The effect of surface treatment and low-temperature degradation on flexural strength of additive manufactured zirconia

This study aimed to assess the effect of low-temperature degradation (LTD) and surface treatment on the flexural strength of additive-manufactured (AM) zirconia by comparison to subtractive-manufactured (SM) zirconia. Disc-shaped zirconia specimens were fabricated using AM and SM technology, and each group was assigned to 3 subgroups according to the type of surface treatment: control, sandblasting (SB), and 9% hydrofluoric acid etching (HF). The groups were then further divided into 2 subgroups: unaged and aged. Biaxial flexural strength, crystal phase, surface topography, and surface roughness were measured to evaluate the mechanical properties. Statistical analyses were performed with 3-way ANOVA, followed by the comparison of means with Bonferroni post hoc analyses. The means and standard deviations of the biaxial flexural strength and Weibull parameters were calculated with descriptive statistics. All SM groups showed significantly greater flexural strength than the AM groups (p < .05), and LTD did not affect flexural strength except for the SMHF group (p < .05). After LTD, monoclinic phases (m-phase) were found in all groups, and SEM images showed grain pullout due to zirconia volume expansion in both control groups. Sandblasting significantly affected flexural strength (p < .05), whereas the HF group did not affect flexural strength except in the SMHF group after LTD (p < .05). No significant difference was observed in the surface roughness of AM compared to SM groups conditioned with the same surface treatment regardless of LTD. AM zirconia has comparable mechanical properties to SM zirconia, regardless of low-temperature degradation and surface treatment, which indicates the potential of the AM technique for clinical applications.

Hypotrochoidal scaffolds for cartilage regeneration

The main function of articular cartilage is to provide a low friction surface and protect the underlying subchondral bone. The extracellular matrix composition of articular cartilage mainly consists of glycosaminoglycans and collagen type II. Specifically, collagen type II fibers have an arch-like organization that can be mimicked with segments of a hypotrochoidal curve. In this study, a script was developed that allowed the fabrication of scaffolds with a hypotrochoidal design. This design was investigated and compared to a regular 0-90 woodpile design. The mechanical analyses revealed that the hypotrochoidal design had a lower component Young's modulus while the toughness and strain at yield were higher compared to the woodpile design. Fatigue tests showed that the hypotrochoidal design lost more energy per cycle due to the damping effect of the unique microarchitecture. In addition, data from cell culture under dynamic stimulation demonstrated that the collagen type II deposition was improved and collagen type X reduced in the hypotrochoidal design. Finally, Alcian blue staining revealed that the areas where the stress was higher during the stimulation produced more glycosaminoglycans. Our results highlight a new and simple scaffold design based on hypotrochoidal curves that could be used for cartilage tissue engineering.

Review on 3D printing techniques for cutting tools with cooling channels

This review paper critically emphasizes the possibilities and recent developments for producing high-performance conventional cutting tools that are in demand in the traditional machining industry. These cutting tools are considered for use in traditional machining of materials that provide a high strength-to-weight ratio for various applications with high precision. This review focuses on the machinability of turning, milling, drilling, and other special tools manufactured using various additive manufacturing methods. The materials and methods used are also studied, enabling us to understand the vast requirements of tool materials and the additive manufacturing methods available for production. The critical suggestions discussed would establish a platform for the selection of printing methods and printing strategies to develop cutting tools with complex internal geometries.

Additive manufacturing and three-dimensional printing in obstetrics and gynecology: a comprehensive review

Three-dimensional (3D) printing, also known as additive manufacturing, is a technology used to create complex 3D structures out of a digital model that can be almost any shape. Additive manufacturing allows the creation of customized, finely detailed constructs. Improvements in 3D printing, increased 3D printer availability, decreasing costs, development of biomaterials, and improved cell culture techniques have enabled complex, novel, and customized medical applications to develop. There have been rapid development and utilization of 3D printing technologies in orthopedics, dentistry, urology, reconstructive surgery, and other health care areas. Obstetrics and Gynecology (OBGYN) is an emerging application field for 3D printing. This technology can be utilized in OBGYN for preventive medicine, early diagnosis, and timely treatment of women-and-fetus-specific health issues. Moreover, 3D printed simulations of surgical procedures enable the training of physicians according to the needs of any given procedure. Herein, we summarize the technology and materials behind additive manufacturing and review the most recent advancements in the application of 3D printing in OBGYN studies, such as diagnosis, surgical planning, training, simulation, and customized prosthesis. Furthermore, we aim to give a future perspective on the integration of 3D printing and OBGYN applications and to provide insight into the potential applications.

Method for predicting the wettability of micro-structured surfaces by continuum phase-field modelling

Numerical prediction of material properties is attracting the attention of the scientific community and industry because of its usefulness in the design process. In the fields of fluid dynamics and microfluidics, several simulation methods have been proposed and adopted to evaluate the properties of surfaces and material interfaces, thanks to the increasing computational power available. However, despite the efforts made, a general and standardized methodology for implementing such methods is still lacking, thus requiring a trial-and-error approach for each new problem, making them difficult to implement and creating a bottleneck at the initial stage of surface design. Here, we report a validated protocol to evaluate the wettability of micro-structured surfaces with a phase-field model. Summarizing:•Simulating physical phenomena with multi-phase flows and moving contact lines can be a challenging task, due to the coupling among disparate length scales.•Using the Cahn-Hilliard diffuse-interface model, moving contact lines can be extensively investigated, although difficulties may arise when implementing numerical simulations, e.g., model parameter calibration, selection of boundary conditions, post-processing of fluid dynamics/equilibrium.•A method for employing this model and evaluating the physical consistency of the results is proposed here, considering the wettability of micro-structured surfaces as a case study.

Introducing microarchitecture into 3D-printed prosthesis socket: Pressure distribution and mechanical performance

This research is aimed at development of 3D-printed sockets for an orthopaedic prosthesis using methods of pressure redistribution on the inner surface of the socket. Topological freedom provided by modern additive manufacturing allows optimization of the parameters of the socket to create an orthopaedic prosthesis with properties adapted to the needs of a particular patient. This paper proposes an approach to redistribute the pressure in the prosthesis by controlled reinforcement with continuous carbon rods to artificially create zones of higher and lower pressure to facilitate prosthetic wear. Numerical modelling is used for the pre-design of a unique internal architecture of the prosthesis, which can redistribute the pressure on the inner surface of the socket, thus relieving excessive pressure from sensitive soft-tissue zones. The influence of socket thickness, inclination angle of the rods and the elastic behaviour of the polymeric materials on the extent of pressure redistribution is investigated.

Thermal-porosity characterization data of additively manufactured Ti-6Al-4V thin-walled structure via laser engineered net shaping

In-process thermal melt pool images and post-fabrication porosity labels are acquired for Ti-6Al-4V thin-walled structure fabricated with OPTOMEC Laser Engineered Net Shaping (LENS™) 750 system. The data is collected for nondestructive thermal characterization of direct laser deposition (DLD) build. More specifically, a Stratonics dual-wavelength pyrometer captures a top-down view of the melt pool of the deposition heat-affected zone (HAZ), which is above 1000 ∘ C , and Nikon X-Ray Computed Tomography (XCT) XT H225 captures internal porosity reflective of lack of fusion during the fabrication process. The pyrometer images provided in Comma Separated Values (CSV) format are cropped to center the melt pool to temperatures above 1000℃, indicative of the shape and distribution of temperature values. Melt pool coordinates are determined using pyrometer specifications and thin wall build parameters. XCT porosity labels of sizes between 0.05 mm to 1.00 mm are registered within 0.5 mm of the melt pool image coordinate. An XCT porosity-labeled table provided in the Excel spreadsheet format contains time stamps, melt pool coordinates, melt pool eccentricity, peak temperature, peak temperature coordinates, pore size, and pore label. Thermal-porosity data utilization aids in generating data-driven quality control models for manufacturing parts anomaly detection.

3D printed denture base material: The effect of incorporating TiO2 nanoparticles and artificial ageing on the physical and mechanical properties

OBJECTIVES

To evaluate the physical and mechanical properties of three-dimensional (3D) printed denture base resin incorporating TiO2 nanoparticles (NPs), subjected to a physical ageing process.

METHODS

Acrylic denture base samples were prepared by a Stereolithography (SLA) 3D printing technique reinforced with different concentrations (0.10, 0.25, 0.50, and 0.75) of silanated TiO2 NPs. The resulting nanocomposite materials were characterized in terms of degree of conversion (DC), and sorption/solubility flexural strength, impact strength, Vickers hardness and Martens hardness and compared with unmodified resin and conventional heat-cured (HC) material. The nanocomposites were reassessed after subjecting them to ageing in artificial saliva. A fractured surface was studied under a scanning electron microscope (SEM).

