The virtual human face – superimposing the simultaneously captured 3D photorealistic skin surface of the face on the untextured skin image of the CBCT Scan

The aim of this study was to evaluate the impact of simultaneous capture of the three-dimensional (3D) surface of the face and cone beam computed tomography (CBCT) scan of the skull on the accuracy of their registration and superimposition. 3D facial images were acquired in 14 patients using the Di3d (Dimensional Imaging, UK) imaging system and i-CAT CBCT scanner. One stereophotogrammetry image was captured at the same time as the CBCT and another one hour later. The two stereophotographs were then individually superimposed over the CBCT using VRmesh. Seven patches were isolated on the final merged surfaces. For the whole face and each individual patch; maximum and minimum range of deviation between surfaces, absolute average distance between surfaces, and standard deviation for the 90th percentile of the distance errors were calculated. The superimposition errors of the whole face for both captures revealed statistically significant differences (P=0.00081). The absolute average distances in both separate and simultaneous captures were 0.47mm and 0.27mm, respectively. The level of superimposition accuracy in patches from separate captures ranged between 0.3 and 0.9mm, while that of simultaneous captures was 0.4mm. Simultaneous capture of Di3d and CBCT images significantly improved the accuracy of superimposition of these image modalities

How accurate are the fusion of Cone-beam CT and 3-D stereophotographic images?

Background: Cone-beam Computed Tomography (CBCT) and stereophotography are two of the latest imaging modalities available for three-dimensional (3-D) visualization of craniofacial structures. However, CBCT provides only limited information on surface texture. This can be overcome by combining the bone images derived from CBCT with 3-D photographs. The objectives of this study were 1) to evaluate the feasibility of integrating 3-D Photos and CBCT images 2) to assess degree of error that may occur during the above processes and 3) to identify facial regions that would be most appropriate for 3-D image registration. Methodology: CBCT scans and stereophotographic images from 29 patients were used for this study. Two 3-D images corresponding to the skin and bone were extracted from the CBCT data. The 3-D photo was superimposed on the CBCT skin image using relatively immobile areas of the face as a reference. 3-D colour maps were used to assess the accuracy of superimposition were distance differences between the CBCT and 3-D photo were recorded as the signed average and the Root Mean Square (RMS) error. Principal Findings: The signed average and RMS of the distance differences between the registered surfaces were -0.018 (±0.129) mm and 0.739 (±0.239) mm respectively. The most errors were found in areas surrounding the lips and the eyes, while minimal errors were noted in the forehead, root of the nose and zygoma. Conclusions: CBCT and 3-D photographic data can be successfully fused with minimal errors. When compared to RMS, the signed average was found to under-represent the registration error. The virtual 3-D composite craniofacial models permit concurrent assessment of bone and soft tissues during diagnosis and treatment planning. © 2012 Jayaratne et al.published_or_final_versio

A pilot study for the digital replacement of a distorted dentition acquired by Cone Beam Computed Tomography (CBCT)

Abstract Introduction: Cone beam CT (CBCT) is becoming a routine imaging modality designed for the maxillofacial region. Imaging patients with intra-oral metallic objects cause streak artefacts. Artefacts impair any virtual model by obliterating the teeth. This is a major obstacle for occlusal registration and the fabrication of orthognathic wafers to guide the surgical correction of dentofacial deformities. Aims and Objectives: To develop a method of replacing the inaccurate CBCT images of the dentition with an accurate representation and test the feasibility of the technique in the clinical environment. Materials and Method: Impressions of the teeth are acquired and acrylic baseplates constructed on dental casts incorporating radiopaque registration markers. The appliances are fitted and a preoperative CBCT is performed. Impressions are taken of the dentition with the devices in situ and subsequent dental models produced. The models are scanned to produce a virtual model. Both images of the patient and the model are imported into a virtual reality software program and aligned on the virtual markers. This allows the alignment of the dentition without relying on the teeth for superimposition. The occlusal surfaces of the dentition can be replaced with the occlusal image of the model. Results: The absolute mean distance of the mesh between the markers in the skulls was in the region of 0.09mm ± 0.03mm; the replacement dentition had an absolute mean distance of about 0.24mm ± 0.09mm. In patients the absolute mean distance between markers increased to 0.14mm ± 0.03mm. It was not possible to establish the discrepancies in the patient’s dentition, since the original image of the dentition is inherently inaccurate. Conclusion: It is possible to replace the CBCT virtual dentition of cadaveric skulls with an accurate representation to create a composite skull. The feasibility study was successful in the clinical arena. This could be a significant advancement in the accuracy of surgical prediction planning, with the ultimate goal of fabrication of a physical orthognathic wafer using reverse engineering

How to Obtain an Orthodontic Virtual Patient through Superimposition of Three-Dimensional Data: A Systematic Review

