSE

The aim of our study was to develop a reliable method to identify certain facial expressions of the lower face that are easy to re-create through proper instruction and with high reproducibility. We wanted to quantitatively evaluate facial expressions in a simple, efficient, and inexpensive manner that is easily applicable in many clinical settings and in a wide variety of patients.

MATERIALS AND METHODS

We included 40 healthy subjects (20 women [mean age, 25.6 years] and 20 men [mean age, 27.0 years]). A digital camcorder recorded a video sequence (video 1) where the subject was verbally asked to execute several facial expressions (posed smile, spontaneous smile, aggressive smile, lip pucker, and maximum opening). Two weeks later, the video session was repeated (video 2). Frames of each expression were selected from the digitized video sequences. Horizontal and vertical distances were measured in each selected frame.

RESULTS

We found no statistically significant differences between the 2 videos of the expressions studied (except vertical lip changes for posed smile, lip pucker, and maximum mouth opening expression). The calculated coefficient of reliability was high and varied between 0.994 and 0.996, which confirms the reliability of the method.

CONCLUSION

This 2-dimensional method is an accurate means to quantitatively evaluate facial expressions in a simple, efficient, and inexpensive manner. The lip pucker, posed smile, spontaneous smile, and aggressive smile were the best and most reproducible expressions of the chosen expressions in this study.

Three-dimensional anthropometric analysis of the Chinese nose

Information about normal nasal dimensions is essential to rhinoplasty, but reports of anthropometric measurements of the Chinese nose are limited. Three-dimensional (3D) measuring apparatuses have been introduced into craniofacial anthropometry and have demonstrated advantages over conventional methods. This study aims to introduce a new 3D method for anthropometry and to provide guidance for plastic surgeons treating the Chinese nose. A total of 289 young Chinese adults (146 males and 143 females) were recruited for this study and a 3D stereo photogrammetry system (3DSS -II, Shanghai Digital Manufacturing Corporation, China) was used to acquire their facial image data. Geomagic Studio 10.0 software was used to process the data and to realign the images in a unified co-ordinate system. For each image, the co-ordinate values of 17 landmarks of the nose were collected, and the mean was calculated for males and females separately. Points based on the mean co-ordinate values were used to establish 3D stereo models. Subsequently, nasal parameters--including nine linear measurements, three angular measurements and seven proportions--were obtained by analysing these models. The 3D stereo models representing the Chinese male and female nasal shapes were built and the nasal parameters were acquired. Some differences between male and female nasal shapes were identified. This study describes a new method for 3D anthropometric analysis of the nose; the method would be applicable to anthropometry of other parts of the body as well. The 3D models of Chinese noses built in this study will provide very useful guidance for plastic surgeons in clinical practice.

Evolution of photography in maxillofacial surgery: from analog to 3D photography - an overview

In maxillofacial surgery, digital photographic documentation plays a crucial role in clinical routine. This paper gives an overview of the evolution from analog to digital in photography and highlights the integration of digital photography into daily medical routine. The digital workflow is described and we show that image quality is improved by systematic use of photographic equipment and post-processing of digital photographs. One of the advantages of digital photography is the possibility of immediate reappraisal of the photographs for alignment, brightness, positioning, and other photographic settings, which aids in avoiding errors and allows the instant repetition of photographs if necessary. Options for avoiding common mistakes in clinical photography are also described and recommendations made for post-processing of pictures, data storage, and data management systems. The new field of 3D digital photography is described in the context of cranial measurements.

Three-dimensional analysis of facial morphology surface changes in untreated children from 12 to 14 years of age

INTRODUCTION

The developing face is of interest to orthodontists, especially if orthodontic treatment can influence the outcome of facial growth. New 3-dimensional (3D) modalities have enabled clinicians to better understand the facial changes in a developing child.

METHODS

Fifty-nine children with normal body mass indexes were evaluated with a previously validated 3D laser imaging device over a 2-year period. Surface changes were evaluated on normal and average faces. These changes were seen as mean surface changes and color maps.

RESULTS

The results suggest that the surface areas of change in average faces were generally downward and forward with respect to the nose and soft-tissue nasion. The lips also translated in a downward direction as the nose grew, and there was a general increase in the vertical dimension. Some subjects were in the "great changes" category, boys significantly more so than girls.

