Laser Sintering Research Articles

Effect of different 3D-printing systems on the flexural strength of provisional fixed dental prostheses: a systematic review and network meta-analysis of in vitro studies

ObjectivesThe aim of this systematic review and network meta-analysis was to compare the flexural strength of provisional fixed dental prostheses (PFDPs) fabricated using different 3D printing technologies, including digital light processing (DLP), stereolithography (SLA), liquid crystal display (LCD), selective laser sintering (SLS), Digital Light Synthesis (DLS), and fused deposition modeling (FDM).Materials and methodsA comprehensive literature search was conducted in databases including PubMed, Web of Science, Scopus, and Open Grey up to September 2024. Studies evaluating the flexural strength of PFDPs fabricated by 3D printing systems were included. A network meta-analysis was performed, using standardized mean differences (SMDs) and 95% confidence intervals (CIs) to assess the effects of each system on flexural strength.ResultsA total of 11 in vitro studies were included, with 9 studies contributing to the network meta-analysis. SLS (77.70%) and SLA (63.82%) systems ranked the highest in terms of flexural strength, while DLP ranked the lowest (23.40%). Significant differences were observed between SLS and multiple other systems, including DLP (-14.58, CI: -22.67 to -6.48), LCD (-14.65, CI: -25.54 to -3.59), FDM (-12.87, CI: -23.30 to -2.52), SLA (-11.41, CI: -18.74 to -4.01), and DLS (-10.89, CI: -21.23 to -0.67). Direct comparisons were limited, with DLP vs. SLA having the most data. Other comparisons were predominantly indirect.ConclusionsSLS and SLA systems exhibited superior flexural strength compared to other systems. However, the limited number of direct comparisons and reliance on indirect evidence suggest that further research is necessary to confirm these findings.

Mechanical properties and microbial assessment of additively manufactured diamond and gyroid Ti-6Al-4V ELI scaffolds for interbody fusion cages applications

Abstract This study investigates the mechanical behaviour and microbial assessment of additively manufactured porous titanium scaffolds for interbody fusion cages applications. This study is meticulously designed to focus on both the mechanical and microbial assessments. Two types of cubic porous structure scaffolds were manufactured. The type 1 scaffold was designed with a diamond structure, featuring a pore size of 500 microns and 65% porosity. Similarly, the type 2 scaffold was designed with a gyroid structure, having a pore size of 500 microns and 65% porosity. Both the types of scaffolds were manufactured using direct selective laser sintering technique. Both the group of scaffolds tested for quasi static compression testing, fatigue compression testing, compression torsional testing and corrosion testing for mechanical properties evaluation. For microbial evaluation, bio burden tests, total organic carbon and total hydrocarbon tests were conducted on the both type of scaffolds. Static compression testing results reported that there is no significant effect on the compression strength properties. Diamond scaffolds had higher yield force value than gyroid scaffolds. Fatigue compression and compression - torsional results reported the higher endurance strength of diamond scaffolds over the gyroid scaffolds. There was no significant difference reported for corrosion behavior of both scaffolds. In the present study, both types of scaffolds demonstrated an almost negligible biological burden. The total organic carbon and hydrocarbons values reported were also under permissible limit as per ISO 19227.Results demonstrated several advantages such as higher endurance strength of diamond scaffolds over gyroid scaffolds, highly corrosion resistance and negligible bio burden limits.

Benchmarking artifact of selective laser sintering (SLS) components fabricated with flexible and rigid polymers

Abstract This study aims to assess the performance of an Additive Manufacturing (AM) machine, specifically a Selective Laser Sintering (SLS) machine, through the design and evaluation of a benchmarking artifact. Drawing from insights gained in previous research, the artifact is meticulously crafted with two distinct materials to explore potential variations in geometric accuracy. The artifact comprises two types: one featuring straight geometries and another incorporating curved elements. The research methodology involves printing both artifact types at default machine settings, followed by precise measurements using a 3D scanner. The inclusion of straight and curved features facilitates a comprehensive examination of the machine’s ability to reproduce diverse geometries. The amalgamation of these features into a combined artifact provides a holistic assessment of the machine’s overall performance. To validate the benchmarking artifact, the final design is reproduced, and its output is compared not only with the original design but also with real-life parts. The results show that flexible polymers offer higher accuracy but lower resolution, while rigid polymers provide better resolution but with a greater number of defects. This comparative analysis serves to highlight the accuracy and reliability of the benchmarking artifact in reflecting the machine’s performance in practical scenarios. In conclusion, this study endeavours to advance the understanding of an SLS machine’s capabilities by leveraging a carefully designed benchmarking artifact.