RESULTS

The addition of TiO2 NPs into 3D-printed resin significantly improved flexural strength/modulus, impact strength, Vickers hardness, and DC, while also slightly enhancing Martens hardness compared to the unmodified resin. Sorption values did not show any improvements, while solubility was reduced significantly. The addition of 0.10 wt% NPs provided the highest performance amongst the other concentrations, and 0.75 wt% NPs showed the lowest. Although ageing degraded the materials' performance to a certain extent, the trends remained the same. SEM images showed a homogenous distribution of the NPs at lower concentrations (0.10 and 0.25 wt%) but revealed agglomeration of the NPs with the higher concentrations (0.50 and 0.75 wt%).

SIGNIFICANCE

The outcomes of this study suggested that the incorporation of TiO2 NPs (0.10 wt%) into 3D-printed denture base material showed superior performance compared to the unmodified 3D-printed resin even after ageing in artificial saliva. The nanocomposite has the potential to extend service life of denture bases in future clinical use.

Clinical situations for which 3D Printing is considered an appropriate representation or extension of data contained in a medical imaging examination: vascular conditions

BACKGROUND

Medical three-dimensional (3D) printing has demonstrated utility and value in anatomic models for vascular conditions. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (3DPSIG) provides appropriateness recommendations for vascular 3D printing indications.

METHODS

A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with vascular indications. Each study was vetted by the authors and strength of evidence was assessed according to published appropriateness ratings.

RESULTS

Evidence-based recommendations for when 3D printing is appropriate are provided for the following areas: aneurysm, dissection, extremity vascular disease, other arterial diseases, acute venous thromboembolic disease, venous disorders, lymphedema, congenital vascular malformations, vascular trauma, vascular tumors, visceral vasculature for surgical planning, dialysis access, vascular research/development and modeling, and other vasculopathy. Recommendations are provided in accordance with strength of evidence of publications corresponding to each vascular condition combined with expert opinion from members of the 3DPSIG.

CONCLUSION

This consensus appropriateness ratings document, created by the members of the 3DPSIG, provides an updated reference for clinical standards of 3D printing for the care of patients with vascular conditions.

Poly(ɛ-caprolactone) and Eudragit E blends modulate the drug release profiles from FDM printlets

Thermoplastic polymers have been used to produce filaments by hot melt extrusion (HME), which can be applied to obtain 3D printlets by fused deposition modelling (FDM). Poly(ε-caprolactone) (PCL) is a low melting point thermoplastic polymer that provides HME filaments with excellent mechanical and printability properties. However, due to the highly hydrophobic properties of PCL, they afford printlets with slow drug release behaviour. We hypothesized that blending a less hydrophobic polymer, the Eudragit E (EudE), with PCL could be an approach to increase the drug release rate from PCL 3D printlets. PCL and EudE were blended at different proportions, 50:50, 60:40, 70:30, and 80:20 (w/w), to produce HME filaments. They were produced with dexamethasone at 5 % (w/w) and were effectively extruded and printable by FDM, except that composed of 50:50 (w/w). Printlets had homogeneous distribution of their components. Their drug release behaviour was dependent on the ratio of the polymeric blends. The highest EudE ratio (60:40 w/w) afforded printlets showing the highest release rate. Therefore, adding up to 40 % (w/w) of EudE to PCL does not impair the mechanical and printability properties of its HME filaments. This innovative approach is proposed here to modulate the drug release behaviour from PCL printlets.

A preliminary investigation of the subcutaneous tissue reaction to a 3D printed polydioxanone device in horses

BACKGROUND

A 3D printed self-locking device made of polydioxanone (PDO) was developed to facilitate a standardized ligation technique. The subcutaneous tissue reaction to the device was evaluated after implantation in ten horses of mixed age, sex and breed and compared to loops of poly(lactic-co-glycolic acid) (PLGA). In two of the horses, the implants were removed before closing the skin. The appearance of the implants and surrounding tissue was followed over time using ultrasonography. Implants were removed after 10 and 27 (± 1) days for histologic examination.

RESULTS

On macroscopic inspection at day 10, the PDO-device was fragmented and the surrounding tissue was oedematous. On ultrasonographic examination, the device was seen as a hyperechoic structure with strong acoustic shadowing that could be detected 4 months post-implantation, but not at 7 months. Histology revealed a transient granulomatous inflammation, i.e., a foreign body reaction, which surrounded both PDO and PLGA implants. The type and intensity of the inflammation varied between individuals and tissue category.

CONCLUSIONS

The 3D printed PDO-device caused a transient inflammatory reaction in the subcutaneous tissue and complete resorption occurred between 4 and 7 months. Considering the intended use as a ligation device the early fragmentation warrants further adjustments of both material and the 3D printing process before the device can be used in a clinical setting.

Characterization of mechanical stiffness using additive manufacturing and finite element analysis: potential tool for bone health assessment

BACKGROUND

Bone health and fracture risk are known to be correlated with stiffness. Both micro-finite element analysis (μFEA) and mechanical testing of additive manufactured phantoms are useful approaches for estimating mechanical properties of trabecular bone-like structures. However, it is unclear if measurements from the two approaches are consistent. The purpose of this work is to evaluate the agreement between stiffness measurements obtained from mechanical testing of additive manufactured trabecular bone phantoms and μFEA modeling. Agreement between the two methods would suggest 3D printing is a viable method for validation of μFEA modeling.

METHODS

A set of 20 lumbar vertebrae regions of interests were segmented and the corresponding trabecular bone phantoms were produced using selective laser sintering. The phantoms were mechanically tested in uniaxial compression to derive their stiffness values. The stiffness values were also derived from in silico simulation, where linear elastic μFEA was applied to simulate the same compression and boundary conditions. Bland-Altman analysis was used to evaluate agreement between the mechanical testing and μFEA simulation values. Additionally, we evaluated the fidelity of the 3D printed phantoms as well as the repeatability of the 3D printing and mechanical testing process.

RESULTS

We observed good agreement between the mechanically tested stiffness and μFEA stiffness, with R2 of 0.84 and normalized root mean square deviation of 8.1%. We demonstrate that the overall trabecular bone structures are printed in high fidelity (Dice score of 0.97 (95% CI, [0.96,0.98]) and that mechanical testing is repeatable (coefficient of variation less than 5% for stiffness values from testing of duplicated phantoms). However, we noticed some defects in the resin microstructure of the 3D printed phantoms, which may account for the discrepancy between the stiffness values from simulation and mechanical testing.

CONCLUSION

Overall, the level of agreement achieved between the mechanical stiffness and μFEA indicates that our μFEA methods may be acceptable for assessing bone mechanics of complex trabecular structures as part of an analysis of overall bone health.

Towards functionally individualised designed footwear recommendation for overuse injury prevention: a scoping review

Injury prevention is essential in running due to the risk of overuse injury development. Tailoring running shoes to individual needs may be a promising strategy to reduce this risk. Novel manufacturing processes allow the production of individualised running shoes that incorporate features that meet individual biomechanical and experiential needs. However, specific ways to individualise footwear to reduce injury risk are poorly understood. Therefore, this scoping review provides an overview of (1) footwear design features that have the potential for individualisation; and (2) the literature on the differential responses to footwear design features between selected groups of individuals. These purposes focus exclusively on reducing the risk of overuse injuries. We included studies in the English language on adults that analysed: (1) potential interaction effects between footwear design features and subgroups of runners or covariates (e.g., age, sex) for running-related biomechanical risk factors or injury incidences; (2) footwear comfort perception for a systematically modified footwear design feature. Most of the included articles (n = 107) analysed male runners. Female runners may be more susceptible to footwear-induced changes and overuse injury development; future research should target more heterogonous sampling. Several footwear design features (e.g., midsole characteristics, upper, outsole profile) show potential for individualisation. However, the literature addressing individualised footwear solutions and the potential to reduce biomechanical risk factors is limited. Future studies should leverage more extensive data collections considering relevant covariates and subgroups while systematically modifying isolated footwear design features to inform footwear individualisation.

Preliminary exploration of the biomechanical properties of three novel cervical porous fusion cages using a finite element study

BACKGROUND

Porous cages are considered a promising alternative to high-density cages because their interconnectivity favours bony ingrowth and appropriate stiffness tuning reduces stress shielding and the risk of cage subsidence.

