Influence of Framework Material and Posterior Implant Angulation in Full-Arch All-on-4 Implant-Supported Prosthesis Stress Concentration

This study evaluated the influence of distal implants angulation and framework material in the stress concentration of an All-on-4 full-arch prosthesis. A full-arch implant-supported prosthesis 3D model was created with different distal implant angulations and cantilever arms (30° with 10-millimeter cantilever; 45° with 10-millimeter cantilever and 45° with 6-millimeter cantilever) and framework materials (Cobalt–chrome [CoCr alloy], Yttria-stabilized tetragonal zirconia polycrystal [Y-TZP] and polyetheretherketone [PEEK]). Each solid was imported to computer-aided engineering software, and tetrahedral elements formed the mesh. Material properties were assigned to each solid with isotropic and homogeneous behavior. The contacts were considered bonded. A vertical load of 200 N was applied in the distal region of the cantilever arm, and stress was evaluated in Von Misses (σVM) for prosthesis components and the Maximum (σMAX) and Minimum (σMIN) Principal Stresses for the bone. Distal implants angled in 45° with a 10-millimeter cantilever arm showed the highest stress concentration for all structures with higher stress magnitudes when the PEEK framework was considered. However, distal implants angled in 45° with a 6-millimeter cantilever arm showed promising mechanical responses with the lowest stress peaks. For the All-on-4 concept, a 45° distal implants angulation is only beneficial if it is possible to reduce the cantilever’s length; otherwise, the use of 30° should be considered. Comparing with PEEK, the YTZP and CoCr concentrated stress in the framework structure, reducing the stress in the prosthetic screw.

DIFFUSION-VACUUM TECHNOLOGY OF MANUFACTURING LARGE AXISYMMETRIC ASSEMBLIES OF METAL MESH MATERIALS FOR HEAT EXCHANGE PATHS

Requirements for improving the reliability, service life, and increasing a specific pulse of liquid-propellant rocket engines justify a need for transfer to new designs and manufacturing technologies of regenerative engine cooling system. The paper describes a advanced diffusion-vacuum technology of manufacturing a regenerative cooling circuit for liquid-propellant rocket engine based on the concept of inter-channel coolant transpiration through a porous metal mesh material. The method of diffusion welding of metal wire mesh in vacuum makes it possible to obtain large axisymmetric blanks of metal mesh materials necessary to manufacture the regenerative cooling path of the liquid-propellant rocket engine and recuperative heat exchanger (RHE). The possibility of developing a high-efficient low-gradient porous heat exchange path obtained using a metal mesh material (MMM) has been experimentally confirmed. It is recommended to use metal woven cloth and twill filter screens of standard size П24–П60, С120 as a basic material for manufacturing MMM. Key words: diffusion-vacuum technology, porous mesh material, regenerative cooling system, inter-channel coolant transpiration.

Justification of the geometric dimensions of drum sorting machine

This article presents the results of research to determine the basic geometric dimensions of a drum sorting machine designed for potato sorting. A critical analysis of the current situation in this area has been carried out. A number of research works have been studied aimed at developing special methods to reduce manual labour and improve the quality of sizing and sorting potatoes. At the same time, it is important to sort by size with a low level of product damage, with high productivity. Known mechanical and robotic machines used for sorting potatoes: roller, drum, conveyor (belt) and combined. And also, with the help of machine and computer vision, laser backscattering of light, ultrasonic, visual and spectral analysis systems, optical, acoustic intelligent sorting systems. Among the mechanical ones, the drum sorting machine is the simplest in design. The disadvantage of this machine is that during operation the product to be sorted is only in the lower part of the drum, i.e. only part of the work surface is used. To eliminate the abovementioned disadvantage, a new design of the machine is recommended. Where the sorting surface is made of elastic mesh, the size of the holes increased in the direction of movement of the ends along the sorting surface. The ends are connected and pulled together on two drums. The holes of the elastic mesh material vary in size, the size of the holes increases from the beginning to the end of the sorting surface. The drum can be in a truncated cone or a cylinder shape. To ensure the efficient operation of the proposed machine, mathematical calculations are derived, including geometric and kinematic parameters.