Evaluation of osseointegration of plasma treated polyaryletherketone maxillofacial implants

Osseointegration is a crucial property of biomaterials used for bone defect repair. While titanium is the gold standard in craniofacial surgeries, various polymeric biomaterials are being explored as alternatives. However, polymeric materials can be bioinert, hindering integration with surrounding tissues. In this investigation, plasma ion immersion implantation (PIII)-treated polyether ether ketone (PEEK) and polyether ketone (PEK) implants were assessed in a sheep maxilla and mandible model. Defects were filled with PIII-treated PEEK and PEK implants, produced through fused filament fabrication (FFF) and selective laser sintering (SLS), respectively. Positive controls were grade 23 titanium implants via selective laser melting, while untreated PEEK implants served as negative controls. Surface analyses using scanning electron microscopy and atomic force microscopy revealed favorable properties. Osseointegration was qualitatively and quantitatively assessed at 8-, 10-, and 12-weeks post-implantation, showing significantly improved outcomes for both PIII-treated PEEK and PEK implants compared to untreated controls. The study suggests PIII treatment enhances FFF-printed PEEK’s osseointegration, and PIII-treated SLS-printed PEK achieves comparable osseointegration to 3D printed titanium. These findings underscore surface modification strategies’ potential for polymeric biomaterials, offering insights into developing alternative implant materials for craniofacial surgeries, with enhanced biocompatibility and osseointegration capabilities for improved clinical outcomes.

Porous carbons with complex 3D geometries via selective laser sintering of whey powder

In addition to the inherent limitations of carbons to melt or flow, a vast majority of carbon precursors deforms during carbonisation, with stereolithography of thermoset resins being the preferred technology for 3D printing of carbons. An alternative is now presented with the possibility of using a melting-based technology, selective laser sintering (SLS), to fabricate 3D structures that withstand carbonisation. The key factor that makes this happen is whey powder, a natural, abundant and cheap by-product of the dairy industry. When heating the whey powder with a laser at 180–200 ºC for a few seconds, whey particles sinter, and 3D structures are obtained layer-by-layer. Carbonisation of the sintered whey structures brings about 3D porous carbons with excellent mechanical properties that preserve the SLS printed form albeit an isotropic shrinkage (approx. 23%). Melanoidins are identified as responsible for both the sintering and the thermoset behaviour during carbonisation of the whey powder.

Sacrificial Layer for Sintering Enhancements of Ceramic, Semiconductor, and Metal Films: A Universal Strategy.

The manufacturing of thin films through selective laser sintering of micro/nanoparticles is an emerging technology that has been developing rapidly over the last two decades owing to its digitization, efficiency, and good adaptability to various materials. However, high-quality laser sintering of different materials remains a challenge: ceramic particles are difficult to be sintered due to low absorbance; metallic particles are prone to oxidation; semiconductor particles are difficult to process for performance enhancement due to high stress. In this work, a new approach is proposed that employs an additional Indium Tin Oxide (ITO) sacrificial layer to assist laser sintering of different functional materials, which detaches after sintering without contaminating the target material. As a laser absorber, the ITO layer can raise the sintering temperature up to 2950 K, resulting in well coarsening of ceramic grains. As an oxygen barrier, the ITO layer maintains the oxidation level of the metal die below 25%. As a temperature homogenizer, the ITO layer delays the cracking and improves the performance of the semiconductor material, which in turn increases its Seebeck factor to 1.4-fold. Therefore, the ITO sacrificial layer is a material-friendly, purity-neutral laser sintering strategy, which supports laser sintering of multi-materials and high-performance thin-film devices.