METHODS

This study proposes three approaches that combine macroscopic topology optimization and micropore design to establish three new types of porous cages by integrating lattices (gyroid, Schwarz, body-centred cubic) with the optimized cage frame. Using these three porous cages along with traditional high-density cages, four ACDF surgical models were developed to compare the mechanical properties of facet articular cartilage, discs, cortical bone, and cages under specific loads.

RESULTS

The facet joints in the porous cage groups had lower contact forces than those in the high-density cage group. The intervertebral discs in all models experienced maximum stress at the C5/6 segment. The stress distribution on the cortical bone surface was more uniform in the porous cage groups, leading to increased average stress values. The gyroid, Schwarz, and BCC cage groups showed higher average stress on the C5 cortical bone. The average stress on the surface of porous cages was higher than that on the surface of high-density cages, with the greatest difference observed under the lateral bending condition. The BCC cage demonstrated favourable mechanical stability.

CONCLUSION

The new porous cervical cages satifies requirements of low rigidity and serve as a favourable biological scaffold for bone ingrowth. This study provides valuable insights for the development of next-generation orthopaedic medical devices.

Improving the performance and versatility of microfluidic thread electroanalytical devices by automated injection with electronic pipettes: a new and powerful 3D-printed analytical platform

Microfluidic cotton thread-based electroanalytical devices (μTEDs) are analytical systems with attractive features such as spontaneous passive flow, low cost, minimal waste production, and good sensitivity. Currently, sample injection in µTEDs is performed by hand using manual micropipettes, which have drawbacks such as inconstant speed and position, dependence of skilled analysts, and need of physical effort of operator during prolonged times, leading to poor reproducibility and risk of strain injury. As an alternative to these inconveniences, we propose, for the first time, the use of electronic micropipettes to carry out automated injections in µTEDs. This new approach avoids all disadvantages of manual injections, while also improving the performance, experience, and versatility of µTEDs. The platform developed here is composed by three 3D-printed electrodes (detector) attached to a 3D-printed platform containing an adjustable holder that keeps the electronic pipette in the same x/y/z position. As a proof-of-concept, both injection modes (manual and electronic) were compared using three model analytes (nitrite, paracetamol, and 5-hydroxytryptophan) on µTED with amperometric detection. As result, improved analytical performance (limits of detection between 2.5- and 5-fold lower) was obtained when using electronic injections, as well as better repeatability/reproducibility and higher analytical frequencies. In addition, the determination of paracetamol in urine samples suggested better precision and accuracy for automated injection. Thus, electronic injection is a great advance and changes the state-of-art of µTEDs, mainly considering the use of more modern and versatile electronic pipettes (wider range of pre-programmed modes), which can lead to the development of even more automated systems.

Synergistic sono-adsorption and adsorption-enhanced sonochemical degradation of dyes in water by additive manufactured PVDF-based materials

The present study proposes the first mechanistic model accounting for the most meaningful physico-chemical phenomena taking place in liquid phase adsorption processes under ultrasound. Initially, this study was aimed at developing an easy-to-make and easy-to-recover piezocatalyst for the degradation of RhB in water by combining the high piezocatalytical performance of BaTiO3 with a compatible piezoelectric support such as PVDF, manufactured by a customised additive manufacturing - direct ink writing system with in-situ poling. However, initial results showed that the resulting PVDF-BaTiO3 composite slabs performed worse than BaTiO3 piezocatalysts on their own, and that poling did not have any effect on their performance (82% RhB removal after 2 h when using either poled or unpoled PVDF-BaTiO3 composite slabs compared to 92% RhB removal after 2 h in presence of BaTiO3 piezocatalysts). Further investigation with pure PVDF materials demonstrated that, instead of piezocatalysis, synergistic ultrasound-assisted adsorption and sonochemical degradation were taking place, enabling the removal of >95% of the dye within 40 min of ultrasound treatment in the presence of 4 g L-1 of additive manufactured PVDF slabs. The results of this study and their evaluation with the mechanistic model proposed for liquid phase adsorption under ultrasound suggest that the adsorption of RhB on additive manufactured PVDF slabs was enhanced by the structure, higher specific surface ratio and higher volume of mesopores achieved through the 3D-printing process, as well as the minimisation of film resistance to mass transport due to ultrasound. Moreover, adsorption on additive manufactured PVDF enhanced the sonochemical degradation of the dye due to its high concentration in the adsorbed phase. This study demonstrates that adsorption processes, especially in the presence of PVDF materials, may be significantly more important in piezocatalysis than what has been reported to date, to the point that the synergistic combination of sono-adsorption and sonochemical degradation in presence of additive-manufactured PVDF slabs may be enough to achieve high removal rates of dyes in water.

3D printed indirect bonding trays: Transfer accuracy of hard versus soft resin material in a prospective, randomized, single-blinded clinical study

OBJECTIVES

This prospective clinical study aimed to compare transfer accuracy and immediate loss rate of hard versus soft transfer trays utilizing a CAD/CAM workflow.

METHODS

We performed virtual bracket placement on intraoral scans of adolescent patients to create individual indirect bonding trays. Orthodontic software (Appliance Designer, 3Shape, Copenhagen, Denmark) was used to design the trays, which were then produced using 3D printing technology. Patients were randomly assigned to the hard or soft resin groups with a 1:1 allocation. Subgroups were determined based on the Little's Irregularity Index and distributed equally.

RESULTS

552 brackets were bonded onto adolescent patients using 46 CAD/CAM indirect bonding trays. The linear mean transfer errors ranged from -0.011 mm (soft) to -0.162 mm (hard) and angularly -0.255° (hard) and -0.243° (soft). No statistically significant differences were found between the subgroups or soft and hard resin groups. However, the transfer accuracy of molar brackets was significantly lower in the transversal and horizontal directions. All mean transfer errors were within the limits of clinical acceptability. The loss rate was 2.4 % in the hard resin group and 2.3 % in the soft resin group. The Intra Observer Correlation was excellent.

SIGNIFICANCE

CAD/CAM technology for indirect bracket bonding has been proven reliable in a randomized clinical trial. Both hard and soft resin showed a low rate of immediate loss compared to the current literature. Soft resin was more favorable than hard resin in terms of accuracy and usability. However, the indirect bonding of molar brackets is significantly less accurate than incisor brackets.

A Systematic Analysis of Additive Manufacturing Techniques in the Bioengineering of In Vitro Cardiovascular Models

Additive Manufacturing is noted for ease of product customization and short production run cost-effectiveness. As our global population approaches 8 billion, additive manufacturing has a future in maintaining and improving average human life expectancy for the same reasons that it has advantaged general manufacturing. In recent years, additive manufacturing has been applied to tissue engineering, regenerative medicine, and drug delivery. Additive Manufacturing combined with tissue engineering and biocompatibility studies offers future opportunities for various complex cardiovascular implants and surgeries. This paper is a comprehensive overview of current technological advancements in additive manufacturing with potential for cardiovascular application. The current limitations and prospects of the technology for cardiovascular applications are explored and evaluated.

Quintessential commence of three-dimensional printing in periodontal regeneration-A review

The prime focus of regenerative periodontal therapy is to reconstruct or regenerate the lost periodontium, including both hard and soft tissues. Over the years, periodontics has witnessed different regenerative modalities, such as bone grafts, guided tissue membranes, growth factors, stem cell technology, 3D printing, etc. 3D printing is a newly emerging manufacturing technology that finds applications in diverse fields, including aerospace, defense, art and design, medical and dental field. Originally developed for non-biological applications, 3D printing has undergone modifications to print biocompatible materials and living cells to minimize any potential compromise on cell viability. Thus, the utilisation of 3D printing in the regeneration of lost periodontal tissues represents a novel approach that facilitates optimal cell interactions and promotes the successful regeneration of biological tissues.

