Scan Files Research Articles

Error analysis of stages involved in CBCT-guided implant placement with surgical guides when different printing technologies are used

Statement of problemDigital light processing (DLP), continuous liquid interface printing (CLIP), and stereolithography (SLA) technologies enable 3-dimensional (3D) printing of surgical guides. However, how their accuracy compares and how accuracy may affect subsequent steps in guided surgery is unclear. PurposeThe purpose of this in vitro study was to investigate the fabrication and seating accuracy of surgical guides printed by using DLP, SLA, and CLIP technologies and evaluate the positional deviation of the osteotomy site and placed implant compared with the digital implant plan. Material and methodsTwenty-one polyurethane models were divided into 3 groups and used to plan implants and design surgical guides. The guides were fabricated by using DLP, SLA, or CLIP 3D printers (n=7) and scanned, and the scan file was compared with the digital design file to analyze the fabrication accuracy at the intaglio and overall external surfaces using root mean square (RMS) values. The triple scan protocol was used to evaluate the seating accuracy of the guides on their respective models. Osteotomies were prepared on models by using the guides followed by a microcomputed tomography image of each osteotomy. The implants were placed through the guides, the scan bodies were tightened to implants, and the models were scanned to obtain the images of placed implant position. Osteotomy and placed implant images were used to calculate the entry point, apex, and long axis deviations from the planned implant position with a software program. A 2-way repeated-measures ANOVA of the RMS data was used to analyze printing and seating trueness, and homogeneity of variance analyses were used at each surface for precision. A 3-way repeated-measures ANOVA was used to analyze distance deviations over the stages (osteotomy and final implant) and locations studied, and a 2-way repeated-measures ANOVA was used for angular deviations. Homogeneity of variance analyses were performed for precision (α=.05). ResultsThe 3D printer type significantly affected the trueness of the guide at the intaglio surface (P<.001). SLA guides had the lowest mean RMS (59.04 μm) for intaglio surface, while CLIP had the highest mean RMS (117.14 μm). Guides from all 3D printers had low variability among measured deviations and therefore were similarly precise. The seating accuracy of SLA and DLP guides was not significantly different, but both had lower mean RMS values than CLIP (P=.003 for SLA, P=.014 for DLP). There were no significant interactions between the stage of surgery, the printer type, or the location of implant deviation (P=.734). Only the location of deviation (cervical versus apical) had a significant effect on distance deviations (P<.001). The printer type, stage of surgery, and their interaction did not significantly affect angular deviations (P=.41). ConclusionsThe 3D printing technology affected printing trueness. The intaglio surface trueness was higher with SLA and overall trueness was higher with the CLIP printer. The precision of all guides was similarly high. Guides from SLA and DLP printers had more accurate seating than those from CLIP. Higher deviations were observed at the apex; however, osteotomy and final implant position did not significantly differ from the digitally planned position.

Digital workflow in implant prosthodontics: The critical aspects for reliable accuracy.

This paper is a comprehensive treaty about the variables that influence the transfer of the position of an implant to the laboratory when using a digital workflow. The aim is to provide operators and manufacturers with a guide on how to improve certain aspects of the digital workflow specific to the fabrication of implant-supported restorations. It addresses intraoral scanning issues and CAD software issues. In the former, the variables that play a part in the quality of the scan file are investigated: the implant scan body, the IOS and the operator. For the latter, instead, the focus is on those aspects that still today may create inaccuracies in the workflow and in the final product being fabricated: the identification of the specific implant placed in the patient and the generation of a virtual model with the representation of that implant platform correctly positioned in the three dimensions of space. Suggestions and recommendations are given to improve the control on the quality of the digital workflow's output. In a digital workflow for the fabrication of an implant-supported restoration, the selection and use of the implant scan body, the use of an effective scan strategy and the appropriateness of the best fit function in the CAD software, that is, the procedure of superimposing the library of geometric shapes of the ISB linked to the implant with the shape acquired intraorally, are variables that can influence the positional precision of the FDP. Fully understanding the importance of the information enclosed in the ISBs themselves can be crucial in the digital workflow. A proper ISB's selection, a correct scan of the ISB's shape and an accurate CAD superimposition of the ISB's library can lead the clinician to reduce the variables that affect the final result in daily practice.