CONCLUSIONS

The following conclusions can be made from this 3D study of changes of facial morphology in children: (1) surface changes are greater in boys than in girls; (2) differences in the timing of surface changes in boys and girls are clinically significant, with boys exhibiting more changes later; (3) positive surface changes occur in the nose, brows, lips, and vertical dimensions of the face; (4) the eyes deepen, and the cheeks become flatter; and (5) 3D imaging is a useful tool in analyzing changes to the face over time.

Validity and reliability of craniofacial anthropometric measurement of 3D digital photogrammetric images

BACKGROUND

Direct anthropometry performed during a patient examination is the standard technique for quantifying craniofacial dysmorphology, as well as for surgical planning and outcome assessment. Several new technologies have been designed to computerize anthropometric measurements, including three-dimensional (3D) digital photogrammetry. These digital systems have the advantage of acquiring patient craniofacial surface images quickly and noninvasively. Before morphometry using digital photogrammetry can be applied in clinical and research practice, it must be assessed against direct anthropometry.

OBJECTIVE

To evaluate the validity and reliability of facial anthropometric linear distances imaged by 3D digital photogrammetry with respect to direct anthropometry. DESIGN, SETTING, PARTICIPANTS, MEASURES: Standard craniofacial distances were directly measured twice on 20 normal adult volunteers. Craniofacial surfaces were also imaged using the 3dMDface digital photogrammetry system, and distances were digitally measured twice for each subject. Validity measures of accuracy and bias (for direct versus digital measurements) and reproducibility measures of precision and test-retest reliability (for repeated sets of digital measurements) were computed.

RESULTS

Seventeen of the 18 direct measurements correlated highly with digital values (mean r = 0.88). The correlation for one measurement (upper prolabial width) was not statistically significant. The overall precision of all 17 digital measurements was less than 1 mm, and the reliability was high (mean r = 0.91).

CONCLUSIONS

Craniofacial anthropometry using the 3dMDface System is valid and reliable. Digital measurements of upper prolabial width may require direct marking, prior to imaging, to improve landmark identification.

A three-dimensional look for facial differences between males and females in a British-Caucasian sample aged 151/2 years old

BACKGROUND

Optical surface scanning accurately records the three-dimension (3D) shape of the face non-invasively. Many software programs have been developed to process and analyze the 3D data, enabling the clinicians to create average templates for groups of subjects to provide a comparison of facial shape.

OBJECTIVE

Differences in facial morphology of males and females were identified using a laser scan imaging technology.

SUBJECTS AND METHODS

This study was undertaken on 380 British-Caucasian children aged 15 and a half year old, recruited from the Avon Longitudinal Study of Parents and Children (ALSPAC). 3D facial images were obtained for each individual using two high resolution Konica/Minolta laser scanners. The scan quality was assessed and any unsuitable scans were excluded from the study. Average facial templates were created for males and females, and a registration technique was used to superimpose the facial shells of males and females so that facial differences can be quantified.

RESULTS

Thirty unsuitable scans were excluded from the study. The final sample consisted of 350 subjects (166 females, 184 males). Females tend to have more prominent eyes and cheeks in relation to males with a maximum difference of 2.4 mm. Males tend to have more prominent noses and mouths with a maximum difference of 2.7 mm. About 31% of the facial shells match exactly (no difference), mainly in the forehead and chin regions of the face.

CONCLUSIONS

Differences in facial morphology can be accurately quantified and visualized using 3D imaging technology. This method of facial assessment can be recommended and applied for future research studies to assess facial soft tissue changes because of growth or healthcare intervention.

Validation and reproducibility of a high-resolution three-dimensional facial imaging system

OBJECTIVE

To assess the accuracy and reproducibility of a high-resolution three-dimensional imaging system (Di3D).

DESIGN

The three-dimensional imaging system was validated in vitro using 12 adult facial plaster casts, which had landmarks marked, and the positions of the landmarks on the three-dimensional images captured by Di3D were compared with those obtained by a coordinate measuring machine (CMM).

METHODS

Operator error was measured by repeatedly locating landmarks on the three-dimensional image. Reproducibility error of the images was calculated by capturing three-dimensional images of the facial casts on two separate occasions; the Euclidean distance between the two matched sets of coordinates was then calculated. The Di3D system error was assessed by calculating the three-dimensional global positions of landmarks on the three-dimensional images and comparing them with those obtained by CMM (gold standard).

