Computer-aided Design Procedure Research Articles

Biomechanical Effects of Different Auxiliary–Aligner Designs on the Rotation of an Upper Canine: A Finite Element Analysis of a Specific Patient

Aim: The objective of this research has been to apply a specific simulation to a patient to assess the biomechanical consequences of rotating an upper canine tooth through different attachment–aligner configurations and to predict the most efficient design using a three-dimensional finite element model of a full maxillary arch of a specific patient. Materials and methods: This was obtained by combining Cone-Beam Computed Tomography (CBCT) with the aim of reconstructing tooth roots and bone tissues, and Surface Structured-Light Scanning for creating digital tooth crown models from the patient’s impressions. This model was imported into the finite element solver (Ansys® 17). Three different attachment–aligner combinations were created through the exploitation of computer-aided design (CAD) procedures, i.e., without attachments, with a couple of attachments and with an attachment and a pressure point. For each simulation, the resulting force–moment (MF) system applied by the aligner to the target tooth, as well as the tooth displacement and rotation, was computed using a workstation based on Intel Xeon CPU E3-1245 v3@3.40 GHz and 16 GB RAM. Simulations reported that by adding the pressure point and the attachment to the standard aligner the amount of Moment z (Mz) delivered to the tooth increased almost two times. Results and conclusions: The maximum tooth displacement (0.85 mm) was obtained with the attachment and pressure point aligner, while the lowest (0.058 mm) was obtained with use of a couple of attachments. Both the attachment and the pressure point have the potential to enhance the appliance’s effectiveness. Particularly, the pressure point showed a higher influence on the load absolute value. The method applied in the present study should be used to retrieve the best design configuration for each patient and specific tooth movement.

CAD-CAM fabrication of semiprecision LOCATOR-style abutments to correct severely misaligned implants supporting a 4-implant maxillary overdenture

Implant-supported removable overdentures are a popular treatment option with a favorable impact on a patient’s quality of life. A maxillary removable overdenture without palatal coverage should be supported by at least 4 implants uniformly distributed around the arch and connected by either semiprecision attachments or a bar. Optimally these 4 implants should be parallel or have their long axes nearly aligned to facilitate the prosthodontic phase of treatment by allowing the use of standard components. A computer-aided design and computer-aided manufacturing (CAD-CAM) procedure to produce LOCATOR-style attachments (T-L Custom abutments; TruAbutment Inc) to manage the restoration of 4 misaligned implants is described.

Repurposing FDA-approved drugs as FXR agonists: a structure based in silico pharmacological study.

Farnesoid X receptor (FXR) modulates the expression of genes involved in lipid and carbohydrate homeostasis and inflammatory processes. This nuclear receptor is likely a tumor suppressor in several cancers, but its molecular mechanism of suppression is still under study. Several studies reported that FXR agonism increases the survival of colorectal, biliary tract, and liver cancer patients. In addition, FXR expression was shown to be down-regulated in many diseases such as obesity, irritable bowel syndrome, glomerular inflammation, diabetes, proteinuria, and ulcerative colitis. Therefore, development of novel FXR agonists may have significant potential in the prevention and treatment of these diseases. In this scenario, computer-aided drug design procedures can be resourcefully applied for the rapid identification of promising drug candidates. In the present study, we applied the molecular docking method in conjunction with molecular dynamics (MD) simulations to find out potential agonists for FXR based on structural similarity with the drug that is currently used as FXR agonist, obeticholic acid. Our results showed that alvimopan and montelukast could be used as potent FXR activators and outperform the binding affinity of obeticholic acid by forming stable conformation with the protein in silico. However, further investigational studies and validations of the selected drugs are essential to figure out their suitability for preclinical and clinical trials.

Low-Cost and Highly Accurate Behavioral Modeling of Antenna Structures by Means of Knowledge-Based Domain-Constrained Deep Learning Surrogates

The awareness and practical benefits of behavioral modeling methods have been steadily growing in the antenna engineering community over the last decade or so. Undoubtedly, the most important advantage thereof is a possibility of a dramatic reduction of computational expenses associated with computer-aided design procedures, especially those relying on full-wave electromagnetic (EM) simulations. In particular, the employment of fast replacement models (surrogates) allows for repetitive evaluations of the antenna structure at negligible cost, thereby accelerating processes such as parametric optimization, multi-criterial design, or uncertainty quantification. Notwithstanding, a construction of reliable data-driven surrogates is seriously hindered by the curse of dimensionality and the need for covering broad ranges of geometry/material parameters, which is imperative from the perspective of design utility. A recently proposed constrained modeling approach with knowledge-based stochastic determination of the model domain addresses this issue to a large extent and has been demonstrated to enable quasi-global modeling capability while maintaining a low setup cost. This work introduces a novel technique that capitalizes on the domain confinement paradigm and incorporates deep-learning-based regression modeling to facilitate handling of highly-nonlinear antenna characteristics. The presented framework is demonstrated using three microstrip antennas and favorably compared to several state-of-the-art techniques. The predictive power of our models reaches remarkable 2% of a relative rms error (averaged over the considered antenna structures), which is a significant improvement over all benchmark methods.

