Stereolithography File Research Articles

Comparative evaluation of internal and marginal fit of interim crowns fabricated by CAD/CAM milling and two different 3D printing systems - An in vitro study

The aim of the present study is to compare and evaluate the internal and marginal fit of interim crowns fabricated by CAD/CAM milling and two different 3D printing systems. Fabrication of the metal master model was done by Selective Laser Melting Unit after preparing and scanning a typhodont tooth. A designing software was used to design crowns onto the metal master model after scanning it. The STL (Stereolithography) file of designed crowns is then sent to CAD/CAM milling machine and two different 3D printing systems namely Stereolithography (SLA) and digital light processing (DLP) for fabrication of 15 crowns each. Internal and marginal fit was measured with the help of silicon replica technique and obtained data was analysed with one way ANOVA which was followed by Tukey’s post-hoc analysis test for verifying the statistical significance. The smallest discrepancy of 96.7 μm was observed in DLP 3D Printing group followed by 131.1 μm in SLA 3D printing group and lastly CAD/CAM group stood with the discrepancy of 179.6 μm. A significant difference was seen for discrepancy values of the 3 groups and it was observed that DLP 3D Printing was able to manufacture crowns with better marginal and internal fit than SLA 3D Printing and SLA 3D Printing was better than CAD/CAM Milling group.

Development of a framework for computer aided design and manufacturing of 3 axis hybrid wire arc additive manufacturing

Hybrid Wire Arc Additive Manufacturing (H-WAAM) has revolutionized modern metal manufacturing industries through its ability to realize medium to large metallic components within a short span of time. In H-WAAM, Computer-Aided Process Planning (CAPP) is the basic step that helps in improving the productivity and quality of the fabricated components. CAPP of H-WAAM needs to be treated differently from that of traditional AM due to the higher deposition rate and synergistic involvement of the subtractive process. The traditional CAPP solutions used for AM are restricted to Stereolithography (STL) file format and provide limited access to the process parameters. However, if a CAD/CAM system that has been dedicatedly developed for the SM satisfies certain conditions then it can be utilized for the CAPP of H-WAAM. Therefore, in this work, a generalized framework for utilizing any CAD/CAM system for the CAPP of the H-WAAM has been proposed. The framework supports a wide variety of standard CAD formats and enables the user to choose several build strategies. The toolpath for deposition as well as machining can be generated with a common work coordinate system. This eliminates the time it takes to move components from one platform to another. The developed framework has been validated through a case study of fabricating an impeller.

Ex vivo digital comparison of four impression techniques using an industrial laser scanner

Introduction: The aim of the study was to compare different impression techniques used for fixed prosthodontics. Methodology: A master cast with prepared abutments was created from polymethyl-methacrylate (PMMA). A high-resolution industrial scanner was used to create a virtual reference model. Four different impressions were made, three with polyvinyl-siloxane (PVS) (n = 10 for each): one-step putty-wash (1SPW), two-step putty-wash prepared with an escape channel (2SPW-Ch), two-step putty-wash with a polyethylene spacer foil (2SPW-Fo), and one with polyether monophasic technique (MP) from the PMMA model and digitized with an industrial scanner. The stereolithographic (STL) files of the impressions (n = 40) were exported. Each file was compared to the reference using the Geomagic Verify software. Six points were assigned to enable virtual calliper measurement of tooth diameters and distances of varying sizes within the arch. Results: In the case of die diameters, the deviation from the mould ranged from 31.84 to 180.64 μm. At the stump diameter level, the MP and 1SPW techniques showed significantly more minor differences than the 2SPW-Ch, and the MP was significantly more accurate than the 2SPW-Fo. At medium distance, the deviation ranged from 42.74 to 136.47 μm. Therefore, MP was found to be significantly more accurate than 2SPW-Ch. When examining the long distance, the difference was between 162.62 and 348.85 μm. The MP and 1SPW impression techniques proved significantly more accurate than the 2SPW-Ch technique for long distances. Conclusions: With both simultaneous techniques, significantly more true results were achieved than with the two-step techniques. Keywords: Dental Impression Technique; Scanning of the Impression; Monophase; One-Step Putty-Wash; Two-Step Putty-Wash.