Experimental investigations into corrosion behaviour of DMLS manufactured Ti6Al4V alloy in different biofluids for orthopedic implants

Ti6Al4V alloy is widely used in the biomedical implants industry due to the excellent combination of biocompatibility, mechanical strength & corrosion properties. However, long-time use of Ti6Al4V implants may result in degradation at surge due to corrosive conditions of the human body. In this study, a three-electrode electrochemical cell was used to investigate the corrosion behavior of Ti6Al4V alloy parts manufactured using direct metal laser sintering (DMLS) and conventional cast technique. The corrosion behaviour of Ti6Al4V alloy was investigated in three different biofluids (corrosion media) physiological saline solution (PSS), simulated body fluid (SBF), and phosphate-buffered saline (PBS) using the potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) test. The relevant results showed that the DMLS-produced Ti6Al4V alloy has ~22% higher corrosion resistance than the conventionally cast Ti6Al4V alloy in all three biofluids. The microstructural study revealed that it is due to the fine grains and martensitic microstructure of DMLS-produced samples. Additionally, the DMLS-produced Ti6Al4V alloy in SBF has the lowest corrosion rate of 3.44×10−4 mm per year and exhibits the highest polarization resistance of 3364 Ω.cm2 due to the formation of a stable passive film. Apart from corrosion, the surface characteristics of the corroded samples were also studied using hardness and wettability tests. Additionally, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were also performed to understand the reason behind the results obtained. From all these results, it concluded that the corrosion resistance of the cast and DMLS-produced Ti6Al4V alloy in all three biofluids followed the order of PSS <PBS <SBF.

Fabrication of Free-Standing Porous BaTiO Thick Films by Indirect Selective Laser Sintering

The fabrication of free-standing porous thick films of ferroelectric BaTiO3, using a laser-assisted technique, is presented as a novel alternative to conventional methods. This approach adapts Indirect Selective Laser Sintering (ISLS) to create green films in a single laser pass, avoiding the complexities of traditional processes. Using commercial BaTiO3 powder and polyamide 12 as raw materials, laser processing parameters such as scanning laser speed and power were optimized to produce green BaTiO3 thick films with different thicknesses. After laser processing, the films were conventionally sintered and characterized for phase composition, microstructure, porosity, and electrical properties. X-ray diffraction and Raman spectroscopy confirmed the tetragonal BaTiO3 phase, while mercury intrusion porosimetry revealed a bimodal pore distribution. Impedance spectroscopy demonstrated a positive temperature coefficient of resistivity (PTCR) effect, with a peak resistivity near the Curie temperature. The PTCR behavior is hypothesized to arise from better oxygen adsorption due to the porosity and oxygen vacancies generated during sintering by carbon residues from polyamide degradation. The results demonstrate that ISLS is a versatile technique for producing high-quality, free-standing porous ceramic thick films with potential for a wide range of applications.

Investigation of factors affecting the sound absorption behaviour of 3D printed hexagonal prism lattice polyamide structures

The aim of this work is to investigate the sound absorption properties of open-porous polyamide 12 (PA12) structures produced using Selective Laser Sintering (SLS) technology. The examined 3D-printed samples, fabricated with hexagonal prism lattice structures, featured varying thicknesses, cell sizes, and orientations. Additionally, some samples were produced with an outer shell to evaluate its impact on sound absorption. Experiments were conducted using the transfer function method with an acoustic impedance tube in the frequency range of 250 Hz and 6400 Hz. The results showed that the studied geometric factors significantly affected the sound absorption of the PA12 samples. In some cases, the hexagonal prism lattice structures demonstrated relatively high sound absorption properties. Thanks to their properties such as lower weight, recyclability, and resistance to moisture and chemicals, these structures become competitive with commonly used sound-insulating materials, making them promising candidates for sound absorption. Furthermore, numerical simulations using Ansys software confirmed that the sound absorption properties of the open-porous material structures generally increased with higher specific airflow resistance. The findings highlight the advantages of 3D printing technology in producing complex, highly customizable porous structures for noise reduction applications.

