Establishment of the mid-sagittal reference plane for three-dimensional assessment of facial asymmetry: a systematic review : Establishment of the mid-sagittal reference plane: a systematic review.

OBJECTIVE: To systematically review the literature for mid-sagittal plane establishment approaches to identify the most effective method for constructing the mid-sagittal plane for the evaluation of facial asymmetry. MATERIALS AND METHODS: Six electronic databases (PubMed, Medline (via Ovid), EMBASE (via Ovid), Cochrane Library, Web of Science, and Scopus) and grey literature were searched for the studies that computed the mid-sagittal reference plane three-dimensionally, using a combination of MeSH terms and keywords. The methodological quality and the level of evidence for the included studies were analyzed using QUADAS-2 and GRADE, respectively. RESULTS: The preliminary search yielded 6746 records, of which 42 articles that met the predefined inclusion criteria were included in the final analysis. All the included articles reported the construction of the mid-sagittal reference plane (MSP) using varied methods. The risk of bias and concerns regarding the applicability of the included studies were judged to be 'low'. The level of evidence was determined to be 'low' for the effectiveness of the technique and 'moderate' for the ease of clinical applicability. CONCLUSION: Despite methodological heterogeneity, this review substantiates the comparable efficacy of cephalometric and morphometric MSP construction methods. A fully automated morphometric MSP holds promise as a viable option for routine clinical use. Nevertheless, future prospective studies with an emphasis on the impact, accuracy, and clinical applicability of MSP construction techniques in cases of facial asymmetry are required. CLINICAL RELEVANCE: The present review will assist clinicians in selecting the most suitable method for MSP construction, leading to improved treatment planning and ultimately more favorable treatment outcomes.

The validity of using profile predictions for class III patients planned for bimaxillary orthognathic surgery.

This study assessed whether preoperative class III patients could recreate their facial difference based on a profile photograph. Twenty class III pre-surgery bimaxillary orthognathic patients used CASSOS (SoftEnable Technology Ltd.) to manipulate a distorted soft tissue image of them until they felt it resembled their current soft tissue profile. Patients were able to move their upper lip and lower chin backward and forwards, as well as the lower chin up and down. Differences in the mean absolute distance between the patient-perceived position of the upper lip (Labrale superious) and chin (Pogonion) and the actual position of their upper lip and chin were measured on two occasions. Intra-patient reproducibility was found to be excellent (ICC 0.93 to 0.98). All differences were statistically significantly greater than 3mm, and would be clinically significant. Patients were better at re-creating their AP chin position rather than their AP upper lip and vertical chin positions. Approximately half of patients undergoing surgical correction of their class III skeletal pattern were unable to correctly identify their pre-surgical facial profile. Given the lack of awareness of their profile, this questions the validity of using profile planning for informed consent.

Three-dimensional assessment of facial asymmetry in Class III subjects. Part 1: a retrospective study evaluating postsurgical outcomes.

OBJECTIVE: The present study aimed to determine the site and severity of maxillomandibular asymmetry before and after orthognathic surgery in asymmetric patients. MATERIALS AND METHODS: Presurgery and postsurgery cone beam computed tomography (CBCT) data of 21 facial asymmetry patients (7 males and 14 females, mean age: 23.0 ± 3.36 years) with soft tissue chin deviation ≥ 3 mm who had undergone bimaxillary surgery were evaluated. Seven midline and twenty bilateral hard tissue landmarks were identified for the evaluation of facial asymmetry and outcomes were assessed against age- and gender-matched control subjects. RESULTS: In the asymmetry group, bilateral landmarks exhibited significant deviation in the mandible and midface regions. Before surgery, asymmetry was more severe at the mandibular midline and sites close to it, in the asymmetry group. Bimaxillary surgery proved to be highly effective, with a significant correction of the menton to a clinically normal value (2.90 mm, p < 0.001). After surgery, significant residual asymmetry was observed at the mental foramen (p = 0.001) in the R-L direction. Moreover, significant asymmetry persisted at the sigmoid notch (p = 0.001) in the S-I direction. CONCLUSIONS: Mandibular midline landmarks and chin peripheral regions contribute significantly to overall facial asymmetry characteristics. Despite significant correction after bimaxillary surgery, asymmetry persisted at several sites, thereby requiring secondary correction. Comprehensive 3D presurgical planning is central for asymmetry correction in a single surgery. CLINICAL RELEVANCE: The present study specifies the location of residual asymmetry sites and advocates the correction of those sites during initial surgery.