Ex vivo digital comparison of four impression techniques using an industrial laser scanner

Introduction The aim of the study was to compare different impression techniques used for fixed prosthodontics. Methodology A master cast with prepared abutments was created from polymethyl-methacrylate (PMMA). A high-resolution industrial scanner was used to create a virtual reference model. Four different impressions were made, three with polyvinyl-siloxane (PVS) (n = 10 for each): one-step putty-wash (1SPW), two-step putty-wash prepared with an escape channel (2SPW-Ch), two-step putty-wash with a polyethylene spacer foil (2SPW-Fo), and one with polyether monophasic technique (MP) from the PMMA model and digitized with an industrial scanner. The stereolithographic (STL) files of the impressions (n = 40) were exported. Each file was compared to the reference using the Geomagic Verify software. Six points were assigned to enable virtual calliper measurement of tooth diameters and distances of varying sizes within the arch. Results In the case of die diameters, the deviation from the mould ranged from 31.84 to 180.64 µm. At the stump diameter level, the MP and 1SPW techniques showed significantly more minor differences than the 2SPW-Ch, and the MP was significantly more accurate than the 2SPW-Fo. At medium distance, the deviation ranged from 42.74 to 136.47 µm. Therefore, MP was found to be significantly more accurate than 2SPW-Ch. When examining the long distance, the difference was between 162.62 and 348.85 µm. The MP and 1SPW impression techniques proved significantly more accurate than the 2SPW-Ch technique for long distances. Conclusions With both simultaneous techniques, significantly more true results were achieved than with the two-step techniques.

Comparative evaluation of stress distribution of zirconia, cobalt chromium, and polyetheretherketone (PEEK) framework material on an atrophic maxilla in all-on-six implant treatment concepts: A three-dimensional finite element analysis

Aims: This study aims to evaluate the effect of prosthetic framework material on the stress distribution patterns of the all-on-six implant support system under vertical and oblique loading. Materials and methods: The cone beam computed tomography (CBCT) images of the maxilla were converted to a stereo lithography file. HyperMesh software system was accustomed to convert three-dimensional pictures into numerical models. Geometric models of short implant and zirconia, cobalt chromium, and polyetheretherketone (PEEK) framework material were created using SOLID EDGE software and were then inserted in the bone model. A total of six models were constructed with three different types of framework materials with four implants in the anterior maxilla region and two distal short implants and mini-abutments. The prosthetic frameworks were made with 14 teeth (central incisors to the second molar bilaterally). The models were transferred through the solid works simulation program for finite element analysis and stress distribution investigation. An oblique load of 150 N with 30 inclination in the linguo-buccal direction and vertical loads parallel to the long axis of the tooth with 100 N magnitude were applied unilaterally on the posterior teeth of each framework. Results: Principal and Von misses stress in the PEEK framework were least when compared to stresses in the zirconia and cobalt chromium framework on vertical loading and oblique loading. Conclusion: PEEK as a framework material had the least stress for the all-on-six implant treatment concepts on vertical and oblique forces than zirconia and cobalt chromium framework.

Computer-Guided Bone Biopsy: A Technical Note with the Description of a Clinical Case.

Aim: The aim of this technical note is to present a computer-aided design–computer-aided manufacturing (CAD–CAM) surgical guide to perform a computer-guided bone biopsy. Traditionally, to diagnose abnormal conditions affecting jawbone, a bone biopsy is performed with the use of a trephine bur. The positioning of the bur, during the biopsy, is based on the skill of the surgeon; therefore, an inaccurate placement of a trephine bur may occur. The use of a guide, however, can minimize this risk and achieve a better result. Materials and Methods: To determine the site and the extension of bone sampling, the stereolithography file (STL) file of cone–beam computed tomography (CBCT) images is acquired using a specific planning software and superimposed with the STL file of a dental cast; a virtual surgical guide is designed, using the same software that allows a 3D (three-dimensional) view of the guide from different perspectives and planes. The number and site of guide tubes are determined on the basis of the width and the extension of the sampling; thanks to a 3D printer, the surgical guide is manufactured. Results: The use of a customized surgical guide realized with CAD–CAM technology allows a precise and minimally invasive approach, with an accurate three-dimensional localization of the biopsy site. Conclusions: The high precision, great predictability, time-effectiveness and versatility of the present guide should encourage the clinician to use this minimally invasive surgical approach, but controlled clinical trials should be conducted to evaluate the advantages as well as any possible complications.

