Standard Triangle Language Research Articles

Presurgical Virtual Planning and Intraoperative Navigation with 3D-Preformed Mesh: A New Protocol for Primary Orbital Fracture Reconstruction.

This pilot study aims to evaluate the feasibility and effectiveness of computer-assisted surgery protocol with 3D-preformed orbital titanium mesh (3D-POTM), using presurgical virtual planning and intraoperative navigation in primary inferomedial orbital fracture reconstruction. Between March 2021 and March 2023, perioperative data of patients undergoing surgery for unilateral inferomedial orbital fracture treated with 3D-POTM were analyzed. Presurgical virtual planning with a Standard Triangle Language file of preformed mesh was conducted using the mirrored unaffected contralateral side as a reference, and intraoperative navigation was used. The reconstruction accuracy was determined by: correspondence between postoperative reconstruction mesh position with presurgical virtual planning and difference among the reconstructed and the unaffected orbital volume. Pre- and postoperative diplopia and enophthalmos were assessed. Twenty-six patients were included. Isolated orbital floor fracture was reported in 14 (53.8%) patients, meanwhile medial wall and floor one in 12 (46.1%) cases. The mean difference between final plate position and ideal digital plan was 0.692 mm (95% CI: 0.601-0.783). The mean volume difference between reconstructed and unaffected orbit was 1.02 mL (95% CI: 0.451-1.589). Preoperative diplopia was settled out in all cases and enophthalmos in 19 (76.2%) of 21 patients. The proposed protocol is an adaptable and reliable workflow for the early treatment of inferomedial orbital fractures. It enables precise preoperative planning and intraoperative procedures, mitigating pitfalls and complications, and delivering excellent reconstruction, all while maintaining reasonable costs and commitment times.

Quantitative analysis of change in bone volume 5 years after sinus floor elevation using plate-shaped bone substitutes: a prospective observational study

PurposeTricalcium phosphate (TCP) has osteoconductive ability and reportedly offers similar clinical results as autogenous bone grafts in dental implant treatment. However, few reports quantify temporal changes in augmented bone volume after sinus augmentation. We aimed to establish a three-dimensional (3D) quantification method to assess bone volume after sinus augmentation and to evaluate biocompatibility of the TCP plate.MethodsMaxillary sinus floor augmentation was performed employing the lateral window technique, and plate-shaped β-TCP (TCP plate) was used instead of granular bone grafting materials. After lifting the sinus membrane, the TCP plate was inserted and supported by dental implants or micro-screws. The changes in bone volumes in the maxillary sinus before and after surgery were recorded using cone-beam computed tomography, saved as Digital Imaging and Communications in Medicine-formatted files, and transformed to Standard Triangle Language (STL)-formatted files. Pre- and post-operative STL data of bone volume were superimposed, and the augmented bone volume was calculated. Moreover, changes in bone volumes, TCP plate resorption rates, and bone heights surrounding the implants were three dimensionally quantified.ResultsFifteen implants in nine subjects were included in this study. TCP plates secured long-term space making, with results similar to those of granular bone substitutes. Newly formed bone was identified around the implant without bone graft material. TCP plate was absorbed and gradually disappeared.ConclusionsA novel 3D quantification method was established to evaluate changes in bone volume. Clinical application of TCP plate in sinus augmentation could be a better procedure in terms of prognosis and safety.

Applications and prospects of machine learning for aerosol jet printing: A review

Aerosol Jet Printing (AJP) is an additive manufacturing process that deposits ink-like materials suspended as an aerosol mist. AJP creates three-dimensional (3D) functional structures onto flat or conformal surfaces in complex shapes without the aid of additional tooling, enabling the manufacturing of extremely fine electrical interconnects with freeform structures. Due to the novelty and complexity of AJP, physical understanding is rather limited, hindering physics-based process modeling and analysis. Fortunately, the data resources from AJP applications, e.g., 3D Computer-Aided-Design data, Standard Triangle Language files, in-situ images of part, and nozzle motion records, provide an unparalleled opportunity for developing data-driven, Machine Learning (ML) methods to characterize AJP processes, support process control, and facilitate product improvement. To thoroughly identify the newfound opportunities, this study reviews state-of-the-art ML methods used in AJP applications, investigates open issues in AJP, and outlooks future development of ML-based research topics for AJP. It sheds light on how to maximize the value of ML on AJP data to develop scalable, generalizable decision-making methods. More future works along the direction will be motivated.