Atorvastatin liposomes in a 3D-printed polymer film: a repurposing approach for local treatment of oral candidiasis

Oral candidiasis (OC) is an opportunistic fungal infection, common amongst the elderly and the immunocompromised. Unfortunately, the therapeutic efficacy of common antifungals is imperiled by the rise of antifungal drug resistance. An alternative promising therapeutic option possibly contributing to antifungal therapy is drug repurposing. Herein, we aimed to employ novel pharmaceutical drug delivery for enhancing the emerging antifungal potential of the hypocholesterolemic drug atorvastatin (ATV). ATV-propylene-glycol-liposomes (ATV/PG-Lip) were prepared then integrated in 3D-printed (3DP) mucoadhesive films comprising chitosan, polyvinyl-alcohol and hydroxypropyl methylcellulose, as an innovative blend, for the management of OC. ATV/PG-Lip demonstrated good colloidal properties of particle size (223.3 ± 2.1 nm), PDI (0.12 ± 0.001) and zeta potential (-18.2 ± 0.3 mV) with high entrapment efficiency (81.15 ± 1.88%) and sustained drug release. Also, ATV/PG-Lip showed acceptable three-month colloidal stability and in vitro cytocompatibility on human gingival fibroblasts. The developed 3DP-films exhibited controlled ATV release (79.4 ± 1.4% over 24 h), reasonable swelling and mucoadhesion (2388.4 ± 18.4 dyne/cm2). In vitro antifungal activity of ATV/PG-Lip was confirmed against fluconazole-resistant Candida albicans via minimum inhibitory concentration determination, time-dependent antifungal activity, agar diffusion and scanning electron microscopy. Further, ATV/PG-Lip@3DP-film exceeded ATV@3DP-film in amelioration of infection and associated inflammation in an in vivo oral candidiasis rabbit model. Accordingly, the results confirm the superiority of the fabricated ATV/PG-Lip@3DP-film for the management of oral candidiasis and tackling antifungal resistance.

Optimize the pore size-pore distribution-pore geometry-porosity of 3D-printed porous tantalum to obtain optimal critical bone defect repair capability

The treatment and reconstruction of large or critical size bone defects is a challenging clinical problem. Additive manufacturing breaks the technical difficulties of preparing complex conformation and anatomically matched personalized porous tantalum implants, but the ideal pore structure for 3D-printed porous tantalum in critical bone defect repair applications remains unclear. Guiding appropriate bone tissue regeneration by regulating proper pore size-pore distribution-pore geometry-porosity is a challenge for its fabrication and application. We fabricated porous tantalum (PTa) scaffolds with six different combinations of pore structures using powder bed laser melting (L-PBF) technology. In vitro biological experiments were conducted to systematically investigate the effects of pore structure characteristics on osteoblast behaviors, showing that the bionic trabecular structure with both large and small poress facilitated cell permeation, proliferation and differentiation compared to the cubic structure with uniform pore sizes. The osteogenesis of PTa with different porosity of trabecular structures was further investigated by a rabbit condyle critical bone defect model. Synthetically, T70% up-regulated the expression of osteogenesis-related genes (ALP, COLI, OCN, RUNX-2) and showed the highest bone ingrowth area and bone contact rate in vivo after 16 weeks, with the best potential for critical bone defect repair. Our results suggested that the bionic trabecular structure with a pore size distribution of 200-1200 μm, an average pore size of 700 μm, and a porosity of 70 % is the best choice for repairing critical bone defects, which is expected to guide the clinical application of clinical 3D-printed PTa scaffolds.

Understanding of trabecular-cortical transition zone: Numerical and experimental assessment of multi-morphology scaffolds

Applications of additive manufacturing (AM) in tissue engineering develop rapidly. AM offers layer-by-layer creation of complex objects, developed to restore functionality of, or replace, damaged tissues. Porous 3D-printed functional gradient structures are of particular interest: their special architecture makes it possible to simulate the heterogeneity of the replaced tissue and, by continuously changing the mechanical properties, to avoid the concentration of stresses that can be caused by abrupt geometric changes. Such structures also allow combinations of different types of unit cells and a smooth transition between them, making design of personalised scaffolds with optimal parameters for the replacement of damaged host tissue at the interface between tissues possible. This paper presents the results of development of scaffold structures with gradients of porosity and multi-morphology using unit cells based on triply periodic minimal surfaces (TPMS). The mechanical behaviour of additively manufactured scaffold prototypes made of polylactide acid (PLA) was studied under compressive loading. Strain fields on their surface were captured using the Vic-3d Micro-DIC digital image correlation system and compared with those obtained with detailed numerical simulations, employing elastic-plastic properties of PLA, obtained in experiments. The effect of gradient parameters and unit-cell morphology on the stress distribution in scaffolds was analysed. A smooth gradient transition between cells with different morphologies was found to reduce the probability of structural failure under intense compressive loading. A good agreement between numerical results and experimental data was achieved, which justifies application of the developed approach to design of personalised bone scaffolds.

Intelligent Vascularized 3D/4D/5D/6D-Printed Tissue Scaffolds

Blood vessels are essential for nutrient and oxygen delivery and waste removal. Scaffold-repairing materials with functional vascular networks are widely used in bone tissue engineering. Additive manufacturing is a manufacturing technology that creates three-dimensional solids by stacking substances layer by layer, mainly including but not limited to 3D printing, but also 4D printing, 5D printing and 6D printing. It can be effectively combined with vascularization to meet the needs of vascularized tissue scaffolds by precisely tuning the mechanical structure and biological properties of smart vascular scaffolds. Herein, the development of neovascularization to vascularization to bone tissue engineering is systematically discussed in terms of the importance of vascularization to the tissue. Additionally, the research progress and future prospects of vascularized 3D printed scaffold materials are highlighted and presented in four categories: functional vascularized 3D printed scaffolds, cell-based vascularized 3D printed scaffolds, vascularized 3D printed scaffolds loaded with specific carriers and bionic vascularized 3D printed scaffolds. Finally, a brief review of vascularized additive manufacturing-tissue scaffolds in related tissues such as the vascular tissue engineering, cardiovascular system, skeletal muscle, soft tissue and a discussion of the challenges and development efforts leading to significant advances in intelligent vascularized tissue regeneration is presented.

Cost-effective 3D scanning and printing technologies for outer ear reconstruction: current status

Current 3D scanning and printing technologies offer not only state-of-the-art developments in the field of medical imaging and bio-engineering, but also cost and time effective solutions for surgical reconstruction procedures. Besides tissue engineering, where living cells are used, bio-compatible polymers or synthetic resin can be applied. The combination of 3D handheld scanning devices or volumetric imaging, (open-source) image processing packages, and 3D printers form a complete workflow chain that is capable of effective rapid prototyping of outer ear replicas. This paper reviews current possibilities and latest use cases for 3D-scanning, data processing and printing of outer ear replicas with a focus on low-cost solutions for rehabilitation engineering.

Investigating the availability of 3D-printed firearm designs on the clear web

The release of the plans of the 3D-printed Liberator firearm sparked a wave of new designs from creators worldwide, resulting in an extensive collection of 3D-printed firearm plans, in particular blueprints, and parts available for almost unrestricted download on the internet. Identifying and categorizing the diverse range of 3D-printed firearms and components pose a challenge due to the abundance of designs available. Between 2021 and April 2023, data was collected on over 2,100 3D-printed firearm plans. While blueprints of fully 3D-printed firearms initially dominated the scene, hybrid designs and parts kit completions / conversions (PKC) have gained popularity for their improved reliability and performance. The now highly networked community offers considerable support with detailed instructions and procedures, providing precise guidance for construction. This systematic classification, grouping and structuration of the recorded data on the Clear Web supported the identification of patterns of the main threat trends related to 3D-printed firearms.

Hydroxyapatite 3D-printed scaffolds with Gyroid-Triply periodic minimal surface porous structure: Fabrication and an in vivo pilot study in sheep

Bone repair is a major challenge in regenerative medicine, e.g. for large defects. There is a need for bioactive, highly percolating bone substitutes favoring bone ingrowth and tissue healing. Here, a modern 3D printing approach (VAT photopolymerization) was exploited to fabricate hydroxyapatite (HA) scaffolds with a Gyroid-"Triply periodic minimal surface" (TPMS) porous structure (65% porosity, 90.5% HA densification) inspired from trabecular bone. Percolation and absorption capacities were analyzed in gaseous and liquid conditions. Mechanical properties relevant to guided bone regeneration in non-load bearing sites, as for maxillofacial contour reconstruction, were evidenced from 3-point bending tests and macrospherical indentation. Scaffolds were implanted in a clinically-relevant large animal model (sheep femur), over 6 months, enabling thorough analyses at short (4 weeks) and long (26 weeks) time points. In vivo performances were systematically compared to the bovine bone-derived Bio-OssⓇ standard. The local tissue response was examined thoroughly by semi-quantitative histopathology. Results demonstrated the absence of toxicity. Bone healing was assessed by bone dynamics analysis through epifluorescence using various fluorochromes and quantitative histomorphometry. Performant bone regeneration was evidenced with similar overall performances to the control, although the Gyroid biomaterial slightly outperformed Bio-OssⓇ at early healing time in terms of osteointegration and appositional mineralization. This work is considered a pilot study on the in vivo evaluation of TPMS-based 3D porous scaffolds in a large animal model, for an extended period of time, and in comparison to a clinical standard. Our results confirm the relevance of such scaffolds for bone regeneration in view of clinical practice. STATEMENT OF SIGNIFICANCE: Bone repair, e.g. for large bone defects or patients with defective vascularization is still a major challenge. Highly percolating TPMS porous structures have recently emerged, but no in vivo data were reported on a large animal model of clinical relevance and comparing to an international standard. Here, we fabricated TPMS scaffolds of HA, determined their chemical, percolation and mechanical features, and ran an in-depth pilot study in the sheep with a systematic comparison to the Bio-OssⓇ reference. Our results clearly show the high bone-forming capability of such scaffolds, with outcomes even better than Bio-OssⓇ at short implantation time. This preclinical work provides quantitative data validating the relevance of such TMPS porous scaffolds for bone regeneration in view of clinical evaluation.