Calibrated splinting framework for complete arch intraoral implant digital scans manufactured by combining milled and additively manufacturing technologies: A dental technique

Splinting frameworks are intended to increase the accuracy of complete arch intraoral digital implant scans. This article describes a technique that uses a calibrated splinting framework manufactured by combining milled and additively manufacturing technologies (IOSRing) for assisting with complete arch intraoral digital implant scanning. The splinting framework contains milled truncated cone-shape markers whose position in the metal framework is measured during the manufacturing process with a coordinate measurement machine. This framework splints the modified implant scan bodies and assists in the complete arch intraoral implant digital scanning. Computer-aided design procedures are then used to calculate the implant position on the virtual definitive implant cast by using the position of the calibrated markers as a reference.

Clinical application of automated virtual orbital reconstruction for orbital fracture management with patient-specific implants: A prospective comparative study

The aim of the study was to compare automated and manually conducted (slice-by-slice) virtual orbital wall reconstruction in terms of PSI design, manufacture, and clinical application for orbital fracture management.Patients with orbital wall fractures were evaluated for the potential for treatment with PSI, based on automated virtual wall reconstruction; these formed the main group. The surgical outcomes of these main-group patients' treatments were compared with those of the control group, which comprised patients randomly selected for this study, each of whom had the same orbital trauma patterns and were also managed with PSI. However, the control group patients were treated using ‘slice-by-slice’ virtual orbital reconstruction.Mean volume differences between the intact and reconstructed orbit were 0.65 ± 0.26 cm3 in the main group (n = 23) and 0.57 ± 0.23 cm3 in the control (n = 27; p = 0.837). In both groups, no cases of implant malposition or enophthalmos were detected after surgery. Orbital shape difference was similar for the main group and the control, at −3.3 ± 3.5% and 3.25 ± 2.5%, respectively (p = 0.929). Diplopia was diagnosed at the 3-month follow-up in 13.0% of the main group and in 11.1% of the control (p = 0.651). The average times spent on computer-aided design (CAD) procedures, including segmentation, virtual orbital reconstruction, and PSI design, were 36.7 ± 6.9 min in the main group and 72.9 ± 7.7 min in the control group (p < 0.001).Within the limitations of the study it seems that PSI based on automated virtual reconstruction is a relevant alternative treatment option for orbital fractures because of its clinical efficacy that is similar to PSI based on a ‘slice-by-slice’ CAD protocol.

Workflow for complete dentures fabrication in three appointments: A dental technique

This technical report describes a novel workflow for complete denture fabrication designed to abbreviate the necessary steps for dental prostheses delivery by using a 3-appointment protocol in which preliminary impressions are made in the first session together with the registration of maxillary lip support, occlusal plane, and reference lines for tooth arrangement. A trial denture is fabricated with conventional or computer-aided design and computer-aided manufacturing procedures and is evaluated in the second appointment for esthetics, the definitive impression, and the maxillomandibular relationship record to provide precise references for definitive denture fabrication.

Influence of Infill Patterns Generated by CAD and FDM 3D Printer on Surface Roughness and Tensile Strength Properties

Fused deposition modeling (FDM) is a capable technology based on a wide range of parameters. The goal of this study is to make a comparison between infill pattern and infill density generated by computer-aided design (CAD) and FDM. Grid, triangle, zigzag, and concentric patterns with various densities following the same structure of the FDM machine were designed by CAD software (CATIA V5®). Polylactic acid (PLA) material was assigned for both procedures. Surface roughness (SR) and tensile strength analysis were conducted to examine their effects on dog-bone samples. Also, a finite element analysis (FEA) was done on CAD specimens to find out the differences between printing and simulation processes. Results illustrated that CAD specimens had a better surface texture compared to the FDM machine while tensile tests showed patterns generated by FDM were stronger in terms of strength and stiffness. In this study, samples with concentric patterns had the lowest average SR (Ra) while zigzag was the worst with the value of 6.27 µm. Also, the highest strength was obtained for concentric and grid samples in both CAD and FDM procedures. These techniques can be useful in producing highly complex sandwich structures, bone scaffolds, and various combined patterns to achieve an optimal condition.