The Use of a 3D Image Comparison Program for Dental Identification

Dental identification involves compiling a prescribed dental chart of a deceased person’s oral findings which is then compared with antemortem dental information. However, this process is complicated, and a comparison can be difficult. In this study, the authors evaluated whether it is possible to identify images from antemortem dental information images using an image comparison program (AKAZE) with one-sided cross-sectional images generated from the STL (Standard Triangle Language) data of upper and lower jaw models acquired with an intraoral scanner. From the STL data of 20 patients, 120 cross-sectional images were generated by three practitioners and compared with the cross-sectional images of 20 patients generated later, and the degree of agreement calculated by AKAZE was analyzed. Statistically significant differences were found between images of the same and different models, and statistically significant differences were obtained when comparing one-sided images with limited information, suggesting that partial dentition information can be used to identify the same dentition.

The role of 3-dimensional printed models in the management of the distal radius fractures.

This study aimed to compare inter- and intra-observer agreement between radiographs with 2-dimensional and 3-dimensional computed tomography scans with and without 3-dimensional printed models in the evaluation of the distal radius fracture of Association for Osteo synth esis/ Ortho paedi c Trauma Association type C classification. Fifteen consecutive cases with X-Rays, 2-dimensional and 3-dimensional computed tomography reconstructions views, and 3-dimensional printed models were selected. Three-dimensional printed models of the distal radius fractures were created using 2-dimensional computed tomography scan files in Digital Imaging and Communication in Medicine format, processed with the 3-dimensional Slicer software, and segmented, creating a 3-dimensional printed model in Standard Triangle Language format. Threedimensional models were printed using fused deposition modeling (FDM) type 3D printer Zortrax M200Plus using polylactic acid material on a scale of 1 : 1. Twenty observers were invited into the study. Intra- and inter-observer reliability was analyzed using Fleiss' kappa statistics. Overall kappa values for both groups in interobserver agreement range from 0.113 to 0.283 and in intra-observer agreement from 0.25 to 0.545. Generally, inter-observer agreement increased with additional 3-dimensional printed models from slight to fair, and intra-observer agreement increased from fair to moderate. Surgeons' opinions about 3-dimensional printed models with Likert scale-type questions show positive overall results ranging from 8.3± 2.1 to 8.6 ± 1.4. This study has shown that the inter- and intra-observer agreement with the addition of a 3-dimensional printed model for the evaluation of the distal radius fractures of Association For Osteo synth esis/ Ortho pedic Trauma Association C type for classification, fractures morphology, and preoperative planning tends to increase; however, improvements for an inter-observer agreement remain fair. Level III Diagnostic Study.

3D FEM Simulation of Titanium Alloy (Ti6Al4V) Machining with Harmonic Endmill Tools

AbstractUsually, end milling operations have been carried out using conventional uniform helix tools with fixed helix angles. Thus, many studies have been conducted to study the effects of these tools on the thermomechanical properties of a milling process. Recently, there have been works that point to the benefits of using harmonic endmills. Harmonic endmills consist of cutting edge profiles that have continuously harmonically varying helix angles. The variation is described using a harmonic function of axial position (elevation) of points on the cutting edge. In this work, a 3D finite element simulation using ABAQUS, is carried out for the complex milling process of Titanium alloy Ti6Al4V. The envelope of the harmonic tool is first generated using a set of MATLAB codes and stored in a Standard Triangle Language (.stl) format. The machine tool is introduced into an FEM program which has been designed to provide for dynamic effects, thermo‐mechanical coupling, material damage law and the criterion for contact associated with the milling process. A Johnson‐Cook material constitutive equation which combines the effects of strain hardening, strain softening, and temperature softening is used. To account for the chip separation criterion, the Johnson Cook damage evolution equation is used. The milling process simulation for Ti6Al4V is then carried out. In the end, the stress distribution and the cutting forces are obtained.