Node generation in complex 3D domains for heat conduction problems solved by RBF-FD meshless method

A novel algorithm is presented and employed for the fast generation of meshless node distributions over arbitrary 3D domains defined by using the stereolithography (STL) file format. The algorithm is based on the node-repel approach where nodes move according to the mutual repulsion of the neighboring nodes. The iterative node-repel approach is coupled with an octree-based technique for the efficient projection of the nodes on the external surface in order to constrain the node distribution inside the domain. Several tests are carried out on three different mechanical components of practical engineering interest and characterized by complexity of their geometry. The generated node distributions are then employed to solve a steady-state heat conduction test problem by using the Radial Basis Function-generated Finite Differences (RBF-FD) meshless method. Excellent results are obtained in terms of both quality of the generated node distributions and accuracy of the numerical solutions.

Accuracy, time efficiency and operator preference in edentulous arch scanning: a preliminary report: a preliminary report

Aim The present in vitro study evaluated the accuracy of intraoral scanners (IOS) in a completely edentulous arches and analyzed the influence of operator experience on accuracy, also time efficiency and operator’s difficulty perception related to IOS procedures. Materials and methods Twenty participants were enrolled for the digital scanning procedure of a maxillary edentulous metal model using an intraoral scanner, Aadva iOS100 (GC Corp., Tokyo, Japan). Participants were divided in two groups according to their experience in intraoral scanning procedures: Inexpert (InE group) without any experience in dental scanning (n=10) and Experts (E group) composed of operators with at least 3 year of scanning experience with IOS (n=5). Five IOS procedures were repeated for each operator and exported as a correspondent Stereolithography (STL) file. The same model was scanned with a laboratory scanner (LSS) (D1000 3 Shape Copenaghen Denmark), obtaining an STL file of the model which has been used as a reference. Accuracy of IOS were evaluated using a surface adaptation software (Geomagic Design X). The time required for each scanning procedure, and the perceived difficulty level were recorded for all the participants. The data obtained about accuracy, scanning time and difficulty perceived were compared between the two groups using the T-test for independent samples. The same variables were also correlated with each other using the Pearson’s coefficient. Results The highest trueness was observed for the scans provided by E participants. Precision ranged from 95,89 to 79,36 respectively in E and InE operators. For both trueness and precision there were significant differences between the two groups (p<0.05). Regarding scanning time, the more experienced operators were faster than inexpert ones with a significant difference (p<0.001). The two groups reported also differences in terms of difficulty perceived. Pearson’s correlation reported for time scanning a significant correlation with trueness p<0.001 and precision p<0.05 and between difficulty perceived and trueness p<0.05. Conclusions Digital impressions accuracy was different in E and InE operators as well as the scanning times, that was correlated with both trueness and precision.

Evaluation of current additive manufacturing systems for orthodontic 3-dimensional printing

The objective of this research was to evaluate and compare linear and surface accuracy of dental models fabricated using 3 different vat photopolymerization printing units: digital light synthesis (M2Printer; Carbon, Redwood City, Calif), digital light processing (Juell 3D Flash OC; Park Dental Research, New York, NY), and stereolithography apparatus (Form 2; Formlabs Inc, Somerville, Mass), and a material jetting printing unit: PolyJet (Objet Eden 260VS; Stratasys, Eden Prairie, Minn). Maxillary and mandibular dental arches of 20 patients with the American Board of Orthodontics Discrepancy Index scores ranging between 10 and 30 were scanned using an intraoral scanner. Stereolithographic files of each patient were printed via the 3-dimensional (3D) printers and were digitized again using a 3D desktop scanner to enable comparisons with the original scan data. One-sample t test and linear regression analyses were performed. To further graphically examine the accuracy between the different methods, Bland-Altman plots were computed. The level of significance was set at P<0.05. Bland-Altman analysis showed no fixed bias of one approach vs the other, and random errors were detected in all linear accuracy comparisons. When a 0.25mm tolerance level was deemed acceptable for any positive or negative surface changes, only the models manufactured from digital light processing and PolyJet units showed more than 97% match with the original scans. The surface area of 3D printed models did not yield an utterly identical match to the original scan data and was affected by the type of printer. The clinical relevance of the differences observed on the 3D printed dental model surfaces requires application-specific judgments.