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.

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.

Accuracy of capturing oncology facial defects with multimodal image fusion versus laser scanning.

STATEMENT OF PROBLEM: Fabrication of conventional facial prostheses is a labor-intensive process which traditionally requires an impression of the facial defect and surrounding tissues. Inaccuracies occur during the facial moulage because of soft-tissue compression, the patient's reflex movements, or the lack of support for the impression material. A variety of 3D imaging techniques have been introduced during the production of facial prostheses. However, the accuracy of the different imaging techniques has not been evaluated sufficiently in this clinical context. PURPOSE: The purpose of this in vitro study was to compare the difference in accuracy of capturing oncology facial defects with multimodal image fusion and laser scanning against a cone beam computed tomography (CBCT) reference scan. MATERIAL AND METHODS: Ten gypsum casts of oncology facial defects were acquired. To produce reference models, a 3D volumetric scan was obtained using a CBCT scanner and converted into surface data using open-source medical segmentation software. This model was cropped to produce a CBCT mask using an open-source system for editing meshes. The multimodal image fusion model was created using stereophotogrammetry to capture the external facial features and a custom optical structured light scanner to record the defect. The gypsum casts were also scanned using a commercial 3D laser scanner to create the laser-scanned model. Analysis of the best fit of each experimental model to the CBCT mask was performed in MeshLab. The unsigned mean distance was used to measure the absolute deviation of each model from the CBCT mask. A paired-samples t test was conducted to compare the mean global deviation of the 2 imaging modalities from the CBCT masks (α=.05). RESULTS: A statistically significant difference was found in the mean global deviation between the multimodal imaging model (220 ±50 µm) and the laser-scanned model (170 ±70 µm); (t(9)=2.56, P=.031). The color error maps illustrated that the greatest error was located at sites distant to the prosthesis margins. CONCLUSIONS: The laser-scanned models were more accurate; however, the mean difference of 50 µm is unlikely to be clinically significant. The laser scanner had limited viewing angles and a longer scan time which may limit its transferability to maxillofacial practice.

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.

Dental Arch Relationships and Reverse Headgear Effects in Southern Chinese Patients with Unilateral Cleft Lip and Palate: A Retrospective Study.

OBJECTIVE: To evaluate the severity of the dental arch relationships and the treatment outcomes of reverse headgear (RHG) in southern Chinese patients with unilateral cleft lip and palate (UCLP). DESIGN: A retrospective study. SETTING: Faculty of Dentistry, The University of Hong Kong. PATIENTS: Thirty-eight UCLP patients with complete records. Among them, 14 were later treated with RHG (RHG group) and 24 were under review (non-RHG group) before definitive orthodontic or in conjunction with orthognathic surgery. INTERVENTIONS: Study models at T1 (aged 9.4 ± 0.4 years old), prebone grafting and before any orthodontic treatment started; T2 (aged 11.3 ± 0.6 years old), after bone grafting, and RHG treatment (RHG group) or under review (non-RHG group); and T3 (aged 15.3 ± 3.2 years old), pretreatment of definitive orthodontic or in conjunction with orthognathic surgery. MAIN OUTCOME MEASURES: With satisfactory intra- and interexaminer agreement proven by the kappa value, the dental arch relationships of the study models at T1, T2, and T3 were assessed by a solo calibrated examiner using the GOSLON Yardstick. RESULTS: The median GOSLON score for southern Chinese patients with UCLP at T1 was 4.0. Sixty percent of the patients were categorized as "poor" at T1. RHG significantly improved dental arch relationships from T1 to T2, and the improvement was maintained until T3 assessed by the GOSLON Yardstick. CONCLUSIONS: The dental arch relationships in southern Chinese UCLP patients at 8 to 10 years old are unfavorable. RHG treatment shows positive effects in improving the dental arch relationships in UCLP patients, as assessed by the GOSLON Yardstick.

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.

Haptic simulation framework for determining virtual dental occlusion.