Automated Classification of Whole-Body SPECT Bone Scan Images with VGG-Based Deep Networks

Single Photon Emission Computed Tomography (SPECT) imaging has the potential to acquire information about areas of concerns in a non-invasive manner. Until now, however, deep learning based classification of SPECT images is still not studied yet. To examine the ability of convolutional neural networks on classifying whole-body SPECT bone scan images, in this work, we propose three different two-class classifiers based on the classical Visual Geometry Group (VGG) model. The proposed classifiers are able to automatically identify that whether or not a SPECT image include lesions via classifying this image into categories. Specifically, a pre-processing method is proposed to convert each SPECT file into an image via balancing difference of the detected uptake between SPECT files, normalizing elements of each file into an interval, and splitting an image into batches. Second, different strategies were introduced into the classical VGG 16 model to develop classifiers by minimizing the number of parameters as many as possible. Lastly, a group of clinical whole-body SPECT bone scan files were utilized to evaluate the developed classifiers. Experiment results show that our classifiers are workable for automated classification of SPECT images, obtaining the best values of 0.838, 0.929, 0.966, 0.908 and 0.875 for accuracy, precision, recall, F-1 score and AUC value, respectively.

3D Modeling the Work Space with a Lidar Sensor-Supported Camera and Designing the Designs with Genius Loci Concept in Design Programs

Furniture, colors and designs used in work spaces affect working performance and quality of working life. This study works with the Genius Loci concept, which expresses the original atmosphere and air of the work space. The work space was scanned with a lidar sensor-supported camera as part of the study. The obtained scanning file was transferred to a computer platform and made usable with the relevant design program. The relevant design program made it easy to adjust and see the positive effects of the changes in the re-designed work space on work performance and the person using the work space after the changes in the re-designed work space were implemented. By referencing this study, the positive direct effect on performance increase in work space can be seen in the re-designed work space.

Is Intraoral Scanning Accurate to Evaluate Dental Implant Position? An In-Vitro Study

The position of dental implants is generally verified through imaging exams, even though its use exposes patients to radiation. Intraoral scanning (IOS) may be a suitable alternative to using radiographic imaging to verify implant position. Using polyurethane jaw models, the purpose of this in-vitro study was to measure and compare implant positions determined by IOS and cone-bean computed tomography (CBCT). One hundred twenty implants were installed in 30 edentulous polyurethane jaws, 4 dental implants in each prototype. Four scanbodies were attached to the implants, and a scanning of each mandible was acquired using an intraoral scanner (CS 3600). All prototypes were also submitted to CBCT. Then, the 3D scan files in STL (Standard Tessellation Language) format were superimposed on the DICOM (Digital Imaging and Communications in Medicine) images of the tomographic mandibles. The accuracy of IOS was evaluated by the metric analyses of deviations between the position of the implants projected by the IOS versus the detected tomographically, in which CBCT served as the gold standard, using a free software for digital planning (Bluesky 4 - Grayslake, IL, USA). The following measures were analyzed: radial deviations at the shoulder (Xc) and at the apex of the implants (Xa), height deviation (Xh) and axial deviation. Bland-Altman and a paired t-test were applied to verify the reproducibility between measurements and a t-test for a mean was applied to compare the measurements with zero value. The results showed Xc and Xa deviation means of 0.14±0.09mm and 0.12±0.12mm, respectively. The Xh mean was 0.2±0.12mm and the axial deviation mean was 0.71°±0.66°. T-test showed a statistically significant difference when the 4 means were compared to zero value, represented by the CBCT (P<.0001). There was a statistically significant difference IN the scanned measures compared to CBCT as the standard, but the differences may not be clinically significant. The IOS utilization to evaluate the position of dental implants is a radiation-free and reproducible method, with the advantage of not generating metal artifacts. Further clinical studies are needed to validate this new method of postoperative evaluation.

