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

The Accuracy of Three-Dimensional Soft Tissue Simulation in Orthognathic Surgery-A Systematic Review

Three-dimensional soft tissue simulation has become a popular tool in the process of virtual orthognathic surgery planning and patient-surgeon communication. To apply 3D soft tissue simulation software in routine clinical practice, both qualitative and quantitative validation of its accuracy are required. The objective of this study was to systematically review the literature on the accuracy of 3D soft tissue simulation in orthognathic surgery. The Web of Science, PubMed, Cochrane, and Embase databases were consulted for the literature search. The systematic review (SR) was conducted according to the PRISMA statement, and 40 articles fulfilled the inclusion and exclusion criteria. The Quadas-2 tool was used for the risk of bias assessment for selected studies. A mean error varying from 0.27 mm to 2.9 mm for 3D soft tissue simulations for the whole face was reported. In the studies evaluating 3D soft tissue simulation accuracy after a Le Fort I osteotomy only, the upper lip and paranasal regions were reported to have the largest error, while after an isolated bilateral sagittal split osteotomy, the largest error was reported for the lower lip and chin regions. In the studies evaluating simulation after bimaxillary osteotomy with or without genioplasty, the highest inaccuracy was reported at the level of the lips, predominantly the lower lip, chin, and, sometimes, the paranasal regions. Due to the variability in the study designs and analysis methods, a direct comparison was not possible. Therefore, based on the results of this SR, guidelines to systematize the workflow for evaluating the accuracy of 3D soft tissue simulations in orthognathic surgery in future studies are proposed.

Assessment of the reproducibility and accuracy of the Visia® Complexion Analysis Camera System for objective skin analysis of facial wrinkles and skin age

Objective

This study aimed to investigate the reproducibility and accuracy of the Visia® Complexion Analysis Camera System by Canfield Scientific for objective skin analysis.

Methods

Nineteen participants underwent facial capture with the Visia® camera following a standardised protocol. During the first session, the participants sat down and positioned their faces in a capture rig, closed their eyes and had their faces captured from the left, front and right sides, with threefold repetition of the captures from the front side. After 4 weeks, the participants underwent recapture in a similar manner. Based on the frontal views, data for two measurement methods of the Visia® camera system, the absolute scores and the percentiles, were obtained with regard to the skin criterion wrinkles via automated software calculation. Means and standard deviations were evaluated. Based on the side views, the data for the Truskin Ages® were calculated by the Visia® camera system and compared with the calendrical ages, which served as the gold standard for comparison.

Results

In the assessment of the reproducibility of the data of the capture system the standard deviation from the frontal captures among all participants was about 3% when the absolute scores of the wrinkles were compared with each other; specifically, the average deviation was 3.36% during the first capture session and 3.4% during the second capture session. Meanwhile, the standard deviation of the measurements was about 9% when the percentiles were compared; specifically, the average deviation was 8.2% during the first capture session and 10.7% during the second capture session. In the assessment of the accuracy the correlation between the calendrical age and the calculated Truskin Age® for both facial sides was very high at a correlation coefficient rho value of >0.8 (right side: r=0.896; left side: r=0.827) and statistically significant at a p-value of <0.001. The average calendrical age and Truskin Age® deviated only slightly from each other and did not differ significantly (right side: p=0.174; left side: p=0.190). The Truskin Age® was slightly higher than the calendrical age by a mean value of 1.37 years for both facial sides. The analysis of the absolute differences revealed that in 50% of the cases, there was a maximum difference of 3 years, and in 75% of the cases, there were maximum differences of 4.5 years for the right side and 5.5 years for the left side.

Conclusion

The assessment of the reproducibility and accuracy of the objective measurement method, the Visia® camera system, contributed to the validation of the system. The evaluation of the reproducibility revealed a satisfactory precision of the repeated captures when investigating facial wrinkles. Absolute scores should be preferred over percentiles owing to their better precision. The calculation of the accuracy of the Truskin Age® data from the Visia® camera system revealed only a slight deviation from the true calendrical ages. The correlation between both data groups was highly significant.