RESULTS

The operator error in placement of landmarks on the three-dimensional model was 0.07mm, range 0.02-0.11mm. The reproducibility of the Di3D capture was 0.13mm, range 0.11-0.14mm. The mean distance between the CMM and Di3D landmarks, which constitutes the Di3D system error, was an average of 0.21mm, range 0.14-0.32mm.

CONCLUSIONS

The Di3D system error was within 0.2mm, which is clinically acceptable, and offers considerable improvement in stereophotogrammetry for facial capture and analysis.

The use of 3D face shape modelling in dysmorphology

Facial appearance can be a significant clue in the initial identification of genetic conditions, but their low incidence limits exposure during training and inhibits the development of skills in recognising the facial "gestalt" characteristic of many dysmorphic syndromes. Here we describe the potential of computer-based models of three-dimensional (3D) facial morphology to assist in dysmorphology training, in clinical diagnosis and in multidisciplinary studies of phenotype-genotype correlations.

Facial symmetry in unilateral cleft lip and palate following alar base augmentation with bone graft: a three-dimensional assessment

OBJECTIVE

The aim of this study was to assess the outcome of bone grafting using a corticocancellous block of iliac crest to reconstruct the support for the deformed, volume-deficient alar base in treated patients with unilateral cleft lip and palate (UCLP). The main outcome being measured was nasal symmetry.

DESIGN

This was a prospective study using a noninvasive three-dimensional stereophotogrammetry system (C3D) to assess the position of the alar base. Images were captured immediately preoperatively and at 6 months following the augmentation of the alar base with a block of bone graft. These images were used to calculate facial symmetry scores and were compared using a two sample Student's t test to assess the efficacy of the surgical method in reducing facial/nasal asymmetry.

PATIENTS

This investigation was conducted on 18 patients with one patient failing to attend for follow-up. The results for 17 patients are presented.

RESULTS

Facial symmetry scores improved significantly following the insertion of the bone graft at the deficient alar base (p=0.005).

CONCLUSIONS

3D stereophotogrammetry is a noninvasive, accurate, and archiveable method of assessing facial form and surgical change. Nasal symmetry can be quantified and measured reliably with this tool. Bone grafting to the alar base region of treated UCLP patients with volume deficiency produces improvement in nasal symmetry.

The validity of a computer-assisted simulation system for orthognathic surgery (CASSOS) for planning the surgical correction of class III skeletal deformities: single-jaw versus bimaxillary surgery

The aim of this study was to assess the accuracy of the two-dimensional profile prediction produced by the computer-assisted simulation system for orthognathic surgery (CASSOS), for the correction of class III facial deformities. Correction was by maxillary advancement (n=17) or bimaxillary surgery (n=16). The mean age was 24 years (range 18-42). The surgical and dental movements obtained from the postoperative cephalogram were used to produce a CASSOS profile prediction, which was compared with the soft-tissue profile. The prediction was superimposed onto the postoperative radiograph, and a coordinate system was used to measure linear differences. For the maxillary advancement group there were statistical differences for three horizontal landmarks: superior labial sulcus (p=0.017), labrale superious (p=0.038) and labiomental fold (p=0.014). In the bimaxillary group only the landmark vertical labrale superious (p=0.002) showed a statistical difference. Generally, CASSOS produced useful profile predictions for maxillary advancement surgery or bimaxillary surgery for Class III patients, although there was considerable individual variation. The main areas of inaccuracy were the lips. The major difference between the two types of surgery was that most of the errors in the maxillary surgery group were in the horizontal direction, whilst for the bimaxillary surgery the errors were mainly in the vertical direction.

Three-dimensional surface acquisition systems for the study of facial morphology and their application to maxillofacial surgery

BACKGROUND

There has been a growing interest in three-dimensional (3D) surface imaging devices over the last few years.

METHODS

This comprehensive review discusses the various emerging technologies in this field of 3D imaging and applies the use of technology to oral and maxillofacial imaging.

RESULTS

The paper shows that there is increased awareness and application of technology to the field.

CONCLUSION

3D surface acquisition technology is improving at a rapid pace and has a place in oral and maxillofacial surgery.

3D assessment of morbidity associated with lower eyelid incisions in orbital trauma

This study compared the morbidity associated with transconjunctival and transcutaneous approaches for orbital floor exploration with respect to the position of the lower eyelid following surgery. Two groups of 32 volunteers and 32 patients (12 transconjunctival and 20 transcutaneous) were recruited and three-dimensional (3D) imaging was carried out at 6 months following surgery. In the transcutaneous group, there were significant variations in the shape of the lower eyelid, with more medial displacement of the exocanthion. No significant differences were detected in the transconjunctival group compared to controls. The use of a 3D imaging system provided an objective method of assessing this aspect of morbidity associated with the use of lower eyelid incisions.