Multimodal additive manufacturing of biomimetic tympanic membrane replacements with near tissue-like acousto-mechanical and biological properties

The three additive manufacturing techniques fused deposition modeling, gel plotting and melt electrowriting were combined to develop a mimicry of the tympanic membrane (TM) to tackle large TM perforations caused by chronic otitis media. The mimicry of the collagen fiber orientation of the TM was accompanied by a study of multiple funnel-shaped mimics of the TM morphology, resulting in mechanical and acoustic properties similar to those of the eardrum. For the different 3D printing techniques used, the process parameters were optimized to allow reasonable microfiber arrangements within the melt electrowriting setup. Interestingly, the fiber pattern was less important for the acousto-mechanical properties than the overall morphology. Furthermore, the behavior of keratinocytes and fibroblasts is crucial for the repair of the TM, and an in vitro study showed a high biocompatibility of both primary cell types while mimicking the respective cell layers of the TM. A simulation of the in vivo ingrowth of both cell types resulted in a cell growth orientation similar to the original collagen fiber orientation of the TM. Overall, the combined approach showed all the necessary parameters to support the growth of a neo-epithelial layer with a similar structure and morphology to the original membrane. It therefore offers a suitable alternative to autologous materials for the treatment of chronic otitis media. STATEMENT OF SIGNIFICANCE: Millions of people worldwide suffer from chronic middle ear infections. Although the tympanic membrane (TM) can be reconstructed with autologous materials, the grafts used for this purpose require extensive manual preparation during surgery. This affects not only the hearing ability but also the stability of the reconstructed TM, especially in the case of full TM reconstruction. The synthetic alternative presented here mimicked not only the fibrous structure of the TM but also its morphology, resulting in similar acousto-mechanical properties. Furthermore, its high biocompatibility supported the migration of keratinocytes and fibroblasts to form a neo-epithelial layer. Overall, this completely new TM replacement was achieved by combining three different additive manufacturing processes.

A comparison of droplet deposition modelling, fused filament fabrication, and injection moulding for the production of oral dosage forms containing hydrochlorothiazide

Additive manufacturing (AM) possesses a transformative potential to revolutionize personalized medicine fabrication. Fused filament fabrication (FFF), an advanced AM technique, enables the development of tailored medicines with customizable dosages and controlled release properties. Nevertheless, filament prerequisites impose material limitations and present considerable challenges, necessitating a comprehensive evaluation of mechanical, rheological, and thermal characteristics to circumvent complications during the FFF process. Droplet deposition modeling (DDM), an innovative AM approach derived from injection molding (IM) technology, processes granulate feedstock to facilitate the production of personalized medicines. This study delves into the effects of FFF, DDM, and IM techniques on the release profiles of Hydrochlorothiazide, a widely employed drug for hypertension and edema treatment. By varying infill density, the investigation assesses the manufactured tablets using DDM and FFF methods. Our findings show that tablets made with FFF and DDM with identical infill densities had distinct microstructures, resulting in variable drug release profiles. Decreasing the infill densities resulted in higher sample porosity, leading to an accelerated drug release rate. A comparative analysis of drug release profiles from DDM and IM fabricated tablets demonstrated notable differences, despite DDM's origins in injection molding technology. This comprehensive study underscores the significance of not only infill densities but also the choice of manufacturing technique, as both factors can profoundly influence drug release profiles. By shedding light on these considerations, the research contributes to the ongoing advancement of personalized medicine through additive manufacturing technologies.

Effects of layer thickness and build angle on the microbial adhesion of denture base polymers manufactured by digital light processing

PURPOSE

To investigate the effects of printing-layer thickness and build angle on the surface characteristics and microbial adhesion of denture base polymers manufactured by digital light processing (DLP).

METHODS

Specimens were additively manufactured using DLP. The specimens were printed with different printing-layer thicknesses (25, 50, and 100 μm) and build angles (0°, 45°, and 90°). Scanning electron microscopy was used to observe the surface topography, and the arithmetical mean heights (Sa) were measured. Moreover, the initial Candida albicans (C. albicans) adhesion to the specimens was evaluated using an adhesion test. Finally, two-way ANOVA and Tukey's multiple comparison tests were conducted.

RESULTS

The results regarding the Sa values exhibited a statistically significant interaction (F (4, 45) = 90.77, P < 0.0001). The build angle has a significant impact on the surface topography. Furthermore, quantitative results revealed that the printing-layer thickness significantly affected C. albicans adhesion (F (2, 99) = 6.96, P = 0.0015).

CONCLUSIONS

The surface roughness was significantly affected by the printing-layer thickness and the build angle. Additionally, the surface topography was mainly determined by the build angle. Furthermore, the adhesion of C. albicans to the DLP-printed denture surfaces was significantly affected by the printing-layer thickness but not by the build angle. Consequently, it is critical to decrease the thickness of the printing layer to produce digital dentures with optimal material properties.

Comparison of the fatigue life of pure titanium and titanium alloy clasps manufactured by laser powder bed fusion and its prediction before manufacturing

PURPOSE

In this study, the fatigue properties of additively manufactured titanium clasps were compared with those of commercially pure titanium (CPTi) and Ti-6Al-4V (Ti64), manufactured using laser powder-bed fusion.

METHODS

Fourteen specimens of each material were tested under the cyclic condition at 1 Hz with applied maximum strokes ranging from 0.2 to 0.5 mm, using a small stroke fatigue testing machine. A numerical approach using finite element analysis (FEA) was also developed to predict the fatigue life of the clasps.

RESULTS

The results showed that although no significant differences were observed between the two materials when a stroke larger than 0.35 mm was applied, CPTi had a better fatigue life under a stroke smaller than 0.33 mm. The distributions of the maximum principal stress in the FEA and the fractured position in the experiment were in good agreement.

CONCLUSIONS

Using a design of the clasp of the present study, the advantage of the CPTi clasp in its fatigue life under a stroke smaller than 0.33 mm was revealed experimentally. Furthermore, the numerical approach using FEA employing calibrated parameters for the Smith-Watson-Topper method are presented. Under the limitations of the aforementioned clasp design, the establishment of a numerical method enabled us to predict the fatigue life and ensure the quality of the design phase before manufacturing.

Multifunctional polydopamine - Zn2+-curcumin coated additively manufactured ceramic bone grafts with enhanced biological properties

The lack of site-specific chemotherapeutic agents after osteosarcoma surgeries often induces severe side effects. We propose the utilization of curcumin as an alternative natural chemo-preventive drug for tumor-specific delivery systems with 3D printed tricalcium phosphate (TCP) based artificial bone grafts. The poor bioavailability and hydrophobic nature of curcumin restrict its clinical use. We have used polydopamine (PDA) coating with Zn2+ functionalization to enhance the curcumin release in the biological medium. The obtained PDA-Zn2+ complex is characterized by X-ray photoelectron spectroscopy (XPS). The presence of PDA-Zn2+ coating leads to ~2 times enhancement in curcumin release. We have computationally predicted and validated the optimized surface composition by a novel multi-objective optimization method. The experimental validation of the predicted compositions indicates that the PDA-Zn2+ coated curcumin immobilized delivery system leads to a ~12 folds decrease in osteosarcoma viability on day 11 as compared to only TCP. The osteoblast viability shows ~1.4 folds enhancement. The designed surface shows the highest ~90 % antibacterial efficacy against gram-positive and gram-negative bacteria. This unique strategy of curcumin delivery with PDA-Zn2+ coating is expected to find application in low-load bearing critical-sized tumor-resection sites.