An innovative analysis of nasolabial dynamics of surgically managed adult patients with unilateral cleft lip and palate using 3D facial motion capture

AIM

To compare dynamic nasolabial movement between end-of-treatment cleft and a matched non-cleft group in adult patients.

MATERIALS AND METHODS

Thirteen treated adult participants with unilateral cleft lip and palate had images taken using a facial motion capture system performing a maximum smile. Seventeen landmarks were automatically tracked. For each landmark pair, on either side of the midline, changes in the x, y, and z directions were used to analyze the magnitude of displacement and path of motion. An asymmetry score was developed at rest, mid-smile, and maximum smile to assess the shape of the mouth and/or nose.

RESULTS

At maximum smile, displacement of right and left cheilion was clinically and statistically (p < 0.05) less in the cleft group. The lip asymmetry score was greater (p < 0.05) at each time point in the cleft group using the clinical midline. Using Procrustes superimposition, the differences were significant (p < 0.05) only at rest and mid-smile. The alar bases were displaced significantly less (p < 0.05) in the z direction in the cleft group. The asymmetry score of the alar base was significantly higher using the clinical midline than using Procrustes superimposition in patients with cleft conditions (p < 0.001). In the cleft group, at maximum smile, the right and left cristae philter moved significantly less (p < 0.05) in the x and z directions.

CONCLUSIONS

There was an increase in asymmetry score of the corners of the mouth and alar bases from rest to maximum smile. The lips were similar in shape but oriented differently in the faces of patients with cleft conditions than in individuals without those conditions.

Comparison of Manual (2D) and Digital (3D) Methods in the Assessment of Simulated Facial Edema

BACKGROUND

An edema assessment following dental surgeries is essential to improving the dental surgeon's technique and, consequentially, patient comfort.

PURPOSE

Two-dimensional (2D) methods are limited in analyzing 3-dimensional (3D) surfaces. Currently, 3D methods are used to investigate postoperative swelling. However, there are no studies that directly compare 2D and 3D methods. The goal of this study is to directly compare 2D and 3D methods used in the assessment of postoperative edema.

STUDY DESIGN AND SAMPLE

The investigators implemented a prospective, cross-sectional study with each subject serving as its own control. The sample was composed of dental student volunteers without facial deformities.

PREDICTOR VARIABLE

The predictor variable is the method used to measure edema. After simulating edema, manual (2D) and digital (3D) techniques were used to measure edema. The manual method used direct facial perimeter measurements. The two digital methods were photogrammetry using a smartphone (iPhone 11, Apple Inc, Cupertino, California), and facial scanning with a smartphone application (Bellus3D FaceApp, Bellus3D Inc, Campbell, California) [3D measurements] MAIN OUTCOME VARIABLE: The coefficient of variation (CV) (CV = standard deviation /mean) was used to assess homogeneity of edema measurements.

ANALYSIS

The Shapiro-Wilk and equal variance tests were applied to assess data homogeneity. Next, one-way analysis of variance was performed, followed by a correlation analysis. Finally, the data were submitted to Tukey's test. The statistical significance threshold was set at 5% (P < .05).

RESULTS

The sample was composed of 20 subjects aged 18-38 years. The CV showed higher values using the manual (2D) method (47%; 4.88% ± 2.99), compared with the photogrammetry method (18%; 8.55 mm ± 1.52) and the smartphone application (21%; 8.97 mm ± 1.93). A statistically significant difference was observed between the manual method values and those of the other two groups (P < .001). There was no difference between the facial scanning and photogrammetry groups (3D methods) (P = .778) CONCLUSION AND RELEVANCE: Both digital measuring methods (3D) demonstrated greater homogeneity than the manual method in analyzing facial distortions caused by the same swelling simulation. Therefore, it can be affirmed that digital methods may be more reliable that manual methods for assessing facial edema.