Prototyping and 3D Printing of Computed Tomography Images with an Emphasis on Soft Tissues, Especially Muscles, for Teaching Human Anatomy

The study on cadavers, although considered fundamental in the teaching of human anatomy, is limited in several universities, mainly due to the acquisition and manipulation of cadaveric material. Throughout history, several artificial anatomical models have been used to complement the real anatomical pieces. The present study offers a new alternative: the making of three-dimensional models from Computed Tomography (3D-CT) patient image acquisition. CT images from the USP University Hospital database were used. Patients underwent examinations for reasons other than the present study and were anonymized to maintain confidentiality. The CT slices obtained in thin cross-sections (approximately 1.0 mm thick) were converted into three-dimensional images by a technique named Volume Rendering for visualization of soft tissue and bone. The reconstructions were then converted to an STL (Standard Triangle Language) model and printed through two printers (LONGER LK4 Pro® and Sethi S3®), using PLA and ABS filaments. The 3D impressions of the thigh and leg muscles obtained better visual quality, being able to readily identify the local musculature. The images of the face, heart, and head bones, although easily identifiable, although seemed to present lower quality aesthetic results. This pilot study may be one of the first to perform 3D impressions of images from CT to visualize the musculature in Brazil and may become an additional tool for teaching.

Comparison of Dental Surgical Guides Created by Additive Manufacturing

The presented work deals with the analysis and testing of surgical guidance systems in the dental field, which were created based on available software. When manufacturing dental guidance systems, it is important to consider factors such as the digitization process in the production process, design, selection of the most suitable material and method of implantation. Three types of surgical guidance systems were made by three different devices which work on the principle of additive technology and were closely analysed. Subsequently, the created surgical guidance systems were compared with Standard Triangle Language (STL) files in Gom Inspect software, to determine the accuracy of printed objects. In conclusion, it is important to note that the presented work is a pilot study, which is focused on the design of a methodology to produce surgical guides using 3D printing, taking into account shape accuracy.

Performance of high-translucent zirconia CAD/CAM fixed dental prostheses using a digital workflow: A clinical study up to 6 years

Background/purposeZirconia has recently become a popular material for fixed restorations. The purpose of this study was to use a digital workflow to fabricate monolithic zirconia fixed dental prostheses (FDPs) and assess the connection between variable connector sizes compared to their clinical performance. Materials and methodsClinicians evaluated monolithic zirconia FDPs in 58 patients. After definitive impressions were made, stone casts were obtained. The stone casts were scanned to a standard triangle language (STL) file. A digital wax up was fabricated, and corresponding provisional restorations were milled. Final FDPs were fabricated from a high-translucent zirconia material. During digital fabrication, the connector area of each FDP was recorded while meticulous attention was paid to ensure that the connector cross-sectional area was ≥9 mm2 for the 3-unit restorations (pontic to retainer) and ≥12 mm2 for the 4-unit restorations (pontic to pontic). Biological an technical outcomes of the FDPs were performed at 1 week, 6 months and then annually for 6 consecutive years. ResultsA total of 23 men and 35 women received a total of 63 full-contour zirconia FDPs in the posterior regions and were observed for a time period ranging between 50 and 70 months. No decementation occurred and no caries were detected during the observation period, however signs of gingivitis were detected in 4 patients. The dimension of the connector areas was 12 mm2 in the two broken 4-unit FDPs. ConclusionThe results of this study suggest that the use of digital scanning and milling to fabricate monolithic zirconia FDPs of posterior regions may be an acceptable alternative restorative approach to traditional metal-ceramic restorations.

An Algorithm for Painting Large Objects Based on a Nine-Axis UR5 Robotic Manipulator

An algorithm for automatically planning trajectories designed for painting large objects is proposed in this paper to eliminate the difficulty of painting large objects and ensure their surface quality. The algorithm was divided into three phases, comprising the target point acquisition phase, the trajectory planning phase, and the UR5 robot inverse solution acquisition phase. In the target point acquisition phase, the standard triangle language (STL) file, algorithm of principal component analyses (PCA), and k-dimensional tree (k-d tree) were employed to obtain the point cloud model of the car roof to be painted. Simultaneously, the point cloud data were compressed as per the requirements of the painting process. In the trajectory planning phase, combined with the maximum operating space of the UR5 robot, the painting trajectory of the target points was converted into multiple traveling salesman problem (TSP) models, and each TSP model was created with a genetic algorithm (GA). In the last phase, in conformity with the singularities of the UR5 robot’s motion space, the painting trajectory was divided into a recommended area trajectory and a non-recommended area trajectory and created by the analytical method and sequential quadratic programming (SQP). Finally, the proposed algorithm for painting large objects was deployed in a simulation experiment. Simulation results showed that the accuracy of the algorithm could meet the requirements of painting technology, and it has promising engineering practicability.

