Additive Manufacturing Post-Processing Treatments, a Review with Emphasis on Mechanical Characteristics

Comprehensive review of polyetheretherketone use in dentistry

PURPOSE

This study aimed to comprehensively summarize the current state, shortcomings, and challenges regarding the use of polyetheretherketone (PEEK) in various fields of stomatology.

STUDY SELECTION

This study reviewed articles retrieved from PubMed, Google Scholar, Web of Science, and ScienceDirect databases. The main keywords used during the search included "polyetheretherketone (PEEK)," "dental materials," "orthodontics," "prosthodontics," "oral implantology," "oral and maxillofacial surgery," "periodontics" "osseointegration," and "surface modification."

RESULTS

Numerous studies have highlighted the properties of PEEK that contribute to its usefulness in dentistry, including its high biocompatibility, fracture resistance, aesthetics, radiolucency, and bone-like mechanical properties. Promising applications of PEEK in dentistry include orthodontic archwires, interceptive orthodontic appliances, fixed lingual retainers, crowns, post and cores, fixed partial dentures, removable partial dentures, maxillofacial prostheses, dental implants, implant abutments, alveolar bone scaffolds, jaw reconstruction, temporomandibular joint reconstruction, periodontal splints, and occlusal splints. In addition, many in vitro and in vivo experiments have demonstrated that the in vivo bone integration capability can be effectively improved using advanced surface modification technologies.

CONCLUSIONS

PEEK has been explored in several dentistry fields owing to its excellent properties. PEEK and its modifications are most frequently used in clinical dentistry. However, most of its applications are based on in vitro or short-term in vivo evaluations. Additional long-term clinical data are required to demonstrate the applicability and superiority of PEEK in dentistry.

Can the Dimensional Optimisation of 3D FDM-Manufactured Parts Be a Solution for a Correct Design?

Additive manufacturing technology, also known as 3D printing, has emerged as a viable alternative in modern manufacturing processes. Unlike traditional manufacturing methods, which often involve complex mechanical operations that can lead to errors and inconsistencies in the final product, additive technology offers a new approach that enables precise layer-by-layer production with improved geometric accuracy, reduced material consumption and increased design flexibility. Geometrical accuracy is a critical issue in industries such as aerospace, automotive, medicine and consumer goods, hence the importance of the following question: can the dimensional optimisation of 3D FDM-manufactured parts be a solution for correct design? This paper presents a complex study of model parts printed from four common polymers used in fused deposition modelling (FDM) additive technology, namely ABS (acrylonitrile-butadiene-styrene), PLA (polylactic acid), HIPS (high-impact polystyrene) and PETG (polyethylene terephthalate glycol). The results of the methodology used highlight the dimensional changes that need to be made at the design stage, depending on the direction of printing and the type of geometric elements in the final part.

Finite element analysis and in vitro tests on endurance life and durability of composite bone substitutes

Bone structures facilitate the regeneration and repair of bone tissue in regions where it has been damaged or destroyed, either temporarily or permanently. Therefore, the bone's fatigue strength and durability are crucial to its efficacy and longevity. Several variables, such as the construct's material qualities, design, and production procedure, loading and unloading cycles, and physiological conditions influence the endurance life of bone constructs. Metals, ceramics, and polymers are all routinely utilized to create bone substitutes, and each of these materials has unique features that might affect the fatigue strength and endurance life of the final product. The mechanical performance and capacity to promote bone tissue regeneration may be affected by the scaffold's design, porosity, and pore size. Researchers employ mechanical testing under cyclic loading circumstances as one example of an experimental approach used to assess bone construction endurance. These analyses can give us important information about the stress-strain behavior, resistance to multiple loading cycles, and fatigue strength of the new structure. Predicting the endurance life of the developed construct may also be possible with the use of simulations and numerical analyses. Hence, in order to create reliable and efficient constructs for bone tissue engineering, it is crucial to understand their fatigue strength and durability. The purpose of this study is to analyze the effective parameters for fatigue strength of bone structures and to gather the models and evaluations utilized in endurance life assessments.

Enhanced Piezoelectric Performance of PVDF-TrFE Nanofibers through Annealing for Tissue Engineering Applications

This study investigates bioelectric stimulation's role in tissue regeneration by enhancing the piezoelectric properties of tissue-engineered grafts using annealed poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) scaffolds. Annealing at temperatures of 80°C, 100°C, 120°C, and 140°C was assessed for its impact on material properties and physiological utility. Analytical techniques such as Differential Scanning Calorimetry (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) revealed increased crystallinity with higher annealing temperatures, peaking in β-phase content and crystallinity at 140°C. Scanning Electron Microscopy (SEM) showed that 140°C annealed scaffolds had enhanced lamellar structures, increased porosity, and maximum piezoelectric response. Mechanical tests indicated that 140°C annealing improved elastic modulus, tensile strength, and substrate stiffness, aligning these properties with physiological soft tissues. In vitro assessments in Schwann cells demonstrated favorable responses, with increased cell proliferation, contraction, and extracellular matrix attachment. Additionally, genes linked to extracellular matrix production, vascularization, and calcium signaling were upregulated. The foreign body response in C57BL/6 mice, evaluated through Hematoxylin and Eosin (H&E) and Picrosirius Red staining, showed no differences between scaffold groups, supporting the potential for future functional evaluation of the annealed group in tissue repair.