Slim the face or not: 3D change of facial soft and hard tissues after third molars extraction: a pilot study

BACKGROUND

Whether slim the face or not after removed third molars is the concern of some orthodontic treatment candidates. The aim of this article is to explore the volume changes of facial soft and hard tissues after third molars extraction, as well as develop a reproducible clinical protocol to precisely assess facial soft tissue volume change.

METHODS

A non-randomized, non-blind, self-controlled pilot study was conducted. 24 adults aged 18-30 had ipsilateral third molars extracted. The body weight change was controlled within 2 kg. Structured light scans were taken under a standardized procedure pre-extraction (T0), three (T1), and six (T2) months post-extraction; CBCTs were taken at T0 and T2. The projection method was proposed to measure the soft tissue volume (STV) and the soft tissue volume change (STVC) by the Geomagic software. The hard tissue volume change (HTVC) was measured in the Dragonfly software.

RESULTS

The final sample size is 23, including 5 males (age 26.6 ± 2.5 years) and 18 females (age 27.3 ± 2.5 years). The HTVC was - 2.33 ± 0.46ml on the extraction side. On the extraction side, the STV decreased by 1.396 (95% CI: 0.323-2.470) ml (P < 0.05) at T1, and increased by 1.753 (95% CI: -0.01-3.507) ml (P = 0.05) at T2. T2 and T0 had no difference (P > 0.05). The inter and intra-raters ICC of the projection method was 0.959 and 0.974. There was no correlation between the STVC and HTVC (P > 0.05).

CONCLUSIONS

After ipsilateral wisdom teeth extraction, the volume of hard tissue on the extraction side reduces, and the volume of facial soft tissue does not change evidently. However, further research with large sample size is still needed. The STV measurement has excellent repeatability. It can be extended to other interested areas, including forehead, nose, paranasal, upper lip, lower lip and chin, which is meaningful in the field of orthodontics and orthopedics.

TRIAL REGISTRATION

ChiCTR, ChiCTR1800018305 (11/09/2018), http://www.chictr.org.cn/showproj.aspx?proj=28868 .

Validity and reliability of three-dimensional modeling of orthodontic dental casts using smartphone-based photogrammetric technology

BACKGROUND

The development of intraoral scanning technology has effectively enhanced the digital documentation of orthodontic dental casts. Albeit, the expense of this technology is the main limitation. The purpose of the present study was to assess the validity and reliability of virtual three-dimensional (3D) models of orthodontic dental casts, which were constructed using smartphone-based 3D photogrammetry.

METHODS

A smartphone was used to capture a set of two-dimensional images for 30 orthodontic dental casts. The captured images were processed to construct 3D virtual images using Agisoft and 3DF Zephyr software programs. To evaluate the accuracy of the virtual 3D models obtained by the two software programs, the virtual 3D models were compared with cone-beam computed tomography scans of the 30 dental casts. Colored maps were used to express the absolute distances between the points of each compared two surfaces; then, the means of the 100%, 95th, and 90th of the absolute distances were calculated. A Wilcoxon signed-rank test was applied to detect any significant differences.

RESULTS

The differences between the constructed 3D images and the cone-beam computed tomography scans were not statistically significant and were accepted clinically. The deviations were mostly in the interproximal areas and in the occlusal details (sharp cusps and deep pits and fissures).

CONCLUSIONS

This study found that smartphone-based stereophotogrammetry is an accurate and reliable method for 3D modeling of orthodontic dental casts, with errors less than the accepted clinically detectable error of 0.5 mm. Smartphone photogrammetry succeeded in presenting occlusal details, but it was difficult to accurately reproduce interproximal areas.