Guided and definitive full arch with conometric prosthesis

To test a new 3D-printing technology (Hi-Fiber), associated with cono-morse connection implants and conometric caps for retention, to build a final prosthesis to deliver the same day of the computer-guided and immediate loading implant surgery. Male patient (57 years) needed to rehabilitate his masticatory function due to terminal dentition in the lower jaw. We used implants with cono-morse internal connection and the final prosthesis was delivered the same day of the surgery, connected to the immediate implants through conical caps with conical connection, without any screw or cement. The surgery was computer-guided until the implant insertion, then the conical abutments were inserted manually using special instruments to make them parallel for the conical caps. The final prosthesis was built from the initial data (CBCT and 3D printed models) using a new 3D printed fiber glass fiber as a structure for the full arch, that was delivered the same day. Currently, surgical planning software gives the opportunity to export a Standard Triangle Language (STL) format file that contains the information of the location of the implant in a virtual master model. This is possible through an advanced virtual subtraction of implant bodies from digital oral reconstruction. Utilizing a 3D printing process, it is possible to obtain a physical master model with the spaces for the implants or abutments replicas, avoiding the conventional pour in cast process. Once printed, analogs can be positioned easily and accurately into the prototype, and this model can be used to fabricate the immediate prosthesis to utilize after the surgery, a very useful tool, especially if we want to deliver a final one in the same day, reaching a definitive full arch, as in this particular case report we used implants with cono-morse connection (1.5° each side), conometric abutments and conometric caps to fix the full-arch prosthesis (built with a new 3D printed glass-fiber technology and composite). This concept allows us to minimize micro gaps between implants and abutments, and micro-movements of the prosthesis, stabilizing the peri implants environments. The use of a prefabricated - 3D printed glass fiber framework - provisional prosthesis for full-arch immediate loading created from a new printing technology using a patented software and a 3D printed master model seems to be a predictable treatment option when computer-guided implant surgery is performed. This new material, with the possibility to cement the conical caps (as far as the cylinders for the screw-retained prosthesis), allows the clinicians to deliver the same day final prosthesis with optimal mechanical properties (low weight and strength) to ensure comfort and durability to the patients, maintaining aesthetic due to the natural color of the fibers under the composite resins. Cono-morse conometry at the implant/abutment connection ensures a stable interface between the components and conometry at the prosthetic interface ensures a stable environment against the occlusal forces and the micro-movements, allowing us to detach the prosthesis in a few seconds if we want to evaluate (or rebase and fix) the situation of the soft tissues underneath.

A 3-dimensional airway model for tracheobronchial surgery.

A 3-dimensional airway model for tracheobronchial surgery.

Patient-specific simulation for tracheobronchial reconstruction procedures using 3-dimensional operable models: A proof-of-concept study.

Patient-specific simulation for tracheobronchial reconstruction procedures using 3-dimensional operable models: A proof-of-concept study.

3D printing of individual skin brachytherapy applicator: design, manufacturing, and early clinical results.

PurposeOne of the main challenges in facial region brachytherapy is fixation of vendor-delivered standard applicators. Reproducibility can be maintained; however, there are frequent problems with applicator fitting to the skin surface in pleated regions. Manually prepared individual moulds require technological facilities and highly-trained staff. This article presents 3D-printed applicator preparation for a particular patient skin brachytherapy, using low-cost equipment and free software. We described applicator preparation in a step-by-step workflow.Material and methodsThis study demonstrated preparation of a skin brachytherapy applicator for a challenging recurrent tumor located in the nose bridge. During first visit of patient, fiducial markers were placed to enclose treated region. Patient was computed tomography (CT)-scanned, and reconstruction of target volume and surrounding organs at risk (OARs) were performed using treatment planning system (TPS). In TPS on patient’s surface, a 1-cm thick bolus was added as a body of applicator. Inside the bolus, source paths were designed, and pre-plan was prepared. Using Beben – DICOM to standard triangle language (STL) software, the body of applicator and source-paths from pre-planning was transformed into an STL file, which was used as a solid definition in 3D printing.ResultsThe printed applicator fitted very well, and its’ placement was quickly consistent regarding placing and securing. CTV was slightly broader in treatment plan (0.34 cm3 vs. 0.31 cm3), and doses given to CTV were lower, except for V150, which was higher for the realized plan (1.15% vs. 1.83%). All reported doses to OARs were lower in the realized plan.ConclusionsA low-cost 3D printer and widely available PLA filaments seem feasible to produce individual contact applicators for skin brachytherapy. Beben – DICOM to STL software and presented workflow appear to be convenient and simple tool.