In-house tooth-supported guide for the injection of botulinum toxin into the lateral pterygoid muscle using Blue Sky Plan software: A technical note

Hyperactivity of the lateral pterygoid muscle (LPM) is one of the theories postulated to explain anterior disc displacement, which can result in difficulty in jaw opening, jaw protrusion, or jaw-deviation dystonias and interferes with mastication, speech, and swallowing. Injection of botulinum toxin of the LPM is considered a conservative therapeutic modality for this condition.The LPM is a deep facial structure and several techniques have been described that use magnetic resonance imaging, arthroscopic, or electromyographic guidance to perform intramuscular botulinum toxin injection safely this to prevent incorrect injection or complications, such arterial bleeding. This study provided a described step-by-step description of the computer-aided design and manufacturing procedure for the fabrication of an in-house guide to simplify the method of botulinum toxin injection in the LPM and ensure accuracy and safety in medical office.

Design Procedure of A Permanent Magnet D.C. Commutator Motor

Electrical machine with electro magnet as excitation system many problems out of which, less efficiency is a major one. Self excited dc machine has to sacrifice some power for excitation system as a result, power available for useful work become less. This problem can be solved to some extent whatever may be the amount , by using permanent magnet for the excitation system of dc machine and there by contributing towards the conservation of conventional energy sources which are alarmingly decrease day by day . Using of permanent magnet in the electrical machine helps in burning of less conventional fossil fuel and contributes indirectly in conservation of air-pollution free environment. With permanent magnet dc motor, the efficiency of the machine also rise up considerably. This paper is an effort to give a computer aided design procedure of permanent magnet dc motor.

Stress concentration at cruciform welded joints under axial and bending loading modes

The paper is concerned with the problem of stress concentration in cruciform fillet welded joints subjected to axial and bending load. Extended numerical analyses were carried out with the help of the finite element method. It made it possible to estimate stress concentration factors Kt for a variety of geometrical parameters defining the geometry of cruciform welded joints. It has been found that approximate Kt formulas, available in the literature, have two disadvantages, i.e. an unknown accuracy and small range of application with respect to geometrical parameters defining the weld shape. For these reasons, more general and accurate new formulas for stress concentration factors Kt have been derived. Even though the present approach is applicable to all types of welded joints, the analysis presented below has been conducted for a cruciform joint with the weld flank angle of θ = 45°. Final solutions have been given in the form of polynomial expressions, and they can be easily used in computer-aided design procedures.

DIBRAST: A Computer-Aided Seismic Design Procedure for Frame Structures Equipped With Hysteretic Devices

This paper describes a comprehensive computer-aided seismic design approach for both new and existing frame structures equipped with hysteretic dampers. As a matter of fact, despite continuous advancements in the state-of-art demonstrate the effectiveness of these devices in mitigating seismic hazard, nonlinearities involved in the problem and the articulated nature of most of the available design procedures often make them quite difficult to be implemented for real complex structures. To promote widespread use of hysteretic dampers, it is presented a thorough design approach which includes the application of a specific displacement-based design procedure by means of a computer-aided support tool, developed in Visual Basic environment and named DIBRAST. The software is realized to drive the designer through the dissipative system’s design. Required iterations are automated, thus significantly reducing time-processing. As final output, it delivers the damping braces mechanical properties in order to meet a specific performance objective. In order to further support practitioners in geometrical characterization of actual design dampers, authors developed an additional Visual Basic tool, Shear Link Non-Linear Model, able to provide yielding force and elastic stiffness of a specific type of hysteretic device according to its geometry and material. In addition, geometric details of each device can be preliminary determined by means of newly proposed design charts, herein presented, that allow to take into account buckling issue too. Both developed tools are freely available online. A case study is provided to demonstrate the effectiveness of the proposed design approach and tools.