Anthropometric accuracy of three-dimensional average faces compared to conventional facial measurements

This study aimed to evaluate and compare the accuracy of average faces constructed by different methods. Original three-dimensional facial images of 26 adults in Chinese ethnicity were imported into Di3DView and MorphAnalyser for image processing. Six average faces (Ave_D15, Ave_D24, Ave_MG15, Ave_MG24, Ave_MO15, Ave_MO24) were constructed using "surface-based registration" method with different number of landmarks and template meshes. Topographic analysis was performed, and the accuracy of six average faces was assessed by linear and angular parameters in correspondence with arithmetic means calculated from individual original images. Among the six average faces constructed by the two systems, Ave_MG15 had the highest accuracy in comparison with the conventional method, while Ave_D15 had the least accuracy. Other average faces were comparable regarding the number of discrepant parameters with clinical significance. However, marginal and non-registered areas were the most inaccurate regions using Di3DView. For MorphAnalyser, the type of template mesh had an effect on the accuracy of the final 3D average face, but additional landmarks did not improve the accuracy. This study highlights the importance of validating software packages and determining the degree of accuracy, as well as the variables which may affect the result.

Accuracy between virtual surgical planning and actual outcomes in orthognathic surgery by iterative closest point algorithm and color maps: A retrospective cohort study

BACKGROUND

To evaluate the accuracy between actual outcomes and virtual surgical planning (VSP) in orthognathic surgery regarding the use of three-dimensional (3D) surface models for registration using iterative closest point (ICP) algorithm and generated color maps.

MATERIAL AND METHODS

Construction of planning and postoperative 3D models in STL files format (M0 and M1, respectively) from CBCT of 25 subjects who had been submitted to bimaxillary orthognathic surgery was performed. M0 and M1 were sent to Geomagic software in semi-automatic alignment surface mesh order of M0 and M1 for registration using ICP algorithm to calculate mean deviation (MD, MD+, MD-, SD) and root mean square (RMS - 3D Error). Color maps were generated to assess qualitative congruence between M0 and M1. From deviation analysis, 3D Error was defined as accuracy measurement. To assess the reproducibility, the workflow was performed by two evaluators multiple times. t-tests were used to assess whether all means of MD, MD+, MD-, SD and 3D Error values would be ≤ - 2 mm and ≥ 2 mm.

RESULTS

High intra and inter evaluators correlation were found, supporting the reproducibility of the workflow. t-tests proved that all MDs and 3D Error values were > - 2 mm and < 2 mm.

CONCLUSIONS

3D error mean was within the standards of clinical success lower than 2 mm. ICP algorithm provided a reproducible method of alignment between 3D models and generated color maps to evaluate 3D congruence but did not answer all methodological parameters regarding the assessment of accuracy in orthognathic surgery.

The effect of facial expression on facial symmetry in surgically managed unilateral cleft lip and palate patients (UCLP)

AIM

To evaluate the symmetry of facial expression in surgically managed UCLP patients.

MATERIALS AND METHODS

The study was conducted on 13 four-year-old children. Facial images were captured at rest and at maximum smile using stereophotogrammetry. A generic mesh, which is a mathematical facial mask consisting of a fixed number of indexed vertices, was utilised for the assessment of facial asymmetry. This was quantified by measuring the disparity between the left- and right-hand sides of the face after superimposing the original 3D images on their mirror copies.

RESULTS

Residual asymmetries at rest were identified at the vermillion of the upper lip and at the nares with a deviation of the philtrum towards the scar tissue. Vertical and anteroposterior asymmetries were identified on the cleft side. At maximum smile, the asymmetry increased noticeably at the vermillion of the upper lip and at the alar base. In the mediolateral direction, the philtrum deviated towards the cleft side with a significant increase of the asymmetry scores.

DISCUSSION

Asymmetry of the upper lip has significantly increased at maximum smile as a result of the upward forces of all perioral lifting muscles, which affected the lip directly.

CONCLUSIONS

The innovation of this study is the measurement of facial asymmetry for the objective outcome measure of the surgical repair of UCLP. The philtrum was the main site of residual asymmetry, which indicates the need for refining the primary repair of the cleft lip. Further corrective surgery may be required.

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.

Using three-dimensional average facial meshes to determine nasolabial soft tissue deformity in adult UCLP patients

BACKGROUND AND PURPOSE

There is limited literature discussing the residual nasolabial deformity of adult patients prior to undergoing orthognathic surgery. The purpose of this study is to determine the site and severity of the residual nasolabial soft tissue deformity between adult unilateral cleft lip and palate (UCLP) patients and a non-cleft reference group, prior to orthognathic surgery.