Pyg4ometry: A Python library for the creation of Monte Carlo radiation transport physical geometries

Creating and maintaining computer-readable geometries for use in Monte Carlo Radiation Transport (MCRT) simulations is an error-prone and time-consuming task. Simulating a system often requires geometry from different sources and modelling environments, including a range of MCRT codes and computer-aided design (CAD) tools. Pyg4ometry is a Python library that enables users to rapidly create, manipulate, display, debug, read, and write Geometry Description Markup Language (GDML)-based geometry used in MCRT simulations. Pyg4ometry provides importation of CAD files to GDML tessellated solids, conversion of GDML geometry to FLUKA and conversely from FLUKA to GDML. The implementation of Pyg4ometry is explained in detail in this paper and includes a number of small examples to demonstrate some of its capabilities. The paper concludes with a complete example using most of Pyg4ometry's features and a discussion of possible extensions and future work. Program summaryProgram Title:Pyg4ometryCPC Library link to program files:https://doi.org/10.17632/hngmhmh8cx.1Licensing provisions: GPLv3Programming language: Python, C++External routines/libraries: ANTLR, CGAL, FreeCAD, NumPy, OpenCascade, SymPy, VTKNature of problem: Creating computer-readable geometry descriptions for Monte Carlo radiation transport (MCRT) codes is a time-consuming and error-prone task. Typically these geometries are written by the user directly in the file format used by the MCRT code. There are also multiple MCRT codes available and geometry conversion is difficult or impossible between these simulation tools.Solution method: Create a Python application programming interface for the description and manipulation of Geant4 and FLUKA geometries, with full support for the direct reading and writing of their respective geometry description file formats. Form triangular meshes to represent geometric objects for both visualisation of the geometry and to enable the use of advanced mesh-based geometric algorithms. Triangular mesh processing algorithms allow the loading and use of Standard Triangle Language (STL) and CAD/CAM files. Converting from FLUKA to Geant4 requires algorithms to decompose solids to a set of unions of convex solids. Converting from FLUKA to Geant4 requires a number of steps including the replacement of infinite surfaces with finite solids and the automatic elimination of overlaps.

A Mandible with the Temporomandibular Joint-A New FEM Model Dedicated to Strength and Fatigue Calculations of Bonding Elements Used in Fracture and Defect Surgery.

The aim of the study was to develop a new FEM (finite element method) model of a mandible with the temporal joint, which can be used in the numerical verification of the work of bonding elements used in surgical operations of patients with mandibular fractures or defects. Most of such types of numerical models are dedicated to a specific case. The authors engaged themselves in building a model that can be relatively easily adapted to various types of tasks, allowing to assess stiffness, strength and durability of the bonded fragments, taking into account operational loads and fatigue limit that vary in time. The source of data constituting the basis for the construction of the model were DICOM (digital imaging and communications in medicine) files from medical imaging using computed tomography. On their basis, using the 3D Slicer program and algorithms based on the Hounsfield scale, a 3D model was created in the STL (standard triangle language) format. A CAD (computer-aided design) model was created using VRMesh and SolidWorks. An FEM model was built using HyperWorks and Abaqus/CAE. Abaqus solver was used for FEM analyses. A model meeting the adopted assumptions was built. The verification was conducted by analyzing the influence of the simplifications of the temporomandibular joint in the assessment of mandibular strain. The work of an undamaged mandible and the work of the bonded fracture of the mandible were simulated.

Prediction of endotracheal tube size using a printed three-dimensional airway model in pediatric patients with congenital heart disease: a prospective, single-center, single-group study.