Color dimensions of additive manufactured interim restorative dental material

Statement of problemInterim dental restorations can be fabricated by using additive manufacturing (AM) technologies. Although dental restoration contours can be easily and accurately fabricated by using computer-aided design (CAD) procedures, protocols for creating predictable color dimensions of AM interim restorations are lacking. PurposeThe purpose of this in vitro study was to measure and compare color dimensions of different AM and conventional interim restorative materials. Material and methodsDisks (N=420) were fabricated by using either conventionally (CNV group) or additively manufactured (AM group) materials. The CNV group was further divided into the subgroups CNV-1 (Protemp 4; 3M ESPE) and CNV-2 (Anaxdent new outline dentin; Anaxdent). AM subgroups included AM-1 (FreePrint temp; Detax), AM-2 (E-Dent 400; Envisiontec), AM-3 (NextDent C&B; NextDent), AM-4 (NextDent C&B MFH; NextDent), and AM-5 (Med620 VEROGlaze; Stratasys). Color measurements in the CIELab coordinates were made by using a spectrophotometer (VITA EasyShade Advance 4.0; VITA) with a standardized photography gray card as a background under room light conditions (1003 lux). Color difference (ΔE*) values were calculated by using the CIE76 and CIEDE2000 formulas. The data were analyzed by using the Kruskal-Wallis test with nonparametric pairwise comparisons. ResultsOwing to a software error, the spectrophotometer was unable to measure the color of any specimens in the AM-5 subgroup, which was consequently excluded from further analysis. Significant differences (P=.001) between 2 manufacturing groups were found based on the L* variable. All subgroups were significantly different from each other for all 3 variables (P<.001). Pairwise comparisons revealed that all groups were significantly different from each other, except for the AM-1 and AM-2 subgroups, compared with the CNV-1 subgroup for the L* color dimension. The ΔE* values calculated by using the CIE76 formula varied from 6.63 to 23.1 and by using the CIEDE2000 formula from 3.43 to 10.21, suggesting a perceptible and unacceptable color mismatch between the CNV and AM groups. ConclusionsNone of the additively manufactured interim materials tested matched the conventional interim materials in all 3 CIELab color dimensions.

Biomechanical Effects of Different Auxiliary-Aligner Designs for the Extrusion of an Upper Central Incisor: A Finite Element Analysis.

Aim To evaluate the biomechanical effects of four different auxiliary-aligner combinations for the extrusion of a maxillary central incisor and to define the most effective design through finite element analysis (FEA). Materials and Methods A full maxillary arch (14 teeth) was modelled by combining two different imaging techniques: cone beam computed tomography and surface-structured light scan. The appliance and auxiliary element geometries were created by exploiting computer-aided design (CAD) procedures. The reconstructed digital models were imported within the finite element solver (Ansys® 17). For the extrusion movement, the authors compared the aligner without an attachment with three auxiliary-aligner designs: a rectangular palatal attachment, a rectangular buccal attachment, and an ellipsoid buccal attachment. The resulting force-moment (MF) system delivered by the aligner to the target tooth and the tooth displacement were calculated for each scenario. Results The maximum tooth displacement along the z-axis (0.07 mm) was obtained with the rectangular palatal attachment, while the minimum (0.02 mm) was obtained without any attachments. With the ellipsoid attachment, the highest undesired moments Mx and My were found. The rectangular palatal attachment showed the highest Fz (2.0 N) with the lowest undesired forces (Fx = 0.4 N; Fy = −0.2 N). Conclusions FEA demonstrated that the rectangular palatal attachment can improve the effectiveness of the appliance for the extrusion of an upper central incisor.

Molecular design of solvents for CO2 capture using a group contribution EOS

After a brief revision of the literature, this work develops a computer-aided molecular design procedure (GCMOLD), based on the Group Contribution Equation of State, GC-EOS. The selection of solvents, for CO2 capture in pre-combustion processes by GCMOLD, allows a systematic study of the effect of molecular functionality on solvent properties. For this problem, after the selection of a number of paraffinic and CO2-phylic groups for the synthesis of molecular structures, the GCMOLD program generates a list of solvents ranked by their solvent power. On this basis, the effect of paraffinic and polar structures on solvent power and solvent loss gives a rationale for optimum solvent selection. Finally, an innovative scheme of an absorption cycle with low energy consumption is proposed.

A methodology for the design of dam spillways with wedge shaped blocks based on numerical modeling

Wedge shaped blocks spillways are an innovative solution that allows spilling over the downstream shoulder of earth and rock-fill dams in a safe way. However, they have been barely used as main spillway due to the lack of practical design criteria. An innovative procedure for computer-aided design of wedge shaped blocks spillways is presented in this paper. It includes the design of the drainage and supporting layer considering its seepage capacity and stability. The leakage flow through the joints between blocks is estimated by means of a numerical model calibrated and validated from experimental results. Stability against sliding of the downstream shoulder or the drainage layer is ensured, considering the properties of the granular material selected by the designer and non-linear resistance laws. The procedure will also suggest the shape of a toe protection.