Clinical expression of programmed rotation and uprighting of bilateral winged maxillary central incisors with the Invisalign appliance: A retrospective study

Winged maxillarycentral incisors (WMCI), defined as mesiopalatal rotation of the crowns of maxillary central incisors, is a common dental trait that affects smile esthetics. This retrospective study aimed to determine the efficacy of rotation and uprighting tooth movements of bilateral WMCI with Invisalign (Align Technology, Santa Clara, Calif). Initial, predicted, and achieved stereolithography files of 30 adult patients, consecutively treated with the Invisalign SmartTrack appliance, were superimposed using Geomagic Control X 64 (3D Systems, Rock Hill, SC). The pairs of incisors were assessed for rotation using the interlabial angle (ILA), and individual incisors were measured for rotation and tip. Programmed rotation and uprighting of WMCI are mostly undercorrected with the Invisalign appliance. The mean shortfall in ILA was 10.5° (standard deviation [SD], 10.66; 95% confidence interval [CI], 5.89-14.19; P<0.001) for a mean predicted change of 35.27°. For individual incisors, a mean shortfall of 5.38° (SD, 5.88; 95% CI, 3.58-6.76; P<0.001) was found for a mean 18.75° predicted change in rotation. A mean predicted change in tip of 7.06° showed a mean shortfall of was 2.16° (SD, 3.86°; 95% CI, 1.03-3.01; P<0.001). A moderate and statistically significant correlation between shortfalls in rotation and tip was observed (r=0.44). Linear regression analysis was used to formulate an equation as a clinical tool to determine the likely achieved outcome on the basis of the predicted change. Predicted changes in rotation, ILA, and tip were both under and overexpressed. In particular, tip was dependent on the magnitude of planned change. The random inconsistencies in the clinical expression of rotation and tipping warrant careful monitoring and/or remedial actions such as overcorrections aligners.

The Influence of Laboratory Scanner Versus Intra-Oral Scanner on Determining the Implant Axis by Using Three Different Scan Abutments

Background: The purpose of this in vitro study was to compare the implant axis’ spatial position and orientation by using laboratory scanner versus intra-oral scanner with three different scan abutments. Methods: A 3D model was printed with an internal hex implant analog in the place of teeth 35#. Three standard scan abutments were used: MIS (two-piece titanium), AB (two-piece PEEK and titanium base) and ZZ (one-piece PEEK). Each scan abutment was scanned 30 times by TRIOS E3 (laboratory scanner) and 30 times by Omnicam (intra-oral scanner). For each scan, an STL (stereolithography) file was created, and the spatial characterization of each scan abutment was measured in the X, Y, Z coordinates, and rotational and longitudinal angles. The comparison between all the scans was conducted by superimposition of the STL files, using a 3D software. A t-test and Wilcoxon signed-rank test were used. (p &lt; 0.05) Results: Only the MIS scan abutment showed no statistical difference in the X and Z axes. (p &lt; 0.05). All other scan abutments showed a statistical difference in all axes. The rotational angle of the AB scan abutment was twice the angle of the MIS and ZZ scan abutments. Conclusions: All three scan abutments showed a rotational deviation of the implant axis between the laboratory scanner and the intra-oral scanner. The AB scan abutment showed the greatest deviation (1.04 degrees) while the other two abutments showed deviations of about half a degree in relation to the laboratory scan abutment. There is a need for further studies which will examine the influence of geometry, material, and scan abutment parts on the accuracy of the scan obtained.

Design and Fabrication of 3-DOF Robot Arm Using Parallelogram Mechanisms

This paper focuses on the design, fabrication and control of a 3-DOF robot arm using stepper motors. The robot arm uses three parallelogram mechanisms to position the end-effector of the robot and keep the end-effector always parallel to the horizontal during the robot motion. The robot is designed on the Autodesk Inventor software. Separated parts of the robot are saved in the stereolithography (STL) file format. Then the parts are fabricated by a 3D printer. The movement of the robotic arm is driven by stepper motors and controlled by Arduino. The Arduino board implements kinematics calculation, creates pulses and sends them to three drivers to driven stepper motors. A software is developed to control the robot by sending the command to the Arduino board.