Advancements in Custom 3D-Printed Titanium Interbody Spinal Fusion Cages and Their Relevance in Personalized Spine Care

3D-printing technology has revolutionized spinal implant manufacturing, particularly in developing personalized and custom-fit titanium interbody fusion cages. These cages are pivotal in supporting inter-vertebral stability, promoting bone growth, and restoring spinal alignment. This article reviews the latest advancements in 3D-printed titanium interbody fusion cages, emphasizing their relevance in modern personalized surgical spine care protocols applied to common clinical scenarios. Furthermore, the authors review the various printing and post-printing processing technologies and discuss how engineering and design are deployed to tailor each type of implant to its patient-specific clinical application, highlighting how anatomical and biomechanical considerations impact their development and manufacturing processes to achieve optimum osteoinductive and osteoconductive properties. The article further examines the benefits of 3D printing, such as customizable geometry and porosity, that enhance osteointegration and mechanical compatibility, offering a leap forward in patient-specific solutions. The comparative analysis provided by the authors underscores the unique challenges and solutions in designing cervical, and lumbar spine implants, including load-bearing requirements and bioactivity with surrounding bony tissue to promote cell attachment. Additionally, the authors discuss the clinical outcomes associated with these implants, including the implications of improvements in surgical precision on patient outcomes. Lastly, they address strategies to overcome implementation challenges in healthcare facilities, which often resist new technology acquisitions due to perceived cost overruns and preconceived notions that hinder potential savings by providing customized surgical implants with the potential for lower complication and revision rates. This comprehensive review aims to provide insights into how modern 3D-printed titanium interbody fusion cages are made, explain quality standards, and how they may impact personalized surgical spine care.

Vat Photopolymerization 3D Printing in Dentistry: A Comprehensive Review of Actual Popular Technologies

In this comprehensive review, the current state of the art and recent advances in 3D printing in dentistry are explored. This article provides an overview of the fundamental principles of 3D printing with a focus on vat photopolymerization (VP), the most commonly used technological principle in dental practice, which includes SLA, DLP, and LCD (or mSLA) technologies. The advantages, disadvantages, and shortcomings of these technologies are also discussed. This article delves into the key stages of the dental 3D printing process, from computer-aided design (CAD) to postprocessing, emphasizing the importance of postrinsing and postcuring to ensure the biocompatibility of custom-made medical devices. Legal considerations and regulatory obligations related to the production of custom medical devices through 3D printing are also addressed. This article serves as a valuable resource for dental practitioners, researchers, and health care professionals interested in applying this innovative technology in clinical practice.

Tailoring Multiple Strengthening Phases to Achieve Superior High-Temperature Strength in Cast Mg-RE-Ag Alloys

Mg alloys with excellent high-temperature mechanical properties are urgently desired to meet the design requirements of new-generation aircraft. Herein, novel cast Mg-10Gd-2Y-0.4Zn-0.2Ca-0.5Zr-xAg alloys were designed and prepared according to the advantages of multi-component alloying. The SEM and XRD results revealed that the as-cast microstructures contained α-Mg grains, β, and Zr-containing phase. As Ag rose from 0 wt.% to 2.0 wt.%, the grain size was refined from 40.7 μm to 33.5 μm, and the β phase significantly increased. The TEM observations revealed that the nano-scaled γ' phase could be induced to precipitate in the α-Mg matrix by the addition of Ag. The stacking sequence of lamellar γ' phases is ABCA. The multiple strengthening phases, including β phase, γ' phases, and Zr-containing particles, were effectively tailored through alloying and synergistically enhanced the mechanical properties. The ultimate tensile strength increased from 154.0 ± 3.5 MPa to 231.0 ± 4.0 MPa at 548 K when Ag was added from 0 to 2.0 wt.%. Compared to the Ag-free alloy, the as-cast alloy containing 2.0 wt.% Ag exhibited a minor reduction in ultimate tensile strength (7.0 ± 4.0 MPa) from 498 K to 548 K. The excellent high-temperature performance of the newly developed Mg-RE-Ag alloy has great value in promoting the use of Mg alloys in aviation industries.