Background: This systematic review summarizes the current knowledge on the superimposition of three-dimensional (3D) diagnostic records to realize an orthodontic virtual patient. The aim of this study is to analyze the accuracy of the state-of-the-art digital workflow. Methods: The research was carried out by an electronic and manual query eectuated from ISS (Istituto Superiore di Sanit\ue0 in Rome) on three dierent databases (MEDLINE, Cochrane Library and ISI WEB OF SCIENCE) up to 31st January 2020. The search focused on studies that superimposed at least two dierent 3D records to build up a 3D virtual patient\u2014information about the devices used to acquire 3D data, the software used to match data and the superimposition method applied have been summarized. Results: 1374 titles were retrieved from the electronic search. After title-abstract screening, 65 studies were selected. After full-text analysis, 21 studies were included in the review. Dierent 3D datasets were used: facial skeleton (FS), extraoral soft tissues (ST) and dentition (DENT). The information provided by the 3D data was superimposed in four dierent combinations: FS + DENT (13 papers), FS + ST (5 papers), ST + DENT (2 papers) and all the types (FS + ST + DENT) (1 paper). Conclusions: The surface-based method was most frequently used for 3D objects superimposition (11 papers), followed by the point-based method (6 papers), with or without fiducial markers, and the voxel-based method (1 paper). Most of the papers analyzed the accuracy of the superimposition procedure (15 papers), while the remaining were proof-of-principles (10 papers) or compared dierent methods (3 papers). Further studies should focus on the definition of a gold standard. The patient is going to have a huge advantage from complete digital planning when more information about the spatial relationship of anatomical structures are needed: ectopic, impacted and supernumerary teeth, root resorption and angulations, cleft lip and palate (CL/P), alveolar boundary conditions, periodontally compromised patients, temporary anchorage devices (TADs), maxillary transverse deficiency, airway analyses, obstructive sleep apnea (OSAS), TMJ disorders and orthognathic and cranio-facial surgery

Digital Era of Orthodontics: A Review

Orthodontic treatment is a complex dental treatment which sometimes requires an interdisciplinary team where different specialists of dental medicine have to manage a vast quantity of data especially in adult orthodontics. In such complicated cases, good diagnostic tools and easy communication are essential. Computer science has an increasing impact in almost every aspect of the orthodontic practice. This review will discuss into the said aspects in the practice of orthodontics as well as evaluate the applications of computer technology in orthodontics like digital photographs, cone beam computed tomography, virtual study models, communication, three-dimensional craniofacial imaging, virtual reality softwares for prediction and treatment planning, video imaging, manufacture of orthodontic appliance, web-based digital orthodontic records and network-attached storage devices

Digital dental splints in orthognathic surgery and evaluation of their accuracy of fit in an anatomically articulated model

PURPOSE: The purpose of this prospective clinical study is to evaluate the accuracy of fit of digital dental splints in an anatomically articulated model on which model surgery is performed. The intermediate 3D printed splints were verified in an anatomical articulator. MATERIALS AND METHODS: A total of 4 patients (Table 1,2) who were willing to undergo orthognathic surgery (Graph 2) were included in this study. The methodology of the study were as follows: A Cone Beam Computed Tomography scan was obtained with fiducial titanium markers of standardized dimensions glued to the attached gingiva (Figure 57) for all patients excluding one patient for whom a medical Computed Tomography scan was taken. The upper and lower impressions were made, and models prepared (Figure 58). These dental casts were scanned with an optical scanner and the digital dental casts were saved as stl files (Figure 56 A, B). The CBCT scans and the digital dental scans were imported into MIMICS software (Version 17.0 Leuven, Belgium). Planned virtual osteotomy was performed virtually on the 3D reconstructed models after accurate superimposition based on the fiducial titanium markers (Figure 30,31). Intermediate splints were virtually designed (Figure 36,37,38), and 3D printed by importing into 3D printer (Inkjet printing) in our study. RESULTS: Out of the four patients, one patient with Hemifacial Microsomia had extensive bleeding during a medial cut on the mandibular ramus due to which the planned mandibular surgery was not performed. One patient was previously treated for temporomandibular joint ankylosis, who had no complications intra-operatively during orthognathic surgery. The fit of the digital dental splint was subjectively superior to the conventional acrylic splints and therefore was clinically more acceptable. CONCLUSION: The results of this study indicates that virtual planning and 3D printing of the intermediate splints have the following advantages: 1. An overall decrease in the time required for conventional planning in orthognathic surgery. 2. Aids in better understanding of the existing deformity in all dimensions. 3. Ensures more accuracy in splint fabrication, aiding in superior precision in positioning of the osteotomized segments. 4. Minimizes the errors due to conventional two-dimensional radiographs. 5. The use of fiducial markers in our study makes the superimposition process more accurate and avoids inaccuracies due to superimposition