A novel workflow for indirect cobalt-chromium restorations using additive manufacturing without digital design.

This preliminary investigation explored additive manufacturing to fabricate cobalt-chromium onlay restorations without the use of digital design. Extracted molars were prepared for four-surface onlays followed by the conventional approach for the fabrication of provisionals. The provisionals were digitized with an intraoral scanner, and stereolithography (STL) files were fabricated with additive manufacturing in cobalt-chromium, utilizing selective laser melting (SLM). Onlays were bonded to the corresponding tooth. Restorations were polished after cementation and assessed with photography, radiography, and a clinical post-cementation checklist. Cementation was unremarkable; marginal adaption and surface finish were generally acceptable. A simple, efficient, and inexpensive alternative workflow for the fabrication of indirect restorations without using the digital design is proposed.

Predictability of overbite control with the Invisalign appliance

Control of overbite is considered essential in achieving ideal orthodontic outcomes. Questions have been raised regarding the accuracy of ClinCheck software (AlignTechnology, Santa Clara, Calif) in predicting posttreatment outcomes with Invisalign, with the paucity of well-researched literature available on this topic. This research aimed to investigate and determine the accuracy of Invisalign (Align Technology) in correcting a deep overbite by comparing the outcomes predicted by ClinCheck with achieved posttreatment outcomes. A retrospective study was conducted using pretreatment and posttreatment intraoral scans and predicted outcome (ClinCheck) stereolithography files of 42 adult patients consecutively treated with Invisalign from January 2014 and completed before July 2018, selected from the files of 1 experienced orthodontist. Patients included in the study were treated without extractions and with a minimum of 14 dual arch Invisalign aligners using a 2-weekly aligner change protocol. The pretreatment, posttreatment, and predicted outcome stereolithography files for each patient were imported into Geomagic Control X (3D Systems, Rock Hill, SC) software to measure overbite. The deeper the patient's initial overbite and the greater the amount of programmed reduction in overbite according to ClinCheck, the greater the discrepancy in overbite expression posttreatment. ClinCheck over-predicted overbite reduction in 95.3% of patients in which, on average, only 39.2% of the prescribed overbite reduction was expressed. Overbite reduction may result in suboptimal outcomes when using the Invisalign appliance unless remedial measures are employed. The deeper the initial overbite, the more challenging it is to achieve the prescribed posttreatment overbite.

3D Printed Chitosan Composite Scaffold for Chondrocytes Differentiation.

Our aim is to develop 3D printed chitosan-gelatin-alginate scaffolds using a costeffective in house designed 3D printer followed by its characterization. To observe chondrocyte differentiation on 3D printed scaffolds as part of scaffold application. Cartilage is considered to be a significant tissue in humans. It is present in between the rib cage, the lobe of the ear, nasal septum in the form of hyaline cartilage, in between ribs costal cartilage, intervertebral discs in the form of fibrocartilage, meniscus, larynx, epiglottis and between various joints of bones. To replace or repair damaged tissues due to disorders or trauma, thousands of surgical procedures are performed daily. 3D printing plays a crucial role in the development of controlled porous architectures of scaffolds for cartilage tissue regeneration. Advancement in 3D printing technology like inkjet, micro- extrusion in 3D bioprinting, Laser-assisted 3D Bioprinting (LAB), stereolithography combination with biomaterials plays a crucial role in the quick development of patient-specific articulating cartilage when need in a short period frame. Our objective is to develop different compositions of chitosan-gelatin-alginate composite hydrogel scaffolds with controlled porosity and architectures with the application of 3D printing and observe the growth of cartilage on it. To achieve as proposed, an in-house 3D paste extruder printer was developed, which is capable of printing porous composite chitosan hydrogel scaffolds of desired architecture layer by layer. After the characterization of 3D printed chitosan composite scaffolds, the differentiation of chondrocyte was observed using hMSC. In present paper process for the development of chitosan-alginate-gelatin composite hydrogel, 3D printing, morphological characterization, and observation for differentiation of chondrocytes cells on 3D printed chitosan composite hydrogels is presented. The present study is divided into three parts: in first part development of composite chitosan-alginate-gelatin hydrogel with the utilization of in house customized assembled paste extruder based 3D printer, which is capable of printing chitosan composite hydrogels. In the second part, the characterization of 3D printed chitosan composite scaffolds hydrogel is performed for evaluating the morphological, mechanical, and physical properties. The prepared composite scaffolds were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction(XRD), Scanning Electron Microscopy SEM, swelling property, mechanical testing, porosity, etc. In the last part of the study, the differentiation of chondrocytes cells was observed with human Mesenchymal Stem Cells (hMSC) on 3D printed scaffolds and showed positive results for the same. Stereolithography (STL) files of 3D models for porous chitosan composite were developed using Computer-Aided Design (CAD) and printed with a hydrogel flow rate within the range of 0.2-0.25 ml/min. The prepared scaffolds are highly porous, having optimum porosity, optimal mechanical strength to sustain the cartilage formation. The 3D printed chitosan composite scaffolds show supports for the differentiation of chondrocytes. The above study is helpful for in-vivo regeneration of cartilage for patients having related cartilage disorders. This method helps in regeneration of degenerated cartilage for patient-specific and form above experiment we also concluded that 3D printed chitosan scaffold is best suited for the regeneration of chondrocyte cells.