PURPOSE: The surgical treatment of many dentofacial deformities is often complex due to its three-dimensional nature. To determine the dental occlusion in the most stable position is essential for the success of the treatment. Computer-aided virtual planning on individualized patient-specific 3D model can help formulate the surgical plan and predict the surgical change. However, in current computer-aided planning systems, it is not possible to determine the dental occlusion of the digital models in the intuitive way during virtual surgical planning because of absence of haptic feedback. In this paper, a physically based haptic simulation framework is proposed, which can provide surgeons with the intuitive haptic feedback to determine the dental occlusion of the digital models in their most stable position. METHODS: To provide the physically realistic force feedback when the dental models contact each other during the searching process, the contact model is proposed to describe the dynamic and collision properties of the dental models during the alignment. The simulated impulse/contact-based forces are integrated into the unified simulation framework. RESULTS: A validation study has been conducted on fifteen sets of virtual dental models chosen at random and covering a wide range of the dental relationships found clinically. The dental occlusions obtained by an expert were employed as a benchmark to compare the virtual occlusion results. The mean translational and angular deviations of the virtual occlusion results from the benchmark were small. CONCLUSIONS: The experimental results show the validity of our method. The simulated forces can provide valuable insights to determine the virtual dental occlusion. The findings of this work and the validation of proposed concept lead the way for full virtual surgical planning on patient-specific virtual models allowing fully customized treatment plans for the surgical correction of dentofacial deformities.

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.

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.

"Direct DICOM Slice Landmarking" A Novel Research Technique to Quantify Skeletal Changes in Orthognathic Surgery.

The limitations of the current methods of quantifying the surgical movements of facial bones inspired this study. The aim of this study was the assessment of the accuracy and reproducibility of directly landmarking of 3D DICOM images (Digital Imaging and Communications in Medicine) to quantify the changes in the jaw bones following surgery. The study was carried out on plastic skull to simulate the surgical movements of the jaw bones. Cone beam CT scans were taken at 3mm, 6mm, and 9mm maxillary advancement; together with a 2mm, 4mm, 6mm and 8mm "down graft" which in total generated 12 different positions of the maxilla for the analysis. The movements of the maxilla were calculated using two methods, the standard approach where distances between surface landmarks on the jaw bones were measured and the novel approach where measurements were taken directly from the internal structures of the corresponding 3D DICOME slices. A one sample t-test showed that there was no statistically significant difference between the two methods of measurements for the y and z directions, however, the x direction showed a significant difference. The mean difference between the two absolute measurements were 0.34±0.20mm, 0.22±0.16mm, 0.18±0.13mm in the y, z and x directions respectively. In conclusion, the direct landmarking of 3D DICOM image slices is a reliable, reproducible and informative method for assessment of the 3D skeletal changes. The method has a clear clinical application which includes the analysis of the jaw movements "orthognathic surgery" for the correction of facial deformities.

Reducing cone beam CT scan height as a method of radiation reduction for photorealistic three-dimensional orthognathic planning.

OBJECTIVES: To determine the superimposition accuracy of full-face stereophotographic images with 22 cm and 13 cm cone beam computed tomography (CBCT) scans. MATERIAL AND METHODS: 22 cm CBCT scans and corresponding stereophotographic images (3 dMD) for 30 subjects requiring orthognathic surgery were randomly selected. A 13 cm CBCT scan was generated from the 22 cm scan for each subject. All scans and images were converted into STL format. For each subject, the 22 cm and 13 cm CBCT scans were imported into CAD/CAM software and each superimposed with the corresponding 3 dMD image. A one-sample t-test was used to test the null hypothesis that the difference in the 90th percentile of the mean absolute distance between the two 3dMD images when aligned on the 22 cm and the 13 cm CBCT scans was not clinically significant (<0.5 mm). RESULTS: The 90th percentile of the mean absolute distance between the two 3 dMD surfaces using the 22 cm and 13 cm CBCT scans was significantly less than 0.5 mm (p < 0.001; 0.2 ± 0.2 mm; 95% CI, 0.16-0.30 mm). CONCLUSIONS: There is no difference in the accuracy of superimposition of a stereophotogrammetry image with a 22 cm CBCT scan or a 13 cm CBCT scan. It should now be possible to use a 13 cm CBCT scan and a full-face stereophotogrammetry image during 3D orthognathic planning to reduce radiation exposure.

