scholarly journals Accuracy of three-dimensional photogrammetry and cone beam computed tomography based on linear measurements in patients with facial deformities

2020 ◽  
pp. 20200001
Author(s):  
Zhenqi Zhao ◽  
Lizhe Xie ◽  
Dan Cao ◽  
Iman Izadikhah ◽  
Pengcheng Gao ◽  
...  
Keyword(s):  
Reference Values ◽  
Measurement Errors ◽  
Three Dimensional ◽  
Coordinate Measuring Machine ◽  
Cone Beam ◽  
Reference Systems ◽  
Linear Measurements ◽  
3D Photogrammetry ◽  
Measuring Machine ◽  
Linear Accuracy

Objectives: This study was aimed to investigate the accuracy of soft-tissue measurements obtained by two imaging modalities, three-dimensional (3D) photogrammetry and cone beam CT (CBCT) when confounded by influence factors (facial deformities and partitions). Methods: 60 wax facial models from facially deformed patients were captured by 3D photogrammetry and CBCT. 19 linear distances on each image were measured and juxtaposed to reference values attained via a coordinate-measuring machine (CMM) as the gold-standard. Paired t-tests were used to compare linear accuracy of the test and reference systems. The influence of deformities and partitions (created by dividing the face with three vertical and five horizontal lines) on the measurement errors were analyzed by independent sample t-test and one-way ANOVA. Results: Statistically significant differences were found between linear accuracy of the test and reference systems. The test values obtained by 3D photogrammetry were closer to the reference values than CBCT’s. 3D photogrammetry’s measurement errors were significantly higher in deformed areas, unlike CBCT’s. Both systems reported significantly lower errors within partitions 8 and 13 compared to other partitions; for CBCT, aside from partitions 8 and 13, the differences in the errors for partitions 6 and 10 were significant compared to partitions 8, 12, 13, 14. Conclusion: 3D photogrammetry showed a higher linear accuracy than CBCT in patients with facial deformities due to protuberances. Facial reconstruction by both test modalities was significantly influenced in different facial partitions, but facial deformities extensively affected the results from 3D photogrammetry.

Trueness and Precision of Three Different Scanners for Digitizing a Completely Edentulous Gypsum Model

2021 ◽  
Vol 11 (1) ◽  
pp. 89-95
Author(s):  
Ammar Kayssoun ◽  
A. Nehir Özden
Keyword(s):  
Computed Tomography ◽  
Statistical Significance ◽  
Three Dimensional ◽  
Coordinate Measuring Machine ◽  
Cone Beam ◽  
Intraoral Scanner ◽  
Measuring Machine ◽  
The Mean ◽  
One Way Anova

Purpose: The aim of this in vitro study was to evaluate the precision and trueness of three different scanners to scan a maxillary edentulous model using three-dimensional evaluation software. Materials and Methods: A coordinate measuring machine was used as the reference scanner. Cone beam computed tomography, computed tomography (CT), and an intraoral scanner were used to digitize an edentulous gypsum model. Data were collected and loaded into three-dimensional evaluation software. The scan outputs were superimposed, and the accuracy (trueness and precision) of the scanners were compared. One-way ANOVA was used to compare the accuracy values among all groups (trueness) and to determine differences within groups (precision). Statistical significance was assessed with an independent sample t-test (= 0.05) for each group. Results: The mean precision values ranged from 3.5 to –0.2 m. Analysis of the superimposed scans onto the reference scan for each group revealed no significant differences in trueness and precision (p > 0.05) among all groups. Further, binary comparisons of the datasets of each group revealed no significant differences (p > 0.05) in terms of precision values, except in the CT group wherein significant differences (p ≤ 0.05) were observed for most models. Conclusions: No significant differences were observed in terms of accuracy (precision and trueness) among the three scanners. All scanners were effective in scanning the edentulous gypsum model.

Evaluation of Parts Produced by a Novel Additive Manufacturing Process

2013 ◽  
Vol 315 ◽  
pp. 63-67 ◽  
Author(s):  
Muhammad Fahad ◽  
Neil Hopkinson
Keyword(s):  
Additive Manufacturing ◽  
Rapid Prototyping ◽  
Manufacturing Process ◽  
High Speed ◽  
Three Dimensional ◽  
Coordinate Measuring Machine ◽  
Layer By Layer ◽  
Nylon 12 ◽  
Measuring Machine ◽  
End Use

Rapid prototyping refers to building three dimensional parts in a tool-less, layer by layer manner using the CAD geometry of the part. Additive Manufacturing (AM) is the name given to the application of rapid prototyping technologies to produce functional, end use items. Since AM is relatively new area of manufacturing processes, various processes are being developed and analyzed for their performance (mainly speed and accuracy). This paper deals with the design of a new benchmark part to analyze the flatness of parts produced on High Speed Sintering (HSS) which is a novel Additive Manufacturing process and is currently being developed at Loughborough University. The designed benchmark part comprised of various features such as cubes, holes, cylinders, spheres and cones on a flat base and the build material used for these parts was nylon 12 powder. Flatness and curvature of the base of these parts were measured using a coordinate measuring machine (CMM) and the results are discussed in relation to the operating parameters of the process.The result show changes in the flatness of part with the depth of part in the bed which is attributed to the thermal gradient within the build envelope during build.