Slicing Algorithm and Partition Scanning Strategy for 3D Printing Based on GPU Parallel Computing.

Aiming at the problems of over stacking, warping deformation and rapid adjustment of layer thickness in electron beam additive manufacturing, the 3D printing slicing algorithm and partition scanning strategy for numerical control systems are studied. The GPU (graphics processing unit) is used to slice the 3D model, and the STL (stereolithography) file is calculated in parallel according to the normal vector and the vertex coordinates. The voxel information of the specified layer is dynamically obtained by adjusting the projection matrix to the slice height. The MS (marching squares) algorithm is used to extract the coordinate sequence of the binary image, and the ordered contour coordinates are output. In order to avoid shaking of the electron gun when the numerical control system is forming the microsegment straight line, and reduce metal overcrowding in the continuous curve C0, the NURBS (non-uniform rational b-splines) basis function is used to perform curve interpolation on the contour data. Aiming at the deformation problem of large block components in the forming process, a hexagonal partition and parallel line variable angle scanning technology is adopted, and an effective temperature and deformation control strategy is formed according to the European-distance planning scan order of each partition. The results show that the NURBS segmentation fits closer to the original polysurface cut line, and the error is reduced by 34.2% compared with the STL file slice data. As the number of triangular patches increases, the algorithm exhibits higher efficiency, STL files with 1,483,132 facets can be cut into 4488 layers in 89 s. The slicing algorithm involved in this research can be used as a general data processing algorithm for additive manufacturing technology to reduce the waiting time of the contour extraction process. Combined with the partition strategy, it can provide new ideas for the dynamic adjustment of layer thickness and deformation control in the forming process of large parts.

An algorithm for trajectory planning of complex surface parts for laser cladding remanufacturing

This paper aims to solve the problem of laser cladding for complex parts, a trajectory planning method for complex parts is proposed. First, the part model is transformed into stereolithography (STL) files, the plane groups are established where the spacing of plane groups is determined by the overlap ratio, and the direction is perpendicular to the laser scanning. Further, to obtain the excellent cladding performance, a search algorithm based on the height error of adjacent cladding is proposed to select effective points. After this, adjacent points are clustered to a dataset according to the relative position that decided by the angle. Meanwhile, the position and the attitude of all points are calculated by the geometrical characteristics and then stored. The cooperate work of positioner and robot is adopted, the attitude of the current point is adjusted using the positioner, that is, the molten pool of the current point is in a horizontal state, which can ensure the forming accuracy of curved parts after cladding. Finally, the cladding experiment of curved surface parts is carried out. The results of the analysis showed that the coating had a smooth surface and a compact structure without defects. This method can be applied in other curved parts.

Single-center experience with routine clinical use of 3D technologies in surgical planning for pediatric patients with complex congenital heart disease.