Research of the method of selective laser sintering for strengthening soil tillage working organs

One of the technologies for increasing the service life of working bodies is applying a hardening layer with a material that is more resistant to wear. The study was conducted to evaluate the efficiency of the selective laser sintering (SLS) method for hardening soil-cultivating working bodies. The plasma-powder surfacing method was considered as a comparison option. The studies were conducted on a circular soil test bench, which was a rotor with racks rotating in a cylinder filled with an abrasive medium for rapid surface wear, on which samples were attached. Four experimental samples made of 30KhGSA steel were studied. The dimensions of the hardening layer were determined by calculation. After that, it was applied with P6M5 metal powder using the SLS method to 2 samples, one was hardened before heat treatment, the second after. Similarly, but using FBH-6-2 powder, 2 samples were made using plasma-powder surfacing. The bench test duration was 152 h. The linear wear of the samples when hardened by the SLS method before heat treatment was 1.3 mm, after heat treatment – 0.83 mm, by the plasma method – 1.1 mm and 1.2 mm, respectively. The hardness values that stand out from the others, with the SLS method are observed in the hardening layer zone: the sample before heat treatment is 65 HRC, after it – 73 HRC. With the plasma method, the difference in hardness is observed in the zone near the hardening layer: before heat treatment – 45 HRC, after – 35 HRC. The use of the selective laser sintering method for hardening the blade part of the experimental samples ensured a decrease in the consumption of metal powder, in comparison with the plasma method, by 32 %, an increase in wear resistance of the samples according to the calculated data – by 26 %, on the circular soil stand – by 24 %.

Selective Laser Sintering 3D Printing of Carvedilol Tablets: Enhancing Dissolution Through Amorphization

Background/Objectives: Selective laser sintering (SLS) is one of the most promising 3D printing techniques for pharmaceutical applications as it offers numerous advantages, such as suitability to work with already approved pharmaceutical excipients, the elimination of solvents, and the ability to produce fast-dissolving, porous dosage forms with high drug loading. When the powder mixture is exposed to elevated temperatures during SLS printing, the active ingredients can be converted from the crystalline to the amorphous state, which can be used as a strategy to improve the dissolution rate and bioavailability of poorly soluble drugs. This study investigates the potential application of SLS 3D printing for the fabrication of tablets containing the poorly soluble drug carvedilol with the aim of improving the dissolution rate of the drug by forming an amorphous form through the printing process. Methods: Using SLS 3D printing, eight tablet formulations were produced using two different powder mixtures and four combinations of experimental conditions, followed by physicochemical characterization and dissolution testing. Results: Physicochemical characterization revealed that at least partial amorphization of carvedilol occurred during the printing process. Although variations in process parameters were minimal, higher temperatures in combination with lower laser speeds appeared to facilitate a greater degree of amorphization. Ultimately, the partial conversion to the amorphous form significantly improved the dissolution of carvedilol compared to its pure crystalline form. Conclusions: Obtained results suggest that the SLS 3D printing technique can be effectively used to convert poorly water-soluble drugs to their amorphous state, thereby improving solubility and bioavailability.

Parametric Design and Mechanical Characterization of a Selective Laser Sintering Additively Manufactured Biomimetic Ribbed Dome Inspired by the Chorion of Lepidopteran Eggs

The current research aims to analyze the shape and structural features of the eggs of the lepidoptera species Melitaea sp. (Lepidoptera, Nympalidae) and develop design solutions through the implementation of a novel strategy of biomimetic design. Scanning electron microscopy (SEM) analysis of the chorion reveals a medial zone that forms an arachnoid grid resembling a ribbed dome with convex longitudinal ribs and concave transverse ring members. A parametric design algorithm was created with the aid of computer-aided design (CAD) software Rhinoceros 3D and Grasshopper3D in order to abstract and emulate the biological model. A series of physical models were manufactured with variations in geometric parameters like the number of ribs and rings, their thickness, and curvature. Selective laser sintering (SLS) technology and Polyamide12 (nylon) material were utilized for the prototyping process. Quasi-static compression testing was carried out in conjunction with finite element analysis (FEA) to investigate the deformation patterns and stress dispersion of the models. The biomimetic ribbed dome appears to significantly dampen the snap-through behavior that is observed in typical solid and lattice domes, decreasing dynamic stresses developed during the response and preventing catastrophic failure of the structure. Increasing the curvature of the ring segments further reduces the snap-through phenomenon and improves the overall strength. However, excessive curvature has a negative effect on the maximum sustained load. Increasing the number and thickness of the transverse rings and the number of the longitudinal ribs also increases the strength of the dome. However, excessive increase in the rib radius leads to more acute snap-through behavior and an earlier failure. The above results were validated using respective finite element analyses.