Surface Texture Measurement with Profile Method Using Six-Axis Coordinate Measuring Machine

2021 ◽  
Vol 410 ◽  
pp. 872-877
Author(s):  
Andrey V. Kochetkov ◽  
Andrey A. Troshin ◽  
Oleg V. Zakharov
Keyword(s):  
Surface Texture ◽  
Measurement Errors ◽  
Coordinate Measuring Machine ◽  
Texture Measurement ◽  
Analytical Geometry ◽  
Complex Shapes ◽  
Measurement Results ◽  
Measuring Machine ◽  
Cartesian Coordinate ◽  
Filtering Effect

Currently the measurement of surface texture in mechanical engineering is traditionally carried out using profilometers. Modern profilometers do not allow measuring of surfaces with complex shapes. This is due to the different sensitivity of the sensor and the discreteness of the movements along the axes of the Cartesian coordinate system. Coordinate Measuring Machines are devoid of such a drawback. However, stylus of the coordinate measuring machine has a diameter many times larger than the diamond stylus of the profilometer. Therefore, there is a mechanical filtering effect, that affects the results of measuring the parameters of the surface texture. In this paper a mathematical model of the contact of the spherical stylus and a rough surface based on analytical geometry is proposed. Influence of the diameter of the spherical stylus on the maximum measurement errors of a amplitude parameters are investigated. Seven amplitude parameters Rp, Rv, Rz, Ra, Rq, Rsk, Rku of the surface texture are modeled. Coordinate measuring machine and profilometer with stylus diameter of 2 μm measurement results are compared. it was concluded that the stylus diameter of the coordinate measuring machine when measuring the surface texture should be no more than 20 μm.

scholarly journals Enabling Technology for Remote Prosthetic Alignment Tuning

2021 ◽  
Vol 186 (Supplement_1) ◽  
pp. 659-664
Author(s):  
David A Boone ◽  
Sarah R Chang
Keyword(s):  
Machine Learning ◽  
Learning Algorithm ◽  
Three Dimensional ◽  
Coordinate Measuring Machine ◽  
Software Application ◽  
Prosthetic Socket ◽  
Prosthetic Alignment ◽  
Prosthesis Alignment ◽  
Alignment Tool ◽  
Measuring Machine

ABSTRACT Introduction This research has resulted in a system of sensors and software for effectively adjusting prosthetic alignment with digital numeric control. We called this suite of technologies the Prosthesis Smart Alignment Tool (ProSAT) system. Materials and Methods The ProSAT system has three components: a prosthesis-embedded sensor, an alignment tool, and an Internet-connected alignment expert system application that utilizes machine learning to analyze prosthetic alignment. All components communicate via Bluetooth. Together, they provide for numerically controlled prosthesis alignment adjustment. The ProSAT components help diagnose and guide the correction of very subtle, difficult-to-see imbalances in dynamic gait. The sensor has been cross-validated against kinetic measurement in a gait laboratory, and bench testing was performed to validate the performance of the tool while adjusting a prosthetic socket based on machine learning analyses from the software application. Results The three-dimensional alignment of the prosthetic socket was measured pre- and postadjustment from two fiducial points marked on the anterior surface of the prosthetic socket. A coordinate measuring machine was used to derive an alignment angular offset from vertical for both conditions: pre- and postalignment conditions. Of interest is the difference in the angles between conditions. The ProSAT tool is only controlling the relative change made to the alignment, not an absolute position or orientation. Target alignments were calculated by the machine learning algorithm in the ProSAT software, based on input of kinetic data samples representing the precondition and where a real prosthetic misalignment condition was known a priori. Detected misalignments were converted by the software to a corrective adjustment in the prosthesis alignment being tested. We demonstrated that a user could successfully and quickly achieve target postalignment change within an average of 0.1°. Conclusions The accuracy of a prototype ProSAT system has been validated for controlled alignment changes by a prosthetist. Refinement of the ergonomic form and technical function of the hardware and clinical usability of the mobile software application are currently being completed with benchtop experiments in advance of further human subject testing of alignment efficiency, accuracy, and user experience.