This study was planned to assess the application of three-dimensional (3D) cardiac modeling in preoperative evaluation for complex congenital heart surgeries. From July 2015 to September 2019, 18 children diagnosed with complex congenital heart diseases (CHDs) were enrolled in this study (double outlet right ventricle in nine patients, complex types of transposition of the great arteries in six patients, congenitally corrected transposition of the great arteries in two patients, and univentricular heart in one patient). The patients' age ranged from 7 months to 19 years (median age, 14 months). Before the operation, 3D patient-specific cardiac models were created based on computed tomography (CT) data. Using each patient's data, a virtual computer model (3D mesh) and stereolithographic (SLA) file that would be printed as a 3D model were generated. These 3D cardiac models were used to gather additional data about cardiac anatomy for presurgical decision-making. All 18 patients successfully underwent surgeries, and there were no mortalities. The 3D patient-specific cardiac models led to a change from the initial surgical plans in 6 of 18 cases (33%), and biventricular repair was considered feasible. Moreover, the models helped to modify the planned biventricular repair in five cases, for left ventricular outflow tract obstruction removal and ventricular septal defect enlargement. 3D cardiac models enable pediatric cardiologists to better understand the spatial relationships between the ventricular septal defect and great vessels, and they help surgeons identify risk structures more clearly for detailed planning of surgery. There was a strong correlation between the models of the patients and the anatomy encountered during the operation. 3D cardiac models accurately reveal the patient's anatomy in detail and are therefore beneficial for planning surgery in patients with complex intracardiac anatomy.

The Accuracy of 3D Printed Carpal Bones Generated from Cadaveric Specimens.

Computer assisted three-dimensional (3D) printing of anatomic models using advanced imaging has wide applications within orthopaedics. The purpose of this study is to evaluate the 3D printing accuracy of carpal bones. Seven cadaveric wrists underwent CT scanning, after which select carpal bones (scaphoid, capitate, lunate, and trapezium) were dissected in toto. Dimensions including length, circumference, and volume were measured directly from the cadaver bones. The CT images were converted into 3D printable stereolithography (STL) files. The STL files were converted into solid prints using a commercially available 3D printer. The 3D printed models' dimensions were measured and compared to those of the cadaver bones. A paired t-test was performed to determine if a statistically significant difference existed between the mean measurements of the cadavers and 3D printed models. The intraclass correlation coefficients (ICC) between the two groups were calculated to measure the degree of agreement. On average, the length and circumference of the 3D printed models were within 2.3 mm and 2.2 mm, respectively, of the cadaveric bones. There was a larger discrepancy in the volume measured, which on average was within 0.65 cc (15.9%) of the cadaveric bones. These differences were not statistically significant (P > 0.05). There was strong agreement between all measurements except the capitate's length and lunate's volume. 3D printing can add value to patient care and improve outcomes. This study demonstrates that 3D printing can both accurately and reproducibly fabricate boney models that closely resemble the corresponding cadaveric anatomy.

Efficacy of Invisalign attachments: A retrospective study

<h3>Introduction</h3> The purpose of this study was to compare the efficacy of Invisalign's (Align Technology, Santa Clara, Calif) optimized and conventional attachments on rotational and extrusive tooth movements. <h3>Methods</h3> Initial, predicted, and achieved digital dental models from 100 orthodontic patients were exported from Invisalign's ClinCheck software as stereolithography files and subsequently imported into the Slicer CMF program (version 4.7.0; http://www.slicer.org) for superimpositions on posterior teeth with no planned movement. Rotational and extrusive measurements for both optimized and conventional attachments were made on 382 teeth from the superimposition of the initial and predicted models (predicted movement) and from the superimposed initial and achieved models (achieved movement). Predicted and achieved movements were compared along with movements of teeth with optimized and conventional attachments. <h3>Results</h3> Differences between accuracies of tooth movements using optimized vs conventional attachments for both rotation and extrusion were neither statistically nor clinically significant. Mean predicted values were larger than mean achieved values for all attachment types and movements (<i>P</i> < 0.0001). For extrusion, the mean difference between predicted and achieved movements was clinically significant (0.40 mm and 0.62 mm for optimized and conventional attachments, respectively). Overall, the mean accuracy was 57.2%. Mean accuracy was 63.2% for rotation and 47.6% for extrusion. Interproximal reduction or spacing did not significantly affect accuracy. <h3>Conclusions</h3> Conventional attachment types may be just as effective as Invisalign's proprietary optimized attachments for rotations of canines and premolars and extrusion of incisors and canines. Clinicians should consider overcorrecting tooth movements, especially anterior tooth extrusion.