Use of Digital Articulator in Implant Supported Prosthetics. A Case Report

Introduction: A case report is presented to demonstrate advantages of a new fully digital approach, from planning through to execution to immediate loading implant-prosthetic rehabilitation. Until now, the function of the diagnostic wax-up has not been assessable and the functionalization of the finished product, be it either a provisional or a definitive, has been entrusted entirely to the ability of the technician. Case Description: A female patient, unaffected by systemic disease and cranio-cervico-mandibular muscular pain, required removal of hopeless residual teeth of the upper arch and substitution with immediately loaded implants using guided surgery. A fully digital technique was performed using specific software to record individual condylar (axiography) movements and mastication cycles and to correlate these with initial intra-oral scans in order to create a virtual 3D individual value articulator. Seven implants were placed using guided surgery and the prosthetic rehabilitation was successfully performed as planned. Conclusion: The use of guided surgery guarantees atraumaticity and procedure predictability as documented in recent literature. However, in this case, for the first time, using the digital axiograph and digital articulator, it was possible to record the axiography of condylar movements in order to 'functionalize' the diagnostic wax-up prior to its insertion into guided surgery software. This clinical case suggests how the software's compatibility with intra-oral scan files, diagnostic wax-up, facial scans, CBCT and, in the near future, electromyography of mastication muscles permits the clinician to work on a virtual patient and analyze all critical aesthetic and functional parameters prior to guided surgery.

Effect of decompression and online transmission on the dimensional changes of .stl files generated by intra-oral scanning.

Intraoral scans became part of the virtual planning in Dentistry. In the new scenario of digital workflows, dental clinics and laboratories had to establish an online communication that requires the compression, decompression, and transmission of 3D files. Knowledge about the effects of these procedures on the dimensional properties of the files is fundamental to ensure a more realistic virtual planning. The aim of this study was to assess the influence of 3D file compression, decompression, and online transmission on the dimensional properties of dental models from intraoral scanning. Intraoral scan files in.stl format of 50 patients were selected from the database of a dental radiology clinic, with 25 of these patients with mixed dentition and 25 with permanent dentition. The maxilla and mandible scans of each patient were included in the study, generating a total of 100 files. A folder with the 100 files was created and replicated six times with different labels (A, B, C, D, E, F), totaling a sample number of 600 files. Folder A was compressed by WinZip and then decompressed. Folder B went through the same process, but the step of compression and decompression by WinZip was repeated 10 times. The folders C, D, E, F were sent, respectively, through the platforms WeTransfer, Dropbox, Google Drive, and OneDrive, then each of them was downloaded in their respective platforms. After the six folders went through the compression process and were sent by the platforms, each file in the folder was compared with its original file by superimposing the 3D images and identifying the dimensional deviation in the compressed file in relation to the original file. We observed that there were no differences between the six groups regarding dimensional changes from the compression, decompression and online transmission processes. The lack of dimensional changes was observed for the sets of permanent and deciduous. teeth We concluded that it is possible to compress, decompress, and transfer.stl format files online without causing dimensional distortions in the 3D model.

Different implant diameters and their effect on stress distribution pattern in 2-implant mandibular overdentures: A 3D finite element analysis study