BackgroundTo determine the correct size of endotracheal tubes (ETTs) for endotracheal intubation of pediatric patients, new methods have been investigated. Although the three-dimensional (3D) printing technology has been successful in the field of surgery, there are not many studies in the field of anesthesia. The purpose of this study was to evaluate the accuracy of a 3D airway model for prediction of the correct ETT size, and compare the results with a conventional age-based formula in pediatric patients.MethodsThirty-five pediatric patients under six years of age who were scheduled for congenital heart surgery were enrolled. In the pre-anesthetic period, the patient’s computed tomography (CT) images were converted to Standard Triangle Language (STL) files using the 3D conversion program. A Fused Deposition Modelling (FDM) type 3D printer was used to print 3D airway models from the sub-glottis to the upper carina. ETT size was selected by inserting various sized cuffed-ETTs to a printed 3D airway model.ResultsThe 3D method selected the correct ETT size in 21 out of 35 pediatric patients (60%), whereas the age-based formula selected the correct ETT size in 9 patients (26%).ConclusionsPrediction of the correct size of ETTs using a printed 3D airway model demonstrated better results than the age-based formula. This suggests that the selection of ETT size using a printed 3D airway model may be feasible for helping minimize re-intubation attempts and complications in patients with congenital heart disease and/or those with an abnormal range of growth and development.

A Novel Digital Implant Planning Workflow in Patients with Preexisting Metal Restorations: A Technical Report.

A prosthetically-driven virtual implant plan is considered a challenging procedure depending on accurate registration of the three-dimensional optical surface scan and 3D volumetric rendering reconstructed from cone-beam computed tomography (CBCT) images. However, the presence of preexisting metal restorations may significantly negatively influence the registration process. This technical report describes a novel digital workflow to optimize the implant planning outcome for the partially edentulous patient with preexisting metal restorations by accurately aligning the standard triangle language data of the intraoral scanner with the CBCT rendering using a dual-scan technique and an appliance with radiographic markers.

Optimization of semisolid extrusion (pressure-assisted microsyringe)-based 3D printing process for advanced drug delivery application

3D printing of pharmaceutical formulations requires juggling between the material properties and the printing process to achieve the geometry of the 3D printed products with the desired dose and release. The purpose of the current investigation is to identify the material suitability for semisolid extrusion-based 3D printing of advanced drug delivery system. In this study, the semisolid extrusion-based 3D printing technique was optimized to print a controlled release shell as a vehicle/carrier for oral drug delivery system. The consistency of the printable paste was optimized by screening different solvents for the polymer of interest (cellulose acetate as optimum) to achieve the desired continuous and uniform extrudability behavior. The polarity of the solvent played important role in the selection of the suitable solvent for the optimization process. The nozzle shape (tapered tip as optimum) and the nozzle diameter (630 µm as optimum) were found to be also significantly influenced by extrusion behavior. The printing pressure (60 psi) and speed (4 mm/s) were optimized to reach the required rate of extrusion during the 3D printing process. The thickness and the width of the printed layers have contributed to the creation of the standard triangle language (STL) G-code for the printing of the 3D drug delivery system. It was found that the first printed layer deposited on a particular type of substrate plays a significant role to influence the spreadable behavior of extruded materials. Finally, the present study design proposes a rational guideline for the semisolid extrusion-based 3D printing of pharmaceutical products of specific interest for personalized medicine.

Matching Point Clouds with STL Models by Using the Principle Component Analysis and a Decomposition into Geometric Primitives

While repairing industrial machines or vehicles, recognition of components is a critical and time-consuming task for a human. In this paper, we propose to automatize this task. We start with a Principal Component Analysis (PCA), which fits the scanned point cloud with an ellipsoid by computing the eigenvalues and eigenvectors of a 3-by-3 covariant matrix. In case there is a dominant eigenvalue, the point cloud is decomposed into two clusters to which the PCA is applied recursively. In case the matching is not unique, we continue to distinguish among several candidates. We decompose the point cloud into planar and cylindrical primitives and assign mutual features such as distance or angle to them. Finally, we refine the matching by comparing the matrices of mutual features of the primitives. This is a more computationally demanding but very robust method. We demonstrate the efficiency and robustness of the proposed methodology on a collection of 29 real scans and a database of 389 STL (Standard Triangle Language) models. As many as 27 scans are uniquely matched to their counterparts from the database, while in the remaining two cases, there is only one additional candidate besides the correct model. The overall computational time is about 10 min in MATLAB.