Additive manufacture of PLLA scaffolds reinforced with graphene oxide nano-particles via digital light processing (DLP)

In this study, 3D printing of poly-l-lactic acid (PLLA) scaffolds reinforced with graphene oxide (GO) nanoparticles via Digital Light Processing (DLP) was investigated to mimic bone tissue. Stereolithography is one of the most accurate additive manufacturing methods, but the dominant available materials used in this method are toxic. In this research, a biocompatible resin (PLLA) was synthetized and functionalized to serve the purpose. Due to the low mechanical properties of the printed product with the neat resin, graphene oxide nanoparticles in three levels (0.5, 1, and 1.5 wt%) were added with the aim of enhancing the mechanical properties. At first, the optimum post cure time of the neat resin was investigated. Consequently, all the parts were post-cured for 3 h after printing. Due to the temperature-dependent structure of GO, all samples were placed in an oven at 85°C for different time periods of 0, 6, 12, and 18 h to increase mechanical properties. The compression test of heat-treated samples reveals that the compressive strength of the printed parts containing 0.5,1, and 1.5% of GO increased by 151,162 ad 235%, respectively. Scaffolds with the designed pore sizes of 750 microns and a porosity of 40% were printed. Surface hydrophilicity test was performed for all samples showing that the hydrophilicity of the samples increased with increasing GO percentage. The degradation behavior of the samples was evaluated in a PBS environment, and it revealed that by increasing GO, the rate of component degradation increased, but the heat treatment had the opposite effect and decreased the degradation rate. Finally, besides improving biological properties, a significant increase in mechanical properties under compression can introduce the printed scaffolds as a suitable option for bone implants.

Laser texturing of additively manufactured implants: A tool to programme biological response

The advent of additive manufacturing (AM) is rapidly shaping healthcare technologies pushing forward personalisation and enhanced implant functionalisation to improve clinical outcomes. AM techniques such as powder bed fusion (PBF) have been adopted despite the need to modify the as-built surface post manufacture. Medical device manufacturers have focused their efforts on refining various physical and chemical surface finishing approaches, however there is little consensus and some methods risk geometry alteration or contamination. This has led to a growing interest in laser texturing technologies to engineer the device surface. Herein, several bioinspired micro and nano textures were applied to laser PBF Ti-6Al-V4 substrates to alter physicochemical properties and in-turn we sought to understand what influences these alterations had on a human osteosarcoma cell line (MG63). Significant variations in roughness and time dependent contact angles were revealed between different patterns provide a tool to elicit desired biological responses. All surface treatments effectively enhanced early cell behaviour and in particular coverage was increased for the micro-textures. Influence of the patterns on cell differentiation was less consistent with alkaline phosphatase content increased only for the channel, grid and dual textures. While long term (21 days) mineralisation was found to be significantly enhanced in grids, dual, triangles and shark skin textures. Further regression analysis of all physicochemical and biological variables indicated that several properties should be used to strongly correlate cell behaviour, resulting in 82 % of the 21 day mineralisation dataset explained through a combination of roughness kurtosis and glycerol contact angle. Overall, this manuscript demonstrates the ability of laser texturing to offer tailored cell-surface interactions, which can be tuned to offer a tool to drive functional customisation of anatomically customised medical devices.

The effect of pore size on the mechanical properties, biodegradation and osteogenic effects of additively manufactured magnesium scaffolds after high temperature oxidation: An in vitro and in vivo study

The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 μm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.

Design of customized implants and 3D printing of symmetric and asymmetric cranial cavities

A methodology has been developed in this work to design customized cranial implants from computed tomography (CT) scan images for symmetric as well as asymmetric defects. The two-dimensional CT scan images were converted into three-dimensional geometric models using software packages. Two cases of cranial cavities at different locations were considered for implant design using two different approaches. Case 1 is having a symmetric cranial cavity while Case 2 has an asymmetric frontal cranial cavity. The craniums with defects were 3D reconstructed. Customized cranial implants were made for the two cases. In Case 1, symmetry was used to design the cranial implant. Symmetry cannot be used in Case 2. In Case 2, the implant was designed by blending from the surface available adjacent to the missing portion of the cranium. 3D reconstructed bone models and customized implants were 3D printed in poly-lactic acid (PLA) using a fused deposition modeling process for form and fit evaluation. Finite element analysis was performed to compare the mechanical behavior of bone, and the two biomaterials - polyether ether ketone (PEEK), and Ti6Al4V. Static structural finite element analysis was performed to simulate the impact of falling off a bicycle with an impact on the cranial implants in the two cases. The load was modeled as a normal force acting on the surface of the implant. It was found that the stresses in the titanium alloy are comparable to those of PEEK for both the cases. However, the strains and deformation were found to be much smaller compared to those in PEEK. Therefore, the titanium alloy is the material of choice for both the cases among the materials under consideration. The designed implants are solid hence may face the challenge in bone ingrowth. In future studies, the implant can be made porous by incorporating a lattice structure to enhance osseointegration and promote bone ingrowth. Implants for both symmetric and asymmetric defect cases in cranium were successfully designed.

3D-printed biosurfactant-chitosan antibacterial coating for the prevention of silicone-based associated infections

Infections associated with the surfaces of medical devices represent a critical problem due to biofilm formation and the growing resistance towards antibacterial drugs. This is particularly relevant in commonly used invasive devices such as silicone-based ones where a demand for alternative antibiofilm surfaces is increasing. In this work, an antimicrobial chitosan-biosurfactant hydrogel mesh was produced by 3D-printing. The 3D structure was designed to coat polydimethylsiloxane-based medical devices for infection prevention. Additionally, the porous 3D structure allows the incorporation of customized bioactive components. For this purpose, two biosurfactants (surfactin and sophorolipids) were biosynthesized and tested for their antimicrobial activity. In addition, the printing of surfactant-chitosan-based coatings was optimized, and the resulting 3D structures were characterized (i.e., wettability, FTIR-ATR, antimicrobial activity, and biocompatibility). Compared with surfactin, the results showed a better yield and higher antibacterial activity against Gram-positive bacteria for sophorolipids (SLs). Thus, SLs were used to produce chitosan-based 3D-printed coatings. Overall, the SLs-impregnated coatings showed the best antibacterial activity against Staphylococcus aureus planktonic bacteria (61 % of growth inhibition) and antibiofilm activity (2 log units reduction) when compared to control. Furthermore, concerning biocompatibility, the coatings were cytocompatible towards human dermal fibroblasts. Finally, the coating presented a mesh suitable to be filled with a model bioactive compound (i.e., hyaluronic acid), paving the way to be used for customized therapeutics.

Formability of curved multilayer laminates via 3D printing using twisted continuous fiber composites

3D printers can print free-form 3D shapes; however, their mechanical properties are unsatisfactory. 3D printers can print 3D shapes freely but the resulting products exhibit unsatisfactory mechanical properties. 3D printing using CFRTP enables the formation of 3D structures with improved mechanical properties. When molding a structure with curved parts using a continuous carbon-fiber-reinforced thermoplastic (CFRTP) 3D printer, the difference in the inner and outer paths of the filament width during arc printing causes the CFRTP filament to become twisted, resulting in poor molding accuracy. In this study, we evaluated the formability of laminates via 3D printing with twisted CFRTP filaments to reduce the inner and outer path differences. And the maximum change in the filament width, which is defined as the maximum width minus the minimum width in one round of fibers, was defined as the forming accuracy. In the case of single-layer printing, the filament width decreased as the twist angle increased, and the forming accuracy (variation in the filament width) decreased. However, when stacking multiple layers, the maximum change in the filament width was the least when the twist angle was 6°. The discovery of the optimum twist angle at 1 K is the most significant aspect of this study and indicates the possibility of an optimum twist angle for various values of K.