The Tensile, Thermal and Flame-Retardant Properties of Polyetherimide and Polyetherketoneketone Processed via Fused Filament Fabrication

Polymer materials are increasingly widely used in high-fire-risk applications, such as aviation interior components. This study aimed to compare the tensile, thermal, and flame-retardant properties of test samples made from ultra-performance materials, polyetherimide (PEI) and polyetherketoneketone (PEKK), using the fused filament fabrication process (FFF). The tensile tests were performed for these materials at different raster angles (0, 45, and 90°). The thermomechanical tests were done in the axial, perpendicular, and through-thickness directions to the extruded filaments. The impact of printing parameters on the flame retardancy of 3D-printed samples was investigated in vertical burn tests with varying specimen thicknesses and printing directions. Experimentally, it was testified that PEKK had better isotropic behaviour than PEI for mechanical performance, thermal expansion, and fire-resistant properties, which are essential in fabricating intricately shaped products.

Application of Artificial Intelligence for Surface Roughness Prediction of Additively Manufactured Components

Additive manufacturing has gained significant popularity from a manufacturing perspective due to its potential for improving production efficiency. However, ensuring consistent product quality within predetermined equipment, cost, and time constraints remains a persistent challenge. Surface roughness, a crucial quality parameter, presents difficulties in meeting the required standards, posing significant challenges in industries such as automotive, aerospace, medical devices, energy, optics, and electronics manufacturing, where surface quality directly impacts performance and functionality. As a result, researchers have given great attention to improving the quality of manufactured parts, particularly by predicting surface roughness using different parameters related to the manufactured parts. Artificial intelligence (AI) is one of the methods used by researchers to predict the surface quality of additively fabricated parts. Numerous research studies have developed models utilizing AI methods, including recent deep learning and machine learning approaches, which are effective in cost reduction and saving time, and are emerging as a promising technique. This paper presents the recent advancements in machine learning and AI deep learning techniques employed by researchers. Additionally, the paper discusses the limitations, challenges, and future directions for applying AI in surface roughness prediction for additively manufactured components. Through this review paper, it becomes evident that integrating AI methodologies holds great potential to improve the productivity and competitiveness of the additive manufacturing process. This integration minimizes the need for re-processing machined components and ensures compliance with technical specifications. By leveraging AI, the industry can enhance efficiency and overcome the challenges associated with achieving consistent product quality in additive manufacturing.

The Mechanical, Thermal, and Biological Properties of Materials Intended for Dental Implants: A Comparison of Three Types of Poly(aryl-ether-ketones) (PEEK and PEKK)

Regarding the dynamic development of 3D printing technology, as well as its application in a growing part of industries, i.e., in the automotive industry, construction industry, medical industry, etc., there is a notable opportunity for its application in producing dental implants, which presents a promising alternative to traditional implant manufacturing methods. The medical industry is very restrictive regarding the applied materials, and it is necessary to use materials that exhibit very good mechanical and thermal parameters, show clinical indifference and biocompatibility, are non-allergenic and non-cancerous, and are likely to sterilize. Such materials are poly(aryl-ether-ketone)s (PAEK)s, mainly poly(ether-ether-ketone) (PEEK) and poly(ether-ketone-ketone) (PEKK), that are found to be high-performance polymers and can be defined as materials that retain their functionality even in extreme conditions. In the present paper, two types of PEEKs and PEKK were compared regarding their structural, mechanical, and thermal properties along with the biological activity toward selected strains. The tested samples were obtained with Fused Deposition Modeling (FDM) technology. The PEKK, after heat treatment, exhibits the most promising mechanical properties as well as less bacterial adhesion on its surface when compared to both PEEKs. Consequently, among the evaluated materials, PEKK after heat treatment stands out as the optimal selection for a dental prosthesis.

Optimization of 3D Printing Parameters for Enhanced Surface Quality and Wear Resistance

In recent years, there has been a growing interest in the field of 3D printing technology. Among the various technologies available, fused deposition modeling (FDM) has emerged as the most popular and widely used method. However, achieving optimal results with FDM presents a significant challenge due to the selection of appropriate process parameters. Therefore, the objective of this research was to investigate the impact of process parameters on the tribological and frictional behavior of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) 3D-printed parts. The design of experiments (DOE) technique was used considering the input design parameters (infill percentage and layer thickness) as variables. The friction coefficient values and the wear were determined by experimental testing of the polymers on a universal tribometer employing plane friction coupling. Multi-response optimization methodology and analysis of variance (ANOVA) were used to highlight the dependency between the coefficient of friction, surface roughness parameters, and wear on the process parameters. The optimization analysis revealed that the optimal 3D printing input parameters for achieving the minimum coefficient of friction and linear wear were found to be an infill percentage of 50% and layer thickness of 0.1 mm (for ABS material), and an infill percentage of 50%, layer thickness of 0.15 mm (for PLA material). The suggested optimization methodology (which involves minimizing the coefficient of friction and cumulative linear wear) through the optimized parameter obtained provides the opportunity to select the most favorable design conditions contributing to a more sustainable approach to manufacturing by reducing overall material consumption.