Transcatheter Closure of Atrial Septal Defect

Background: Over the past decade, percutaneous atrial septal defect (ASD) closure has been the preferred treatment option in many clinical programs for ASD. Percutaneous ASD closures with advanced device architecture and distribution have established user experience and process security. The ability to diagnose has also improved. The devices have evolved from the larger fixtures to the reset zone, being easily eliminated with little residual mesh material and comfortable fitting with the surrounding structures. Biodegradable technology has been introduced and will be considered as a future option. The emergence of the use of the ASD closure device over the last forty years includes improvements that reduce the incidence of adverse effects reported over the years. Issues reported in the literature include thrombus formation, air tightness, device insertion, abrasion, residual shunts and nickel hypersensitivity. Modern tools hold medium and long-term data with excellent results. Multi-sized devices securely close simple and complex ASDs that can re-scan, reset, and detect percutaneous advanced delivery procedures. In this review, the most widely used tools and distribution processes are discussed and the tools that show promise for the future. Conclusion: As the field of transcatheter treatment of atrial septal defects (TC-ASD) and congenital interventional cardiology develops, real-world design studies provide valuable developmental information on aspects of care where there is disagreement about best practices and more research is needed.

Mesh-related complications and recurrence after ventral mesh rectopexy with synthetic versus biologic mesh: a systematic review and meta-analysis

Background Ventral mesh rectopexy (VMR) is a widely accepted surgical treatment for rectal prolapse. Both synthetic and biologic mesh are used. No consensus exists on the preferred type of mesh material. The aim of this systematic review and meta-analysis was to establish an overview of the current literature on mesh-related complications and recurrence after VMR with synthetic or biologic mesh to aid evidence-based decision making in preferred mesh material. Methods A systematic search of the electronic databases of PubMed, Embase and Cochrane was performed (from inception until September 2020). Studies evaluating patients who underwent VMR with synthetic or biologic mesh were eligible. The MINORS score was used for quality assessment. Results Thirty-two studies were eligible after qualitative assessment. Eleven studies reported on mesh-related complications including 4001 patients treated with synthetic mesh and 762 treated with biologic mesh. The incidence of mesh-related complications ranged between 0 and 2.4% after synthetic versus 0–0.7% after biologic VMR. Synthetic mesh studies showed a pooled incidence of mesh-related complications of 1.0% (95% CI 0.5–1.7). Data of biologic mesh studies could not be pooled. Twenty-nine studies reported on the risk of recurrence in 2371 synthetic mesh patients and 602 biologic mesh patients. The risk of recurrence varied between 1.1 and 18.8% for synthetic VMR versus 0–15.4% for biologic VMR. Cumulative incidence of recurrence was found to be 6.1% (95% CI 4.3–8.1) and 5.8% (95% CI 2.9–9.6), respectively. The clinical and statistical heterogeneity was high. Conclusions No definitive conclusions on preferred mesh type can be made due to the quality of the included studies with high heterogeneity amongst them.

O07 SHORT-TERM OUTCOMES OF A MULTICENTRE PROSPECTIVE STUDY USING A “VISIBLE” PVDF ONLAY MESH FOR THE PREVENTION OF MIDLINE INCISIONAL HERNIA

Aim Prophylactic meshes in high-risk patients prevent incisional hernias, although there are still some concerns about the best layer to place them in, the type of fixation, the mesh material, the significance of the level of contamination, and surgical complications. We aimed to provide answers to these questions and information about how the implanted material behaves based on its visibility under MRI. Material and Methods This is a prospective multicentre observational cohort study. Preliminary results from the first three months are presented. We included general surgical patients who had at least two risk factors for developing an incisional hernia. MRIs were performed six weeks after treatment. A polyvinylidene fluoride (PVDF) mesh loaded with iron particles was used in an onlay position. Results Between July 2016 and December 2020, 178 patients were enrolled in the study. Surgery was emergent in 30.3% of cases, contaminated in 10.7% and dirty in 11.8%. A total of 5.6% of cases had postoperative wound infections, with BMI being the only significant risk factor (OR = 1.14, 95% CI = 1.00-1.31, p = 0.048). The formation of a seroma was also associated with BMI (OR = 1.11, 95% CI = 1.02-1.21, p = 0.02). Conclusions The prophylactic use of onlay PVDF mesh in midline laparotomies in high-risk patients was safe and effective in the short term, regardless of the type of surgery or the level of contamination. MRI allowed us to understand how the mesh behaves during the early process of integration.