Optimal design and operation of Fischer-Tropsch microchannel reactor for pilot-scale compact Gas-to-Liquid process

Design and operation of pilot-scale (1.0 BDP) compact GTL process comprising of reforming section, CO2 separating section, and Fischer-Tropsch (FT) synthesis section is presented. Detailed systematic computer-aided design procedure adopted to design a modular 0.5 BPD pilot-scale microchannel reactor used in the pilot plant operation is also presented. The modular microchannel FT reactor block design consists of 528 process channels and numerous coolant channels arranged in cross-cocurrent-cross configuration for adequate heat removal. On average 98.27% CH4 conversion to syngas in reforming section comprising of a pre-reformer unit and a tri-reformer unit, and CO2 separation rate of 36.75% along with CO/H2 reduction from 2.67 to 2.08 in CO2 membrane separation section were achieved from the entire pilot plant operation duration of 450 h. Parallel operation of FT microchannel reactor and multitubular fixed-bed type FT reactor for comparison showed that multitubular fixed-bed type reactor undergoes reaction runaway for the applied process conditions, while microchannel reactor showed adequate temperature control. Overall CO conversion of 83% and adequate temperature control at three different applied operating temperatures of 220 °C, 230 °C, and 240 °C subsequently during the 139 h FT reactor operation demonstrated the appreciable performance of the present microchannel FT reactor designed.

Exploring the Tuning Range of Channel Filters for Satellite Applications Using Electromagnetic-Based Computer Aided Design Tools

The objective of this paper is to use electromagnetic-based computer-aided design (CAD) tools to investigate the maximum tuning range of channel filters, typically used in satellite payloads. Both circular and rectangular waveguide technologies are investigated. The results of the investigation show that single-mode rectangular waveguide implementations offer substantially wider tuning range, as opposed to classical dual-mode circular waveguide implementations. In addition to simulations, measurements are also presented indicating very good agreement with theory, thereby fully validating the CAD procedure.

A functional methodology on the manufacturing of customized polymeric cranial prostheses from CAT using SPIF

PurposeThis paper aims to propose a functional methodology to produce cranial prostheses in polymeric sheet. Within the scope of rapid prototyping technologies, the single-point incremental forming (SPIF) process is used to demonstrate its capabilities to perform customized medical parts.Design/methodology/approachThe methodology starts processing a patient’s computerized axial tomography (CAT) and follows with a computer-aided design and manufacture (CAD/CAM) procedure, which finally permits the successful manufacturing of a customized prosthesis for a specific cranial area.FindingsThe formability of a series of polymeric sheets is determined and the most restrictive material among them is selected for the fabrication of a specific partial cranial prosthesis following the required geometry. The final strain state at the outer surface of the prosthesis is analysed, showing the high potential of SPIF in manufacturing individualized cranial prostheses from polymeric sheet.Originality/valueThis paper proposes a complete methodology to design and manufacture polymer customized cranial prostheses from patients’ CATs using the novel SPIF technology. This is an application of a new class of materials to the manufacturing of medical prostheses by SPIF, which to this purpose has been mainly making use of metallic materials so far. Despite the use of polymers to this application is still to be validated from a medical point of view, transparent prostheses can already be of great interest in medical or engineering schools for teaching and research purposes.

Accuracy of impression scanning compared with stone casts of implant impressions

Statement of problemAccurate virtual implant models are a necessity for the fabrication of precisely fitting superstructures. PurposeThe purpose of this in vitro study was to evaluate different methods with which to build an accurate virtual model of a 3-dimensional implant in the oral cavity; this model would then be used for iterative computer-aided design and computer-aided manufacturing (CAD-CAM) procedures. Material and methodsA titanium master model with 3 rigidly connected implants was manufactured and digitized with a noncontact industrial scanner to obtain a virtual master model. Impressions of the master model with the implant position locators (IPL) were made using vinyl siloxanether material. The impressions were scanned (Impression scanning technique group). For the transfer technique and pick-up technique groups (each group n=20), implant analogs were inserted into the impression copings, impressions were made using polyether, and casts were poured in Type 4 gypsum. The IPLs were screwed into the analogs and scanned. To compare the virtual master model with each virtual test model, a CAD interactive software, ATOS professional, was applied. The Kruskal-Wallis test was subsequently used to determine the overall difference between groups, with the Mann-Whitney U test used for pairwise comparisons. Through Bonferroni correction, the α-level was set to .017. ResultsThe outcome revealed a significant difference among the 3 groups (P<.01) in terms of accuracy. With regard to total deviation, for all axes, the transfer technique generated the greatest divergence, 0.078 mm (±0.022), compared with the master model. Deviation with the pick-up technique was 0.041 mm (±0.009), with impression scanning generating the most accurate models with a deviation of 0.022 mm (±0.007). ConclusionsThe impression scanning method improved the precision of CAD-CAM-fabricated superstructures.