Evaluation of Actual Geometric Tolerances Using Coordinate Measuring Machine Data

1989 ◽  
Author(s):  
W. H. ElMaraghy ◽  
Z. Wu ◽  
H. A. ElMaraghy
Keyword(s):  
Three Dimensional ◽  
Measurement Data ◽  
Simulated Data ◽  
Coordinate Measuring Machine ◽  
Optimization Techniques ◽  
Test Cases ◽  
Tolerance Zone ◽  
Geometric Tolerances ◽  
Measuring Machine

Abstract This paper focuses on the development of a procedure and algorithms for the systematic comparison of geometric variations of measured features with their specified geometric tolerances. To automate the inspection of mechanical parts, it is necessary to analyze the measurement data captured by coordinate measuring machines (CMM) in order to detect out-of-tolerance conditions. A procedure for determining the geometric tolerances from the measured three dimensional coordinates on the surface of a cylindrical feature is presented. This procedure follows the definitions of the geometric tolerances used in the current Standards, and is capable of determining the value of each geometric tolerance from the composite 3-D data. The developed algorithms adopt the minimum tolerance zone criterion. Nonlinear numerical optimization techniques are used to fit the data to the minimum tolerance zone. Two test cases are given in the paper which demonstrate the successful determination of geometric tolerances from given simulated data.

scholarly journals Cone Beam Computed Tomography 3D Reconstruction of the Mandibular Condyle

2008 ◽  
Vol 78 (5) ◽  
pp. 880-888 ◽  
Author(s):  
Brian Schlueter ◽  
Ki Beom Kim ◽  
Donald Oliver ◽  
Gus Sortiropoulos
Keyword(s):  
Computed Tomography ◽  
Soft Tissue ◽  
3D Reconstruction ◽  
Cone Beam Computed Tomography ◽  
Three Dimensional ◽  
Mandibular Condyle ◽  
Cone Beam ◽  
Low Density ◽  
Mineral Density ◽  
Linear Measurements

Abstract Objective: To determine the ideal window level and width needed for cone beam computed three-dimensional (3D) reconstruction of the condyle. Materials and Methods: Linear dimensions were measured with a digital caliper to assess the anatomic truth for 50 dry human mandibular condyles. Condyles were scanned with the i-CAT cone beam computed tomography (CBCT) and 3D-models were reconstructed. Three linear three-dimensional measurements were made on each of the 50 condyles at 8 different Hounsfield unit (HU) windows. These measurements were compared with the anatomic truth. Volumetric measurements were also completed on all 50 condyles, at 23 different window levels, to define the volumetric distribution of bone mineral density (BMD) within the condyle. Results: Significant differences were found in two of the three linear measurement groups at and below the recommended viewing window for osseous structures. The most accurate measurements were made within the soft tissue range for HU window levels. Volumetric distribution measurements revealed that the condyles were mostly comprised of low-density bone, and that condyles exhibiting significant changes in linear measurements were shown to have higher percentages of low-density bone than those condyles with little change from the anatomic truth. Conclusions: CBCT assessment of the mandibular condyle, using the 3D reconstruction, is most accurate when accomplished at density levels below that recommended for osseous examination. However, utilizing lower window levels which extend into the soft tissue range, may compromise one's capacity to view the bony topography.

scholarly journals Cephalometric measurements from 3D reconstructed images compared with conventional 2D images

2011 ◽  
Vol 81 (5) ◽  
pp. 856-864 ◽  
Author(s):  
Natalia Zamora ◽  
Jose M. Llamas ◽  
Rosa Cibrián ◽  
Jose L. Gandia ◽  
Vanessa Paredes
Keyword(s):  
Three Dimensional ◽  
Cone Beam ◽  
Two Dimensional ◽  
Linear Measurements ◽  
3D Reconstructions ◽  
Software Packages ◽  
Mandibular Plane ◽  
Different Types ◽  
Cephalometric Measurements ◽  
2D Images

Abstract Objective: To assess whether the values of different measurements taken on three-dimensional (3D) reconstructions from cone-beam computed tomography (CBCT) are comparable with those taken on two-dimensional (2D) images from conventional lateral cephalometric radiographs (LCRs) and to examine if there are differences between the different types of CBCT software when taking those measurements. Material and Methods: Eight patients were selected who had both an LRC and a CBCT. The 3D reconstructions of each patient in the CBCT were evaluated using two different software packages, NemoCeph 3D and InVivo5. An observer took 10 angular and 3 linear measurements on each of the three types of record on two different occasions. Results: Intraobserver reliability was high except for the mandibular plane and facial cone (from the LCR), the Na-Ans distance (using NemoCeph 3D), and facial cone and the Ans-Me distance (using InVivo5). No statistically significant differences were found for the angular and linear measurements between the LCRs and the CBCTs for any measurement, and the correlation levels were high for all measurements. Conclusion: No statistically significant differences were found between the angular and linear measurements taken with the LCR and those taken with the CBCT. Neither were there any statistically significant differences between the angular or linear measurements using the two CBCT software packages.