MATERIAL AND METHODS

Sixteen adult male UCLP patients, who all received primary lip and palate surgery according to a standardised Hong Kong protocol were recruited for this study. Facial images of each individual were captured using three-dimensional (3D) stereophotogrammetry and compared to a previous published Hong Kong non-cleft reference group of 48 male adults. Using two-sample t-tests differences in linear and angular measurements and asymmetry scores were evaluated between the two groups. In addition a "conformed" average UCLP facial template was superimposed and compared to conformed average non-cleft reference group facial template. Reproducibility of the measurements were assessed using Students paired t-tests and coefficients of reliability.

MAIN FINDINGS

Significant differences in linear and angular measurements and asymmetry scores were observed between the two groups (p < 0.05). Adult UCLP patients showed significantly narrower nostril floor widths, longer columella length on the unaffected side, a wider nose, shorter cutaneous lip height, shorter upper lip length and shorter philtrum length. Prior to orthognathic surgery adult UCLP patients showed significantly more facial asymmetry. Superimposition of the average facial meshes clearly showed the site and severity of the deficiency in the x, y and z-directions.

CONCLUSIONS

Many of the nasolabial characteristics reported to be present in children following primary UCLP repair continue into adulthood. The detrimental soft tissue effects of orthognathic surgery for UCLP patients may be different to non-cleft individuals; and as such the site and severity of the residual deformity should be assessed prior to surgery.

An in-vitro study to assess the feasibility, validity and precision of capturing oncology facial defects with multimodal image fusion

AIM

Assess the feasibility, validity and precision of multimodal image fusion to capture oncology facial defects based on plaster casts.

METHODS

Ten casts of oncology facial defects were acquired. To create gold standard models, a 3D volumetric scan of each cast was obtained with a cone beam computed tomography (CBCT) scanner (NewTomVG). This was converted into surface data using open-source medical segmentation software and cropped to produce a CBCT mask using an open-source system for editing meshes. For the experimental model, the external facial features were captured using stereophotogrammetry (DI4D) and the defect was recorded with a custom optical structured light scanner. The two meshes were aligned, merged and resurfaced using MeshLab to produce a fused model. Analysis was performed in MeshLab on the best fit of the fused model to the CBCT mask. The unsigned mean distance was used to measure the absolute deviation of each model from the CBCT mask. To assess the precision of the technique, the process of producing the fused model was repeated to create five models each for the casts representing the best, middle and worst results.

RESULTS

Global mean deviation was 0.22 mm (standard deviation 0.05 mm). The precision of the method appeared to be acceptable although there was variability in the location of the error for the worst cast.

CONCLUSION

This method for merging two independent scans to produce a fused model shows strong potential as an accurate and repeatable method of capturing facial defects. Further research is required to explore its clinical use.

The accuracy of three-dimensional prediction of soft tissue changes following the surgical correction of facial asymmetry: An innovative concept

The accuracy of three-dimensional (3D) predictions of soft tissue changes in the surgical correction of facial asymmetry was evaluated in this study. Preoperative (T1) and 6-12-month postoperative (T2) cone beam computed tomography scans of 13 patients were studied. All patients underwent surgical correction of facial asymmetry as part of a multidisciplinary treatment protocol. The magnitude of the surgical movement was measured; virtual surgery was performed on the preoperative scans using Maxilim software. The predicted soft tissue changes were compared to the actual postoperative appearance (T2). Mean (signed) distances and mean (absolute) distances between the predicted and actual 3D surface meshes for each region were calculated. The one-sample t-test was applied to test the alternative hypothesis that the mean absolute distances had a value of <2.0mm. A novel directional analysis was applied to analyse the accuracy of the prediction of soft tissue changes. The results showed that the distances between the predicted and actual postoperative soft tissue changes were less than 2.0mm in all regions. The predicted facial morphology was narrower than the actual surgical changes in the cheek regions. 3D soft tissue prediction using Maxilim software in patients undergoing the correction of facial asymmetry is clinically acceptable.