Statement of problemThe edentulous mandible is commonly treated with a 2-implant overdenture. A change in diameter of the implants may affect the biomechanical behavior of the overdenture, but information on these effects is lacking. PurposeThe purpose of this 3D finite element analysis study was to evaluate the biomechanical behavior of 2-implant mandibular overdentures (2IMO) and their individual components by using implants of different diameters. Material and methodsA 3D mandibular model was obtained from the cone beam computed tomography (CBCT) images of a 59-year-old edentulous man, and a 3D denture model was developed from intraoral scanning files in the Mimics software program. A 3D model of different diameters of implants (2.5 mm, 3.0 mm, 3.5 mm, and 4.0 mm) with a LOCATOR attachment was developed in the Solidworks software program. Two same-sized implants were inserted in the mandibular model at 10 mm from the midline in the 3Matics software program. A vertical load of 100 N was applied on the first molar region on the right side or both sides in the ANSYS software program. The maximum von Mises stresses and strains were recorded and analyzed. ResultsStresses within the implants decreased with an increase in diameter (from 2.5 mm to 3 mm, 3.5 mm, and 4.0 mm) of the implants. The highest stresses were observed with 2.5-mm-diameter implants (0.949 MPa under unilateral and 0.915 MPa under bilateral loading) and the lowest with Ø4-mm implants (0.710 MPa under unilateral and 0.703 MPa under bilateral loading). The strains on the implants ranged between 0.0000056 and 0.0000097, and those on the mandible ranged between 0.0000513 and 0.0000566 across all diameters of the implants without following a specific trend. ConclusionsIn 2IMO, the stresses in the implants and mandible decreased with an increase in the diameter of the implants. The implants of lesser diameter (2.5 mm) exhibited the highest stresses and strains, and the implants of the largest diameter (4 mm) exhibited the lowest stresses and strains under unilateral and bilateral loading conditions.

Assessment of the readiness of restorations manufactured by CAD/CAM in terms of marginal fit (Part I).

BackgroundThe master cast is the gold standard for the control and eventual adjustment of restorations produced by conventional procedures. Some digital workflow bypasses the master cast and relies completely on the precision of the CAD/CAM restoration.AimTo examine the reproducibility of the margins of CAD/CAM restorations generated from a single digital scan. Also, to check the readiness of these restorations for delivery directly after fabrication without adjustment on a master cast and thereby eliminate the need for the master cast.MethodsA total of 18 metal substructures made from cobalt chrome alloy were fabricated utilizing a single STL file. The circumference was divided into eight zones. The vertical marginal discrepancy (VMD) was measured at each zone of each metal substructure, with optical microscopy at ×200 magnification.ResultsMeasurements of vertical marginal discrepancy were in a range of (−94: 300) with a mean of 62 ± 60 μm. A one-way ANOVA test revealed that the mean VMD is significantly different among the 18 substructures (F17, 1,134 = 63.948, p < 0.001).ConclusionAlthough all the received substructures were fabricated from the same scan file, they were not identical and varied widely, and they were going outside the acceptable range in some zones. Within the limitations of this study, the marginal fit can be improved by extraoral adjustments on the master cast. Thus, skipping the master cast deprives the dentist of delivering a restoration of higher quality.

Accuracy of intraoral scanners in different complete arch scan patterns

Statement of problemThe accuracy (trueness and precision) of intraoral scanners and complete arch scans remains controversial. PurposeThe purpose of this in vitro study was to compare the trueness and precision of 3 intraoral scanners with various scan patterns. Material and methodsFour standard metal spheres were installed on a dental maxillary cast according to American National Standard/American Dental Association (ANSI/ADA) specification no. 132. Six distances among the center of spheres were measured with a coordinate measuring machine and used as references. Four different scanning patterns were assigned: zigzag, occlusal-palatal-buccal, occlusal-buccal-palatal, and molar-to-canine. Dental Wings and TRIOS 3 applied to the first 3 scan patterns, while True Definition applied to all patterns (n=30). Six distances in the scan files were also measured and calculated for relative errors of trueness and precision. A ratio less than 0.0025 was considered acceptable and used for binary outcome analysis. Differences among scanners and scan patterns in terms of trueness and precision were analyzed with the chi-squared test, Fisher exact test, and logistic regression (α=.05). ResultsThe zigzag scan pattern from TRIOS 3 and the occlusal-buccal-palatal pattern from True Definition exhibited 100% acceptable precision. TRIOS 3 revealed the highest number of acceptable trueness values in the occlusal-palatal-buccal scan (88.3%). The scan patterns from Dental Wings and TRIOS 3 were related to the trueness. TRIOS 3 and True Definition were 12.8 and 6.4 times more likely to obtain acceptable trueness than Dental Wings (P<.001). The zigzag scan pattern had the highest chance of obtaining acceptable trueness. ConclusionsThe scan patterns influenced the trueness and precision of the intraoral scanners in different ways. For the best trueness, TRIOS 3 should be applied with an occlusal-palatal-buccal scan pattern, Dental Wings should be applied with a zigzag scan pattern, while True Definition can be used with any scan pattern.