scholarly journals Taurodontism and Van der Woude Syndrome

2008 ◽  
Vol 78 (5) ◽  
pp. 832-837 ◽  
Author(s):  
Hiroyuki Nawa ◽  
Snehlata Oberoi ◽  
Karin Vargervik
Keyword(s):  
Clinical Sample ◽  
Cone Beam Ct ◽  
Three Dimensional ◽  
Panoramic Radiograph ◽  
Cross Sectional Study ◽  
Cone Beam ◽  
Linear Measurements ◽  
Van Der Woude Syndrome ◽  
Cross Sectional ◽  
Mandibular First Molar

Abstract Objective: To report the occurrence of taurodontism in a clinical sample of Van der Woude syndrome (VWS) and describe its association with hypodontia and cleft type. Materials and Methods: This retrospective, cross-sectional study was carried out on chart reviews and radiographs of 13 persons with VWS. Mean age was 10 years 11 months ± 1 year 5 months. Panoramic radiographs were used to confirm the presence or absence of teeth and to measure crown body and root lengths of mandibular first molars. Three-dimensional cone beam computed tomography (CT) scans were available on two persons with VWS. Both volumetric and linear measurements were obtained. Results: The occurrence of taurodontism of the mandibular first molar was 35%: 27% hypodont and 8% mesodont. Of the 13 subjects with VWS, 6 (4 males and 2 females) had at least one tooth identified with taurodontism. Half of the cases were unilateral and half were bilateral, and all of the unilateral cases were on the left side. Five of the six subjects with taurodontism had missing incisors and premolars. Taurodontism was two times more frequent in those who were missing their second premolars than in those who had their second premolars. There was no correlation between cleft type and presence of taurodontism. The cone beam CT pilot study on two persons showed very abnormal morphology of both crown and roots, which was not apparent on the standard panoramic radiograph. Both the volumetric and linear measurements of the ratio of crown body to root were highly indicative of taurodontism. Further genetic studies are needed. Conclusion: There is a likely association between VWS and taurodontism.

scholarly journals Trueness and Precision of Three-Dimensional Digitizing Intraoral Devices

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Hussam Mutwalli ◽  
Michael Braian ◽  
Deyar Mahmood ◽  
Christel Larsson
Keyword(s):  
Three Dimensional ◽  
Coordinate Measuring Machine ◽  
In Vitro Study ◽  
Vitro Study ◽  
Distance Measurements ◽  
True Value ◽  
Measuring Machine ◽  
One Way Anova ◽  
Intraoral Devices

Aim. To measure the trueness and precision under repeatable conditions for different intraoral scanners (IOSs) when scanning fully edentulous arch with multiple implants. Materials and Methods. Three IOSs and one industrial scanner were used to scan one edentulous master cast containing five implant scan bodies and three spheres. The cast was scanned thirty times with each scanner device. All scans were analyzed in the inspect software, and three-dimensional locations of the implants and the interarch distance between the spheres were measured. The values were compared to measurements made with one coordinate measuring machine (true value). One-way ANOVA was used to calculate the differences between IOSs and in comparison with the true value. Results. Significant differences were found between all IOSs. For the implant measurements, Trios 3 had the lowest trueness (≤114 μm), followed by Trios 3 mono (≤63 μm) and Itero element (≤−41 μm). Trios had the lowest precision (≤135 μm), followed by Itero element (≤101 μm) and Trios 3 mono (≤100 μm). With regard to the interarch distance measurements, Trios 3 had the lowest trueness (≤68 μm), followed by Trios 3 mono (≤45 μm) and Itero element (≤40 μm). Trios 3 had the lowest precision (≤206 μm), followed by Itero element (≤124 μm) and Trios 3 mono (≤111 μm). Conclusion. The results from this in vitro study suggest that precision is low for the tested IOS devices when scanning fully edentulous arches with multiple implants.

scholarly journals 3D DIGITIZING TECHNOLOGY IN PRODUCT REVERSE DESIGN

2011 ◽  
Author(s):  
Qingjin Peng ◽  
Hector Sanchez
Keyword(s):  
Shape Recovery ◽  
Three Dimensional ◽  
Laser Scanner ◽  
Coordinate Measuring Machine ◽  
Cost Effective ◽  
3D Shape ◽  
3D Data ◽  
Cost Effective Approach ◽  
Measuring Machine ◽  
And Performance

The reverse design develops new products based on the improvement of existing products. The shape recovery of three-dimensional (3D) objects is the basis of the product reverse design. 3D digitization technology is an important tool for the 3D shape recovery. This paper analyses the current 3D data acquisition technology. The accuracy and performance of the 3D laser scanner is evaluated. A cost-effective approach is proposed to recover 3D shape of objects using a structured-light technique. Details of the proposed method are described. Application examples are presented. The accuracy is evaluated using a coordinate measuring machine.

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