Physiomimetic biocompatibility evaluation of directly printed degradable porous iron implants using various cell types

Additively manufactured (AM) degradable porous metallic biomaterials offer unique opportunities for satisfying the design requirements of an ideal bone substitute. Among the currently available biodegradable metals, iron has the highest elastic modulus, meaning that it would benefit the most from porous design. Given the successful preclinical applications of such biomaterials for the treatment of cardiovascular diseases, the moderate compatibility of AM porous iron with osteoblast-like cells, reported in earlier studies, has been surprising. This may be because, as opposed to static in vitro conditions, the biodegradation products of iron in vivo are transported away and excreted. To better mimic the in situ situations of biodegradable biomaterials after implantation, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static conditions to the conditions with dynamic in situ-like fluid flow perfusion in a bioreactor. Furthermore, the compatibility of these scaffolds with four different cell types was evaluated to better understand the implications of these implants for the complex process of natural wound healing. These included endothelial cells, L929 fibroblasts, RAW264.7 macrophage-like cells, and osteoblastic MG-63 cells. The biodegradation rate of the scaffolds was significantly increased in the perfusion bioreactor as compared to static immersion. Under either condition, the compatibility with L929 cells was the best. Moreover, the compatibility with all the cell types was much enhanced under physiomimetic dynamic flow conditions as compared to static biodegradation. Our study highlights the importance of physiomimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro. STATEMENT OF SIGNIFICANCE: Additively manufactured (AM) degradable porous metals offer unique opportunities for the treatment of large bony defects. Despite the successful preclinical applications of biodegradable iron in the cardiovascular field, the moderate compatibility of AM porous iron with osteoblast-like cells was reported. To better mimic the in vivo condition, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static condition to dynamic perfusion. Furthermore, the compatibility of these scaffolds with various cell types was evaluated to better simulate the process of natural wound healing. Our study suggests that AM porous iron holds great promise for orthopedic applications, while also highlighting the importance of physio-mimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro.

Fatigue behavior of additively manufactured Ti3Al2V alloy

This study measured the tensile, compression, and fatigue behavior of additively manufactured Ti3Al2V as a function of build orientation. Ti3Al2V alloy was prepared by mixing commercially pure titanium (CpTi) and Ti6Al4V in 1:1 wt. ratio. Laser powder bed fusion (L-PBF) based additive manufacturing (AM) technique was used to fabricate the samples. Tensile tests resulted in an ultimate strength of 989 ± 8 MPa for Ti3Al2V. Ti6Al4V 90° orientation samples showed a compressive yield strength of 1178 ± 33 MPa, and that for Ti3Al2V 90° orientation was 968 ± 24 MPa. Varying the build orientation to account for anisotropy, Ti32-45° and Ti32-0° displayed similar compressive yield strength values of 1071 ± 16 and 1051± 18 MPa, respectively, higher than Ti32-90°. Fatigue loading revealed an endurance limit (10 million cycles) of 250 MPa for Ti6Al4V and 219 MPa for Ti3Al2V built at 90° orientations. The effect of the build orientation was significant under fatigue loading; Ti3Al2V built at 45° displayed an endurance limit of 387.5 MPa, and 0° showed 512 MPa; more than two-fold increment in endurance limit was observed. Our results show the potential of Ti3Al2V alloy for orthopedic devices, replacing Ti6Al4V alloy, particularly in load-bearing applications.

Medical 3D printing with polyjet technology: effect of material type and printing orientation on printability, surface structure and cytotoxicity

Due to its high printing resolution and ability to print multiple materials simultaneously, inkjet technology has found wide application in medicine. However, the biological safety of 3D-printed objects is not always guaranteed due to residues of uncured resins or support materials and must therefore be verified. The aim of this study was to evaluate the quality of standard assessment methods for determining the quality and properties of polyjet-printed scaffolds in terms of their dimensional accuracy, surface topography, and cytotoxic potential.Standardized 3D-printed samples were produced in two printing orientations (horizontal or vertical). Printing accuracy and surface roughness was assessed by size measurements, VR-5200 3D optical profilometer dimensional analysis, and scanning electron microscopy. Cytotoxicity tests were performed with a representative cell line (L929) in a comparative laboratory study. Individual experiments were performed with primary cells from clinically relevant tissues and with a Toxdent cytotoxicity assay.Dimensional measurements of printed discs indicated high print accuracy and reproducibility. Print accuracy was highest when specimens were printed in horizontal direction. In all cytotoxicity tests, the estimated mean cell viability was well above 70% (p < 0.0001) regardless of material and printing direction, confirming the low cytotoxicity of the final 3D-printed objects.

Taguchi optimization of 3D printed short carbon fiber polyetherketoneketone (CFR PEKK)

In this study, the Taguchi method was utilized to optimize fused filament fabrication (FFF) additive manufacturing with the goal of maximizing the flexural strength of 3D printed polyaryletherketone specimens. We analyzed 3D printed (3DP) carbon fiber reinforced poly-etherketoneketone (CFR PEKK), 3D printed and pressed (3DP + P) CFR PEKK, and injection molded medical grade polyetheretherketone (PEEK) as a control. Fracture surfaces were analyzed via scanning electron microscopy (SEM). The parameters that were varied in the optimization included nozzle diameter, layer height, print speed, raster angle, and nozzle temperature. We analyzed the flexural strength and flexural modulus determined from 3-point bending (ASTM D790). Using Taguchi optimization, the signal to noise ratio (SNR) was calculated to determine the relationship between the input parameters and flexural strength and to determine optimal print settings. Results were confirmed with analysis of variance (ANOVA). The raster angle and layer height were determined to have the greatest impact on the flexural strength of specimens printed in the FFF process for 3DP CFR PEKK. The optimized printing parameters were found to be 0/90 Raster Angle, 0.25 mm layer height, 0.8 mm Nozzle Diameter, 375 °C nozzle temperature, and 1100 mm/min print speed. The optimized 3DP CFR PEKK test samples had a flexural strength of 111.3 ± 5.3 MPa and a flexural modulus of 3.5 GPa. 3DP + P CFR PEKK samples had a flexural strength of 257.2 ± 17.8 MPa and a flexural modulus of 8.2 GPa. Statistical comparisons between means demonstrated that pressing significantly improves both flexural strength and flexural modulus of 3DP CFR PEKK. The results of this study support the hypothesis that post consolidation of 3DP specimens improves mechanical properties. Post-processing composites via pressing may allow greater design freedom within the 3DP process while improving mechanical properties.

3D printing in materials manufacturing industry: A realm of Industry 4.0

Additive manufacturing (AM), also known as 3D printing, is a new manufacturing trend showing promising progress over time in the era of Industry 4.0. So far, various research has been done for increasing the reliability and productivity of a 3D printing process. In this regard, reviewing the existing concepts and forwarding novel research directions are important. This paper reviews and summarizes the process flow, technologies, configurations, and monitoring of AM. It started with the general AM process flow, followed by the definitions and the working principles of various AM technologies and the possible AM configurations, such as traditional and robot-assisted AM. Then, defect detection, fault diagnosis, and open-loop and closed-loop control systems in AM are discussed. It is noted that introducing robots into the assisting mechanism of AM increases the reliability and productivity of the manufacturing process. Moreover, integrating machine learning and conventional control algorithms ensures a closed-loop control in AM, a promising control strategy. Lastly, the paper addresses the challenges and future trends.

A drug-loaded composite coating to improve osteogenic and antibacterial properties of Zn-1Mg porous scaffolds as biodegradable bone implants

Zinc (Zn) alloy porous scaffolds produced by additive manufacturing own customizable structures and biodegradable functions, having a great application potential for repairing bone defect. In this work, a hydroxyapatite (HA)/polydopamine (PDA) composite coating was constructed on the surface of Zn-1Mg porous scaffolds fabricated by laser powder bed fusion, and was loaded with a bioactive factor BMP2 and an antibacterial drug vancomycin. The microstructure, degradation behavior, biocompatibility, antibacterial performance and osteogenic activities were systematically investigated. Compared with as-built Zn-1Mg scaffolds, the rapid increase of Zn²⁺, which resulted to the deteriorated cell viability and osteogenic differentiation, was inhibited due to the physical barrier of the composite coating. In vitro cellular and bacterial assay indicated that the loaded BMP2 and vancomycin considerably enhanced the cytocompatibility and antibacterial performance. Significantly improved osteogenic and antibacterial functions were also observed according to in vivo implantation in the lateral femoral condyle of rats. The design, influence and mechanism of the composite coating were discussed accordingly. It was concluded that the additively manufactured Zn-1Mg porous scaffolds together with the composite coating could modulate biodegradable performance and contribute to effective promotion of bone recovery and antibacterial function.

Morphological analysis of plasma electrolytic oxidation coatings formed on Ti6Al4V alloys manufactured by electron beam powder bed fusion

This study investigates and compares plasma electrolytic oxidation (PEO) coatings produced on wrought Ti6Al4V alloy substrates with those resulting from electron beam powder bed fusion (PBF-EB). For a duration of 1000 s, a phosphate/silicate electrolyte with a current density of 50 A/cm2 was employed to fabricate the coatings. Surface and polished cross-sections of the coated specimens underwent SEM and X-ray diffraction (XRD) analyses. The obtained coatings exhibit differences of up to approximately 18% in thickness and formation, as well as in their anatase phase. The anatase phase is present at a level of 54.09% in the substrates processed by PBF-EB and 38.54% in wrought substrates. After 1000 s of PEO, the coatings formed on the wrought substrates exhibited higher porosity and larger pores (>1 μm) compared to those produced on the PBF-EB specimens. The PBF-EB coatings had lower porosity because they contained fewer pores larger than 1 μm. The findings imply that the unique microstructural arrangement of PBF-EB-produced additively made Ti6Al4V materials plays a significant impact in the development and morphological properties of PEO oxide coatings.