Three-dimensional (3D) Visualization Educational Modeling for Ophthalmology Residents' Training: Viewpoints.

Background: Three-dimensional models are used to guide residents and physicians in accessing specific anatomical areas and types of fractures and better diagnosis of anomalies. These models are useful for illuminating complex anatomical areas, such as orbit, especially limited space with sensitive access. The aim of this study was to design a three-dimensional visualization educational modeling for ophthalmology residents' training. Methods: This study is a product-oriented application that uses radiological images of anatomy, anomalies, and orbital fractures based on actual CT scans of patients. These CT scans were carefully selected from the Picture Archiving and Communication System of Ghaem Hospital of Mashhad University of Medical Sciences. Results: To produce twelve 3D models, the CT scan files were converted to 3D printer output. Then, the models were presented to residents at a training session by an ophthalmologist. These models created all major fractures associated with the orbit area and most disorders, anomalies of this area and several normal anatomical. The features of 3D models were mentioned. The strengths and weaknesses of the educational modeling, the level of satisfaction with the use of three-dimensional models, suggestions and criticisms were assessed qualitatively by the residents. Satisfaction was reported 100% by residents. Suggestions for future 3D models were presented, and the only criticism was fear of exams and grades. Conclusion: Real-size 3D modeling help to understand the spatial and mental imagery of anatomy and orbital pathology and to touch different anatomical areas creates a clear image in the minds of residents, especially in the orbit.

Influence of Different Fabrication Techniques on the Accuracy of Radiographic Scan Templates in Cases of Full-Arch Computer-Guided Implant Placement: An In Vitro Study.

To evaluate the influence of using different fabrication techniques, including intraoral scans, CBCT scans of patients' existing dentures, or denture duplicates, on the accuracy of radiographic scan templates. The influence of selecting different segmentation threshold values during reconstruction of CBCT data was also evaluated. A reference model was obtained by scanning five pairs of maxillary and mandibular acrylic complete dentures using a desktop laboratory laser scanner (DWOS 7Series, Dental Wings). Test scans were obtained from intraoral scans of dentures, CBCT scans of dentures and denture duplicates reconstructed at different grayscale segmentation thresholds, and a laboratory scan of denture duplicates. The resultant STL scan files were imported to an open source and cloud storage software (Medit Link) for the accuracy measurements by calculating root mean square estimate (RMSE) between reference and test scans. Collected data were then analyzed. Qualitative analysis was also performed using 3D color maps. The lowest RMSE (352.7) was found with intraoral denture scans. The highest RMSE (1,336.3) was found with the CBCT scans of the denture duplicates at segmentation threshold of -700 grayscale level. Qualitative analysis revealed that the intraoral denture scans exhibited the most homogenous deviation pattern relative to reference lab scans. Within the limitations of this study, the intraoral scans of the patients' existing dentures resulted in the fabrication of the most accurate radiographic scan templates. The improved accuracy of scan templates fabricated using the intraoral scanners can eliminate the possible laboratory errors associated with the conventional technical procedures as well as reduce the inaccuracies resulting from the image processing and segmentation of CBCT data.

Automatic Estimation of Body Measurements to Extract the Size and Body Shape

This paper presents the research results of automatic estimation of the neck girth and inside leg to extract the size and body shape from the male sizing system table. The data used in the study is the 3D scan file *.obj from the 3D body scanner. The author uses the interpolation and optimization method in the algorithm to automatically extract 2 primary dimensions combined with the fuzzy logic method to extract sizes, body shapes. Besides, rotate matrix method combines with the optimal function used to write an algorithm to estimate the neck girth, inside leg measurements. Furthermore, a simple approach based on vertices and surface normal vectors data and optimal search was adapted to estimate the neck girth and inside leg measurements. These extraction results will be linked to the algorithm of the fuzzy logic to run for the automated process. This automatic algorithm will be very useful in face-to-face clothing purchases or online or for garment manufacturers in reducing shopping time and choosing sizes to design samples for customers.