Evaluation of the shear bond strength of surface-treated cobalt-chromium metal crowns on Corticobasal® implant abutments cemented using different luting agents.

This in-vitro study aimed to compare the shear bond strength (SBS) of cobalt-chromium (Co-Cr) crowns on Corticobasal® implant abutments, evaluating the effects of two surface treatments and two luting agents. Thirty Co-Cr crowns were fabricated using CAD-CAM technology with a direct metal laser sintering process and divided into three groups based on surface treatment: Group I (untreated), Group II (sandblasted with 50 μm Al₂O₃), and Group III (Er: YAG laser etching). Each group was further subdivided based on luting cement: Sub group A (GC Fuji Plus) and Sub group B (Rely X U200). This resulted in a total of six groups. The implants were stabilized in auto-polymerizing acrylic resin, and cementation followed standardized protocols. Thermocycling with 1000 cycles (5 °C-55 °C) simulated oral conditions. SBS was tested using a universal testing machine at a crosshead speed of 1 mm/min. Failure patterns were analyzed using stereomicroscopy to classify adhesive, cohesive, and mixed failures. Statistical analysis was performed using one-way ANOVA and Bonferroni post-hoc tests (p < 0.05). Group IIIA (laser-treated, GC Fuji Plus) showed the highest SBS (243.15 MPa), followed by Group IIA (sandblasted + GC Fuji Plus), at 231.81 MPa. The lowest SBS was observed in Group IB (untreated, Rely X U200) at 124.24 MPa. Both sandblasting and laser treatment significantly enhanced SBS, with GC Fuji Plus consistently outperforming Rely X U200. A significant difference of 48.17 MPa was observed between laser-treated Groups IIIA and IIIB (p < 0.01). Laser etching and GC Fuji Plus cementation provided the highest SBS for Co-Cr crowns on Corticobasal® implants. Sandblasting was a secondary effective treatment, while untreated crowns exhibited the weakest bond strength.

Computer-Aided High Tibial Osteotomy-A Comparative Study of Commonly Used 3D Printing Technology and Navigation Application.

High tibial osteotomy (HTO) is a surgical procedure for treating certain knee conditions. Proper execution of HTO can preserve joint function and delay or avoid the need for total knee replacement. This study compared different 3D printing techniques (fused deposition modeling, selective laser sintering, and direct metal laser sintering) and a navigation system for their suitability in assisting HTO surgeries. Tibial saw-bones were used as models, and surgical guides and the navigation system were employed during the procedures. Six parameters (planning time, manufacturing time, delivery time, material cost, operation time, and accuracy) were evaluated. One-way analysis of variance (ANOVA) and t-test were used for the analysis. The results showed that the metal surgical guides had the highest accuracy (angle differences mean, 2.4°) and operation time (mean 9.75 min), followed by plastic guides, classic guides, and the navigation system. The differences in accuracy were attributed to factors like rigidity, melting point, and errors during incisions. The study recommended metal surgical guides as the best option for assisting HTO due to their accuracy and operation time. And the results have implications for orthopedic surgeons performing HTO surgeries, as they can use this information to improve postoperative outcomes, such as mechanical axis alignment and quality of life for HTO patients.

Investigating the impact of design parameters on the clearance in non-assembly mechanisms fabricated by selective laser sintering

Investigating the impact of design parameters on the clearance in non-assembly mechanisms fabricated by selective laser sintering

Selective laser sintering for printing bilayer tablets.

In this study Selective Laser Sintering (SLS) was used to produce bilayer tablets containing rosuvastatin and acetylsalicylic acid. Initially, monolithic tablets of each drug were manufactured using different laser intensities in order to identify their impact on the tablet's dissolution, friability and hardness. After the optimization, the final bilayer tablet was fabricated using a new method, that allowed the printing using different powder blends. For that, a 3D-printed casing was employed to maintain the compartments of the tablet in the correct position during the printing process. The results demonstrated that the increased laser intensities led to denser inner cores, enhanced hardness, decreased friability, and slower drug release. Moreover, the new method was able to produce bilayer tablets completely aligned, showing a minor impact on dissolution when the two compartments were printed together in a single tablet. The work demonstrated the feasibility of using SLS in the production of multi-material drug delivery systems.