Anterior projection of the maxillomandibular soft tissue complex after surgical correction of maxillary hypoplasia: a Scottish perspective.

After orthognathic surgery the forehead remains unchanged. To produce facial harmony, the planned projection of the maxillomandibular complex must be placed in the correct relations to the unchanged position of the forehead. We have compared the anterior soft tissue projection of the maxillomandibular complex relative to the forehead after Le Fort I advancement surgery for correction of maxillary hypoplasia with that of a local reference group chosen by lay assessors. We retrospectively studied 32 patients (16 men and 16 women) all of whom had previously been treated by Le Fort I maxillary advancement. In addition a panel of 8 lay assessors selected a reference group of 24 women and 16 men. Standard profile photographs were taken, and horizontal measurements made, of several landmarks from a true vertical line (TV) passing through glabella. Together with facial harmony values these were compared between the groups. The orthognathic group had significantly more anterior mandibular projection relative to the forehead than the female reference group (p=0.03). As a result half of the horizontal harmony values were smaller in the orthognathic group. For men the position of the mandible, particularly the chin, was acceptable even though it was positioned more anteriorly. We have provided values for maxillomandibular projection derived from lay assessors and identified areas where differences from those of a reference group were detected. The projection of the mid and lower face of the local reference group to the forehead should guide preoperative planning.

How accurate are rapid prototyped (RP) final orthognathic surgical wafers? A pilot study.

Computer packages have been introduced to simulate the movements of the jaw in three dimensions to facilitate planning of treatment. After final 3-dimensional virtual planning, a rapid prototype wafer can be manufactured and used in theatre. Our aim was to assess the accuracy of rapid prototyping of virtual wafers derived from laser scanned dental models using CAD/CAM software. Upper and lower plaster models from 10 orthognathic patients, the articulated models, and the conventional wafers were scanned. The virtual wafers were made from CAD/CAM software, and printed on a stereolithographic printer. We also scanned the articulated models with rapid prototype wafers in place. The validity of the final rapid prototype wafer was measured by the accuracy with which upper and lower models related to one another. The absolute mean error of the rapid prototype wafer when aligned with the dental models was 0.94 (0.09) mm. The absolute distance of the 2 models articulated by conventional and rapid prototype wafers ranged from 0.04 - 1.73mm. The rapid prototype wafers were able to orientate the upper and lower dental models with an absolute mean error of 0.94 (0.09) mm, but it ranged from 0.04-1.73mm.

Comparison of the accuracy of voxel based registration and surface based registration for 3D assessment of surgical change following orthognathic surgery.

PURPOSE: Superimposition of two dimensional preoperative and postoperative facial images, including radiographs and photographs, are used to evaluate the surgical changes after orthognathic surgery. Recently, three dimensional (3D) imaging has been introduced allowing more accurate analysis of surgical changes. Surface based registration and voxel based registration are commonly used methods for 3D superimposition. The aim of this study was to evaluate and compare the accuracy of the two methods. MATERIALS AND METHODS: Pre-operative and 6 months post-operative cone beam CT scan (CBCT) images of 31 patients were randomly selected from the orthognathic patient database at the Dental Hospital and School, University of Glasgow, UK. Voxel based registration was performed on the DICOM images (Digital Imaging Communication in Medicine) using Maxilim software (Medicim-Medical Image Computing, Belgium). Surface based registration was performed on the soft and hard tissue 3D models using VRMesh (VirtualGrid, Bellevue City, WA). The accuracy of the superimposition was evaluated by measuring the mean value of the absolute distance between the two 3D image surfaces. The results were statistically analysed using a paired Student t-test, ANOVA with post-hoc Duncan test, a one sample t-test and Pearson correlation coefficient test. RESULTS: The results showed no significant statistical difference between the two superimposition methods (p<0.05). However surface based registration showed a high variability in the mean distances between the corresponding surfaces compared to voxel based registration, especially for soft tissue. Within each method there was a significant difference between superimposition of the soft and hard tissue models. CONCLUSIONS: There were no significant statistical differences between the two registration methods and it was unlikely to have any clinical significance. Voxel based registration was associated with less variability. Registering on the soft tissue in isolation from the hard tissue may not be a true reflection of the surgical change.