A Three-Dimensional Evaluation of Postoperative Swelling following Orthognathic Surgery at 6 Months

BACKGROUND

Advances in three-dimensional technology have enabled applications for the clinical setting to be created and used in routine diagnosis, treatment planning, and patient education. The objectives of this prospective clinical trial were to determine the volume changes associated with facial swelling following orthognathic surgery.

METHODS

Twelve subjects requiring orthognathic surgery were recruited for the study. Laser scanned images of the subjects were obtained under a reproducible, controlled environment with two laser-scanning devices assembled as a stereo pair. Three-dimensional laser scans were recorded over six time periods, as follows: T1, presurgical scan; T2, 1 day postoperatively; T3, 1 week postoperatively; T4, 1 month postoperatively; T5, 3 months postoperatively; and T6, 6 months postoperatively.

RESULTS

The results showed a clinical difference in the mean shell deviations between bimaxillary and single-jaw orthognathic surgery. Furthermore, the results suggest that the mean volume of swelling was reduced by approximately 60 percent within the first month after surgery. Finally, the amounts of swelling following surgery were greater in bimaxillary cases. The recovery in the swelling was also faster in this group of patients.

CONCLUSIONS

Three-dimensional imaging has opened up new avenues of patient care and treatment evaluation. The results have shown that the laser scanning device and the method described are a reliable and accurate measure of facial swelling following surgery.

Anthropometric precision and accuracy of digital three-dimensional photogrammetry: comparing the Genex and 3dMD imaging systems with one another and with direct anthropometry

A variety of commercially available three-dimensional (3D) surface imaging systems are currently in use by craniofacial specialists. Little is known, however, about how measurement data generated from alternative 3D systems compare, specifically in terms of accuracy and precision. The purpose of this study was to compare anthropometric measurements obtained by way of two different digital 3D photogrammetry systems (Genex and 3dMD) as well as direct anthropometry and to evaluate intraobserver precision across these three methods. On a sample of 18 mannequin heads, 12 linear distances were measured twice by each method. A two-factor repeated measures analysis of variance was used to test simultaneously for mean differences in precision across methods. Additional descriptive statistics (e.g., technical error of measurement [TEM]) were used to quantify measurement error magnitude. Statistically significant (P < 0.05) mean differences were observed across methods for nine anthropometric variables; however, the magnitude of these differences was consistently at the submillimeter level. No significant differences were noted for precision. Moreover, the magnitude of imprecision was determined to be very small, with TEM scores well under 1 mm, and intraclass correlation coefficients ranging from 0.98 to 1. Results indicate that overall mean differences across these three methods were small enough to be of little practical importance. In terms of intraobserver precision, all methods fared equally well. This study is the first attempt to simultaneously compare 3D surface imaging systems directly with one another and with traditional anthropometry. Results suggest that craniofacial surface data obtained by way of alternative 3D photogrammetric systems can be combined or compared statistically.

The 3-Dimensional Construction of the Average 11-Year-Old Child Face: A Clinical Evaluation and Application

PURPOSE

This article describes construction of the average face and its application in the clinical environment.

SUBJECTS AND METHODS

A total of 72 children, mean age 11.8 years, were selected for the study. Laser-scanned images of the subjects were obtained under a reproducible and controlled environment with 2 Minolta Vivid 900 (Minolta, Osaka, Japan) optical laser-scanning devices assembled as a stereo pair. A set of left and right scanned images was taken for each subject and each scan took an average of 2.5 seconds. These scanned images were processed and merged to form a composite 3-dimensional soft tissue reproduction of the subjects using commercially-available reverse modeling software. The differences in facial morphology were measured using shell deviation color maps. The average face was used to compare differences between male and female groups and 3 subjects with craniofacial anomalies.

RESULTS

The difference between the average male and female face was 0.460 +/- 0.353 mm. The areas of greatest deviation were at the zygomatic area and lower jaw line, with the males being more prominent. The results of the surface deviation between the subjects with craniofacial anomalies were significant.

CONCLUSIONS

The construction of the average face provides an interesting perspective into measuring changes in groups of patients and also acts as a useful template for the comparison of craniofacial anomalies.