Chess-like Pieces Realized by Selective Laser Sintering of PA12 Powder: 3D Printing and Micro-Tomographic Assessment.

The paper highlights the realization of 3D-printed parts with complex geometries, such as chess-like pieces, using polyamide 12 (PA12) as polymeric powder via selective laser sintering (SLS). The research activity focuses on the study of the powder printability, the optimization of the printing parameters, and the tomographic evaluation of the printed objects. Morphological analyses were carried out to study the PA12 powder microstructure considering that SLS required specific particle size distribution and shape, able to guarantee a good flowability necessary to take part in a sintering process. DSC and TG analyses were performed to determine the sintering window and the crystallinity degree, and to evaluate the thermal stability of the PA12 powder due to the importance of the powder processability for the SLS process. The novelty lies in the realization of chess-like pieces very challenging to print via SLS due to their different and highly detailed structures, and the in-depth analysis of the dimensional accuracy evaluated by micro-tomography. The 3D-printed samples obtained show high printing quality and dimensional stability. The μ-CT analysis also confirms the key role of the object shape and section changes on the final porosity of the chess-like pieces.

Evaluation of Recycled and Reused Metal Powders for DMLS 3D Printing.

Metal powders for additive manufacturing are expensive, and producing new ones from mined metals has a negative ecological impact. In this work, recycled and reused metal powders from MS1 steel for direct metal laser sintering (DMLS) 3D printing were evaluated in the laboratory. The powders were recycled by melting followed by gas atomizing. Virgin, recycled, and reused metal powders were evaluated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), metallography analysis, microhardness measurements, particle size distribution (PSD), shape factor by digital image processing (DIP), and flowability testing. The results showed that the particle distribution was modified after recycling. Kurtosis analysis revealed a reduction from -0.64 for virgin powders to -1.29 for recycled powders. The results demonstrated a positive skewness, indicating that the recycled powder contained a greater proportion of smaller particles. The shape factor was also modified and changed from 1.57 for virgin powders to 1.28 for recycled powders. The microstructure also changed, and austenite was found in the recycled powders. The microhardness of recycled powder decreased by 39% compared to the virgin powder. Recycled powders did not flow, using two different funnels to evaluate their flowability. The flowability of used powder was reduced from 4.3 s to 2.9 s.

A Review on 3D Printing Technology Used in Pharmaceutical Industry

Three-dimensional printing (3DP) makes it possible to create a variety of geometries using computer-aided design with various materials and procedures for intended uses, such pharmaceutical drug delivery systems. Despite the fact that 3D printing was patented in 1986, 3DP research did not gain traction until the past 10 years. The expectations of regulatory bodies, constraints, challenges in setting up such facilities for the manufacturing of pharmaceutical goods, benefits, drawbacks, uses, techniques, and related manufacturing hazards are all presented here. FDA. When compared to conventional drug preparation methods, 3D printing technology offers substantial benefits for customized drug production, making it simple to create preparations with intricate structures or drug release characteristics and enabling quick production of tiny quantities of medications. It also offers a thorough analysis of the state of this platform's research and development at the moment. The present review aims to provide an overview of the benefits, limitations, and uses of 3D printing in pharmaceutical technology by outlining several techniques (such as thermal ink jet printing, ink jet printing, fused deposition modeling, extrusion 3D printing, zip dose, hot melt extrusion, 3D printer, stereolithography, selective laser sintering, laser-based writing system, continuous layer interface production, and powder-based 3D printing). [15]

Alkylated derivatives of chitosan for stabilization of polylactide microparticles used as building blocks for 3D structures

AbstractModification of the chitosan chemical structure by grafting hydrophobic fragments makes it possible to synthesize derivatives with amphiphilic properties. These derivatives were used as emulsifiers in the aqueous phase during the production of polylactide microparticles via the oil/water solvent evaporation technique. The application of the derivatives allows to achieve a high yield of the microparticles and to provide a hydrophilic coating on the surface of polylactide microparticle. The chitosan‐coated polylactide microparticles were analyzed in terms of mean size, size distribution, surface, and internal morphology. The ability of the obtained microparticles to be used as a starting component for the fabrication of 3D materials through the surface‐selective laser sintering was evaluated, and the optimal parameters for the process have been determined.