Cellulose acetate obtained from Schizolobium parahyba (vell.) blake wood

Currently, non-biodegradable polymers are produced on a large scale and cause several environmental problems, especially due to their low degradation. Cellulose acetate is a non-toxic, low-flammable and low-cost polymer, playing an important environmental role. The objective of this study was to synthesize cellulose acetate membranes from Schizolobium parahyba wood (“guapuruvu”) with particles sizes of 20 and 60 mesh. The materials were submitted to acetosolv pulping, bleaching and acetylation to produce the acetates. The yields and the degree of substitution were found. The fibers were chemically characterized and the samples obtained at each processing step were analyzed by FTIR. It was possible to prepare acetates from both granulometries wood. The FTIR analysis showed changes on the samples’ bands, indicating that the chemical processes were efficient. Cellulose acetate obtained from the 60 mesh material presented a higher degree of substitution (2.74 ± 0.12) when compared to the 20 mesh acetate (2.59 ± 0.13), showing that the particle size of the material influenced on the efficiency of the acetylation reaction. DMA tests have demonstrated that the 60 mesh membrane has higher flexibility and transparency when compared to the 20 mesh membrane.

Treatment of Well Water Using Biosorbent Derived From Areca Fiber Waste

The biosorption of well water using biosorbent from areca fiber waste of Jambi province has been performed to elevate well water quality. In environmental preservation, this research aimed to reduce a solid waste of areca fiber waste, which has only been burned so far. This activity would increase carbon emissions in the atmosphere. These materials were obtained using carbonizations (300 and 400 oC) and without carbonization. The proper material is used as a biosorbent was 400 oC sized 200 mesh. The material showed several functional groups on the biosorbent surface, such as hydroxyl, amide, amine, and carbonyl. Interestingly, using this material, the water quality can be increased by treatments of odor, color, pH, TDS, TSS, and E. coli under conditions 1.25 g biosorbent, 50 oC, and 150 rpm for 30 minutes. The adsorption results were compared with the value from the standard of Permenkes No.146/Menkes/Per/IX/1990. Based on the explanation, it is resumed that biosorbent derived from areca fiber waste is effective, inexpensive, and easy to operate for increasing well water quality.Abstrak: Adsorpsi air sumur menggunakan biosorbent dari limbah sabut pinang Provinsi Jambi telah dilakukan untuk meningkatkan kualitas air sumur. Pada pelestarian lingkungan, penelitian ini bertujuan untuk mengurangi limbah padat sabut pinang, yang selama ini hanya dibakar. Kegiatan ini akan meningkatkan emisi karbo ke atmosfir. Material-material ini diperoleh menggunakan karbonisasi (300 dan 400 oC) dan tanpa karbonisasi. Material yang tepat digunakan sebagai biosorben adalah 400 oC berukuran 200 mesh. Material ini memperlihatkan beberapa gugus fungsi pada permukaan biosorben, seperti hidroksil, amida, amina, dan karbonil. Menariknya, penggunaan material ini, kualitas air dapat ditingkatkan menggunakan treament aroma, warna, pH, TDS, TSS, dan E.Coli pada kondisi 1,25 gram biosorben, 50 oC, 150 rpm, dan selama 30 menit. Hasil adsorpsi dibandingkan dengan nilai standar Permenkes No.146/Menkes/Per/IX/1996. Berdasarkan penjelasan, hal ini disimpulkan bahwa biosorben dari limbah sabut pinang efektif, dan mudah untuk menggunakan untuk meningkatkan kualitas air sumur.