Accuracy of Different Surgical Guide Designs for Static Computer-Assisted Implant Surgery: An In Vitro Study.

The aims of this study were to evaluate the effect of (1) the different surgical guide designs and (2) implant placement location on the accuracy of fully guided implant placement in single edentulous sites using an in vitro study model. Forty-five partially edentulous models were scanned and divided into 3 groups: group 1, tooth-supported full-arch surgical guide; group 2, 3 different tooth-supported shortened surgical guides (SSGs); and group 3, tooth-supported full-arch surgical guide with a crossbar. All surgical guides were printed and used for fully guided implant placement. A total of 180 implants (60 per group) were placed, and scan bodies were positioned on all models, and postoperative surface scan files (STL) files were obtained. Superimposition of preoperative and postoperative STL files was performed, and the accuracy of implant position was evaluated. The interaction between group and implant location was statistically significant for angle, 3D offset at the base, and at the tip (P < .001). The post-hoc tests showed a statistically significantly higher deviation for group 2 compared to group 3 for all outcomes for implants #4 (P < .05) and #7 (P < .05). There was also a statistically significant difference in all outcomes between groups 1 and 3 for implant #7 (P < .05). All surgical guide designs presented satisfactory performance with clinically acceptable levels of deviation. However, SSGs presented higher accuracy for guided implant placement in a single-edentulous site, whereas a full-arch surgical guide with a crossbar presented superior outcomes when 2 or more guided implants were placed simultaneously.

Effect of print orientation on the dimensional accuracy of orthodontic aligners printed 3-dimensionally

Fabrication of orthodontic aligners directly via 3-dimensional (3D) printing presents the potential to increase the efficiency of aligner production relative to traditional workflows; however tunable aspects of the 3D-printing process might affect the dimensional fidelity of the fabricated appliances. This study aimed to investigate the effect of print orientation on the dimensional accuracy of orthodontic aligners printed directly with a 3D printer. A digitally designed aligner of 500μm thickness was printed in 3D in Grey V4 (Formlabs, Somerville, Mass) resin at 8 angulations at 45° intervals (n=10 per angulation) using a stereolithography 3D printer. Each aligner was scanned with an optical scanner, and all but the intaglio surface of each scan was digitally removed. Each resultant scan file was superimposed onto the isolated intaglio of the designed master aligner file. The dimensional deviation was quantified with Geomagic Control software (3D Systems, Rock Hill, SC), and data were analyzed using R statistical software (version 2018; R Core Team, Vienna, Austria) (P<0.05). Print angle showed a statistically significant effect on standard deviation, average positive deviation, absolute average negative deviation, and percentage of points out of bounds (tolerance bounds defined as ±250μm)(P<0.05). Qualitative analysis of the 3D surface deviation maps indicated that the 0° and 90° groups showed less deviation and appeared to be the most accurate in the anterior regions. Overall, the majority of the print angle groups studied were not printed within clinically acceptable tolerance ranges, with the major exception being the 90° group, which printed nominally within clinically acceptable tolerance ranges. With the workflow applied, print orientation significantly affects the dimensional accuracy of directly 3D-printed orthodontic aligners. Within the limitations of this study, printing at the 90° angulation would be advised as it is the group with the most accurate prints relative to the 7 other orientations investigated, although not all differences were statistically significant.