Identifying strategic opportunities through the development of a roadmap for additive manufacturing: The example of Portugal

Additive Manufacturing (AM) demonstrates significant potential with rapid growth and widespread industrial adoption. To support the integration and innovation of AM technologies, the development of guidance tools and support methods are crucial, and a technological roadmap can assist in this effort. Despite its widespread use in production processes, the need for further research on the potential impact of AM remains significant. The full impact of AM is still uncertain and lacks consensus, highlighting the need for increased knowledge and investment from the scientific community and organizations. While the benefits of AM are recognized, the challenges of its adoption are not entirely known. AM will bring changes in the way organizations create, distribute, and derive value. Thus, in this article, a roadmap for AM is proposed and presented as a tool to map technological knowledge on the implementation and evolution of AM and serve as a strategic guide for organizations. The methodology for its elaboration involves three phases: planning and preparation, roadmap development, and review and update. Through a literature review, database and project consultation, and questionnaires to Portuguese companies that use AM in their production process it was possible to characterize the AM technology and through the visual format, based on a time horizon, summarize in a common framework all the information about the current and future state of AM in Portugal. The results of this study show that research and development initiatives are essential to promote the evolution of knowledge of the AM technology. Throughout this study and with the development of the roadmap it is anticipated that in the near future the AM will be widely used for prototyping and manufacturing of components and may be used for direct production in the short to medium term. It was also found that the main obstacles to the implementation of AM are the economic/productivity factors and the shortage of professionals with knowledge and skills in the area.

Comparison of Two Types of Patient Specific Implants (PSI) and Quad Zygoma Implant (QZI) for Rehabilitation of Post-COVID Maxillary Mucormycosis Defect (PCMMD): Finite Element Analysis

Introduction

The residual post-COVID maxillary mucormycosis defect (PCMMD) were extensive, due to unilateral or bilateral maxillectomies. The Goal of rehabilitation of PCMMD is to deliver a prosthetically driven reconstruction. FEA was to evaluate the biomechanical response of PSI struts (PSI 1), PSI Screw retained (PSI 2) and QZI to masticatory load on virtual simulation to improve accuracy and enhance the design.

Aim

To validate and compare the Biomechanical benefit of the PSI struts, PSI Screw retained, QZI in a case of rehabilitation of post-COVID maxillary mucormycosis defect (PCMMD) by FEA study.

Methodology

The result of stress to masticatory load on virtual simulation for (1) Maximum and minimum stress (Von Mises stress); (2) the Displacement (in three positions) and (3) the Deformation (Plastic strain) was compared on virtual simulation for PSI 1 and PSI 2 and QZI.

Conclusion

The FEA and comparative evaluation of PSI 1, PSI 2 and QZI showed a good resistance to displacement. The stress and strain values are low and acceptable. In comparison QZI shows more stress in the anterior region.

3D Printing Technology in Pediatric Orthopedics: a Primer for the Clinician

PURPOSE OF REVIEW

This article reviews the basics of 3D printing and provides an overview of current and future applications of this emerging technology in pediatric orthopedic surgery.

RECENT FINDINGS

Both preoperative and intraoperative utilization of 3D printing technology have enhanced clinical care. Potential benefits include more accurate surgical planning, shortening of a surgical learning curve, decrease in intraoperative blood loss, less operative time, and fluoroscopic time. Furthermore, patient-specific instrumentation can be used to improve the safety and accuracy of surgical care. Patient-physician communication can also benefit from 3D printing technology. 3D printing is rapidly advancing in the field of pediatric orthopedic surgery. It has the potential to increase the value of several pediatric orthopedic procedures by enhancing safety and accuracy while saving time. Future efforts in cost reduction strategies, making patient-specific implants including biologic substitutes and scaffolds, will further increase the relevance of 3D technology in the field of pediatric orthopedic surgery.

Fabrication trueness and internal fit of hybrid abutment crowns fabricated by using additively and subtractively manufactured resins

OBJECTIVES

To evaluate the fabrication trueness and internal fit of hybrid abutment crowns fabricated by using additively and subtractively manufactured restorative materials.

METHODS

A maxillary first premolar crown with a screw access channel was designed onto a digitized master titanium base abutment. This file was used to fabricate 40 crowns additively (Crowntec (CT) and VarseoSmile Crown Plus (VS)) or subtractively (Brilliant Crios (BC) and Vita Enamic (EN)) (n = 10). Crowns were digitized with an intraoral scanner and root mean square method was used to evaluate fabrication trueness. Master abutment and the crowns when seated on the abutment were also digitized with the same intraoral scanner and triple scan method was used to evaluate internal fit. Data were analyzed either with 1-way ANOVA (surface deviations) or Kruskal-Wallis (internal fit) tests (α= 0.05).

RESULTS

CT had the highest overall, external, and marginal surface deviations (P≤.030), whereas BC had the lowest external (P≤.001) and VS and EN had the lowest marginal surface deviations (P≤.007). BC had the highest intaglio surface deviations (P<.001). BC and EN had higher average gap values CT and VS (P≤.006); however, the differences within additively and subtractively manufactured materials were nonsignificant (P≥.858).

CONCLUSIONS

One of the tested additively manufactured resins (CT) resulted in mostly lower trueness than that of other materials. However, deviations at the intaglio and marginal surfaces were generally small and the maximum mean difference among test groups when average gap was considered was 17.4 µm. Therefore, clinical fit of hybrid abutment crowns fabricated with tested materials may be similar.

Numerical investigation of residual stresses in thin-walled additively manufactured structures from selective laser melting

Selective laser melting (SLM), a metal laser powder bed fusion additive manufacturing method, involves several cycles of very high temperature gradient heating and cooling during the solidification of each layer, which can cause the accumulation of detrimental residual stresses in the 3D printed structure. This work uses a thermo-mechanical computational modeling approach to investigate the formation of residual stresses in thin-walled structures and also investigates the effects of varying taper on the evolution of residual stress profiles of the build. Three material grades; namely, Titanium alloy (Ti64), Stainless steel (SS316L) and Inconel (IN718) have been used for this study. The results show that varying taper thickness up to a certain value has a considerable effect on residual stress evolutions in thin-wall structures, however, beyond a certain value of the taper level, the residual stresses are observed to converge. Also, it is observed that the tensile stresses at the edges of the wall are almost equal or exceed the yield stress of the materials. Among the three material grades considered, the magnitude of residual stress was higher in Ti64 and the stresses are dominant in the build direction. The simulation framework is also applied to analyze the effect of residual stresses on the mechanical properties of complex thin-wall structures such as TPMS (Triply Periodic Minimum Surfaces) lattice structure, using Schwarz Primitive (SP) as a case study. It is observed that the residual stresses lower the effective elastic properties of the lattice structures by 6% ∼ 10% for the three material grades but has no effect on the effective plastic behavior of the material.

Mechanically promoted lipid-based filaments via composition tuning for extrusion-based 3D-printing

Lipid excipients are favorable materials in pharmaceutical formulations owing to their natural, biodegradable, low-toxic and solubility/permeability enhancing properties. The application of these materials with advanced manufacturing platforms, particularly filament-based 3D-printing, is attractive for personalized manufacturing of thermolabile drugs. However, the filament's weak mechanical properties limit their full potential. In this study, highly flexible filaments were extruded using PG6-C16P, a lipid-based excipient belonging to the group of polyglycerol esters of fatty acids (PGFAs), based on tuning the ratio between its major and minor composition fractions. Increasing the percentage of the minor fractions in the system was found to enhance the relevant mechanical filament properties by 50-fold, guaranteeing a flawless 3D-printability. Applying a novel liquid feeding approach further improved the mechanical filament properties at lower percentage of minor fractions, whilst circumventing the issues associated with the standard extrusion approach such as low throughput. Upon drug incorporation, the filaments retained high mechanical properties with a controlled drug release pattern. This work demonstrates PG6-C16 P as an advanced lipid-based material and a competitive printing excipient that can empower filament-based 3D-printing.