Validation of a computer modelled forensic facial reconstruction technique using CT data from live subjects: a pilot study.

INTRODUCTION: Human forensic facial soft tissue reconstructions are used when post-mortem deterioration makes identification difficult by usual means. The aim is to trigger recognition of the in vivo countenance of the individual by a friend or family member. A further use is in the field of archaeology. There are a number of different methods that can be applied to complete the facial reconstruction, ranging from two dimensional drawings, three dimensional clay models and now, with the advances of three dimensional technology, three dimensional computerised modelling. Studies carried out to assess the accuracy of facial reconstructions have produced variable results over the years. Advances in three dimensional imaging techniques in the field of oral and maxillofacial surgery, particularly cone beam computed tomography (CBCT), now provides an opportunity to utilise the data of live subjects and assess the accuracy of the three dimensional computerised facial reconstruction technique. AIM: The aim of this study was to assess the accuracy of a computer modelled facial reconstruction technique using CBCT data from live subjects. MATERIALS AND METHODS: This retrospective pilot study was carried out at the Glasgow Dental Hospital Orthodontic Department and the Centre of Anatomy and Human Identification, Dundee University School of Life Sciences. Ten patients (5 male and 5 female; mean age 23 years) with mild skeletal discrepancies with pre-surgical cone beam CT data (CBCT) were included in this study. The actual and forensic reconstruction soft tissues were analysed using 3D software to look at differences between landmarks, linear and angular measurements and surface meshes. RESULTS AND CONCLUSION: There were no statistical differences for 18 out of the 23 linear and 7 out of 8 angular measurements between the reconstruction and the target (p<0.05). The use of Procrustes superimposition has highlighted potential problems with soft tissue depth and anatomical landmarks' position. Surface mesh analysis showed that this virtual sculpture technique can be objectively assessed using the distance between the meshes. This study found that the percentage of faces with less than ±2.5mm error ranged from 56% to 90%. This may be improved if Procrustes superimposition could be applied to all the mesh points rather than specific landmarks.

Evaluation of an interactive multi-media device for delivering information on Le Fort I osteotomy.

This study was carried out on volunteers to evaluate a newly developed interactive software package aimed at informing prospective Le Fort I osteotomy patients regarding the surgical technique and possible complications. The aim of the study was to compare two methods of information delivery; a multi-media tablet device delivering both graphic and verbal information, and an audio device delivering essentially the same information in verbal form only. The null hypothesis was that there would be no difference between the efficiencies of the two methods. The subjects' ability to recall the information delivered by both devices was assessed using a questionnaire. The tablet device participants scored an average of 15.48 points, while the audio device participants scored an average of 268 points. The difference was statistically significant (p < 0.001), suggesting that the multi-media tablet device was more effective method.

Subjective versus objective assessment of breast reconstruction.

BACKGROUND: To date breast assessment has been conducted mainly subjectively. However lately validated objective three-dimensional (3D) imaging was developed. The study aimed to assess breast reconstruction subjectively and objectively and conduct a comparison. METHODS: In forty-four patients after immediate unilateral breast reconstruction with solely the extended latissimus dorsi flap the breast was captured by validated 3D imaging method and standardized 2D photography. Breast symmetry was subjectively evaluated by six experts who applied the Harris score giving a mark of 1-4 for a poor to excellent result. An error study was conducted by examination of the intra and inter-observer agreement and agreement on controls. By Procrustes analysis an objective asymmetry score was obtained and compared to the subjective assessment. RESULTS: The subjective assessment showed that the inter-observer agreement was good or substantial (p-value: <0.0001). There was moderate agreement on the controls (p-value: <0.0001) and fair (p-values: 0.159, 0.134, 0.099) to substantial (p-value: 0.005) intra-observer agreement. The objective assessment revealed that the reconstructed breast showed a significantly smaller volume compared to the opposite side and that the average asymmetry score was 0.052, ranging from 0.019 to 0.136. When comparing the subjective and objective method the relationship between the two scores was highly significant. CONCLUSION: Subjective breast assessment lacked accuracy and reproducibility. This was the first error study of subjective breast assessment versus an objective validated 3D imaging method based on true 3D parameters. The substantial agreement between established subjective breast assessment and new validated objective method supported the value of the later and we expect its future role to expand.