Comparison of the Accuracy of Intraoral Scanners Based on the Type of Tooth Preparation for a Single Crown

The purpose of this study was to evaluate the accuracy of intraoral scanners in 10 abutments (five premolars and five molars) obtained in a dental clinic and to analyze the impacts of the volume and area of abutments on scanning accuracy. Abutment casts were scanned five times with a 3D contact scanner (DS10; Renishaw plc). The five scan files were lined up and then merged, and one high-resolution computer-aided design reference model (CRM) was obtained. To obtain a computer-aided design test model (CTM), three types of intraoral scanners (CS3600 (Carestream Dental), i500 (Medit), and EZIS PO (DDS)) and one type of laboratory scanner (E1; 3Shape) were employed. Using 3D analysis software (Geomagic control X; 3D Systems), the accuracy of the scanners was evaluated, including optimal overlap by optimal alignment. The conformity of the overlapped data was calculated by the root mean square (RMS) value, using the 3D compare function for evaluation. As for statistical analysis, testing was conducted, using one-way and two-way ANOVA and the Tukey HSD test (α = 0.05) for the comparison of the groups. To analyze the correlations of the volume and area of the abutments with accuracy, Pearson’s correlation analysis was conducted (α = 0.00625). Both premolar and molar abutments showed a lower RMS value on the laboratory scanner than on the intraoral scanners, and the RMS value was lower in premolars than in molars (p &lt; 0.001). In the intraoral scanner group, CS3600 showed the best accuracy (p &lt; 0.001). There were significant positive correlations for the volume and area of the abutments with accuracy (p &lt; 0.001). The type, volume, and area of the clinically applicable abutments may affect the accuracy of intraoral scanners; however, the scanners used in the present study showed a clinically acceptable accuracy range, regardless of the type of abutment.

Accuracy of Different Head Movements of Intraoral Scanner in Full Arch of Both Maxilla and Mandible

This in vitro study aimed to compare the accuracy of maxilla and mandible full-arch scans from an intraoral scanner via one scan path with six different head movements. Standard maxilla and mandible models via holder were set in a dental chair to simulate position and posture. The reference models’ standard tessellation language (STL) files were formatted via desktop scanner, and operative models’ files were obtained via IOS TRIOS 3 Pod as superimposed by Exocad CAD software. The same scan path with six head movements (Linear, Circle, Wave, 8-figure, S-figure, and A-P) were designed to scan 10 times per jaw, and a total of 120 scan files were then compared with reference files. The data were recorded and deviations of both occlusal and B-L sides were compared, with statistical analysis being performed by one-way analysis of variance (ANOVA) and post hoc comparisons with Tukey test. The trueness of optical impression for full-arch via one path with six head movements differed from maxilla and mandible and depended on the different movements (p &lt; 0.05). In the same path, peak deviation was found at the turning points for left central incisor, left first premolar, left second molar, and right second molar in maxilla, and for right first premolar, second molar, and left second molar in the mandible. The 8-figure movement showed the highest deviation (0.128 ± 0.086 mm) in the maxilla and (0.105 ± 0.069 mm) in the mandible. The Linear movement presented the lowest deviation (0.096 ± 0.07 mm) in the maxilla while the Circle movement presented the lowest deviation (0.073 ± 0.041 mm) in the mandible, with the 8-figure movement showing the worst precision among six movements. In the maxilla, the S- and 8-figure movements were not recommended, while the Linear and Circle movements showed high trueness. In the mandible, the 8-figure movement was not recommended, while the other five presented similar lower deviations.

Dimensional changes of complete dentures fabricated by milled and printed techniques: An in vitro study

Statement of problemInformation on the dimensional changes in maxillary and mandibular dentures made by using computer-aided design and computer-aided manufacturing (CAD-CAM) techniques under uniform testing conditions is lacking. PurposeThe purpose of this in vitro study was to evaluate the dimensional changes and reproducibility of maxillary and mandibular dentures by using CAD-CAM-milled and 3D-printed techniques. Material and methodsMaxillary and mandibular edentulous models with wax occlusal rims were scanned, and dentures were designed by using a CAD software program and fabricated by using 2 techniques and materials: CAD-CAM-milled (CCM) and 3D-printed (3DP). The 3DP fabrications included 4 subgroups: dentures printed with a 90-degree build angle with UV light polymerization on the reference model (3DP 90M), dentures printed with a 90-degree build angle and light polymerization without the reference model (3DP 90), dentures printed with a 45-degree build angle with light polymerization on the reference model (3DP 45M), and dentures printed with a 45-degree build angle and light polymerization without the reference model (3DP 45). The preprocessing and postprocessing scan files of each denture produced by CCM and 3DP were superimposed by using a surface matching software program. Ten points each on maxillary and mandibular dentures were measured for deviations after processing. Additionally, for each denture, the widths were measured between the canines and molars, the anteroposterior plane from cusp tips between the canines and molars, and the vertical plane from the cusp tip of the canines to the marginal gingiva. They were then compared with those in the denture design CAD cast. The Kruskal-Wallis analysis of variance test was used for statistical analyses (α=.05). ResultsAccording to digital superimposition, CCM had the smallest values of deviation with no statistical difference (P>.05), indicating more uniform results from measurement points in both maxillary and mandibular dentures, followed by 3DP 90M, 3DP 90, 3DP 45M, and 3DP 45. Regarding the width measurements, CCM had the smallest values of deviation (P<.05). In 3DP, smaller deviation values were observed at the vertical plane from the tip of the canine to the marginal gingiva, and larger values were observed in the intermolar width (P<.05). ConclusionsCCM exhibited smaller dimensional changes and better reproducibility among the tested techniques. In 3DP, the build angle and methods of light postprocessing influenced the dimensional stability. The 90-degree build angle with additional light polymerization on the cast improved the dimensional deviations.

Load bearing analysis on Lumbosacral Disc in Pre-operative and Post-operative Thoracic Scoliosis Patient

Scoliosis is a musculoskeletal disorder seen all around the world. It affects both the alignment of the vertebra and intervertebral disc. Scoliosis can be treated conservatively with a cast and brace or surgically with spinal instrumentation. During planning for surgical instrumentation, several factors need to be considered. Among those, biomechanical changes in the non-scoliotic vertebrae and discs are important. This is vital in determining the future degenerative changes of the spine. For this reason, this study was conducted with a finite element model of the lumbosacral joint using CT scan files to find the total deformation and equivalent static strain of the lumbosacral disc between pre and post-operative thoracic scoliosis patient. From the results, it is evident that there is a biomechanical change in the lumbosacral disc and structural change in the vertebral alignment followed immediately after corrective surgery. The correction in the alignment of the scoliotic spine brings changes to the biomechanical functionality and load-bearing capacity of the lumbosacral intervertebral disc before and after surgery.

Digital and analog vertical dimension measurements: A clinical observational study.

To compare the rest vertical dimension (RVD) and occlusal vertical dimension (OVD) measurements obtained using a facial scanner with conventional methods and to evaluate the influence of the file format on the accuracy of the digital calculations. Participants (N = 30) received marks on the glabella (Gb), tip of the nose (TN), and pogonion (Pg). Interlandmark distances Gb-TN and TN-Pg in the OVD and RVD positions were recorded by two operators conventionally (manual group) and digitally (digital group). For the manual group, measurements were obtained using a caliper. For the digital group, 10 scans in each position were obtained using a facial scanner (Face Camera Pro, Bellus3D) and exported in tessellation with polygonal faces (OBJ) and standard tessellation language (STL) file formats. Digital measurements were performed using both facial scan file formats and a software (Matera 2.4, exocad). The interocclusal rest distance (IRD) and the intraclass correlation coefficient were calculated. Shapiro-Wilk test was used to determine normal distribution. An independent samples t test, one-way analysis of variance, and post hoc Tukey test were used for analyses (± = .05). No significant differences were found between the manual and digital measurements using the OBJ files or digital measurements using the STL files (P > .05). The IRD ranged from 0.72 ± 0.48 mm to 5.00 ± 1.34 mm. The inter- and intra-operator reliability were significant (P < .001), with a Cronbach's alpha value ranging from .994 to .997. No difference was found between manual and digital measurements. A high measurement consistency was encountered for each operator and between the operators. The facial scan file format did not influence the digital measurements.