Three‐dimensional printing: The potential technology widely used in medical fields

Recent advances in additive manufacturing of patient-specific devices for dental and maxillofacial rehabilitation

OBJECTIVES

Customization and the production of patient-specific devices, tailoring the unique anatomy of each patient's jaw and facial structures, are the new frontiers in dentistry and maxillofacial surgery. As a technological advancement, additive manufacturing has been applied to produce customized objects based on 3D computerized models. Therefore, this paper presents advances in additive manufacturing strategies for patient-specific devices in diverse dental specialties.

METHODS

This paper overviews current 3D printing techniques to fabricate dental and maxillofacial devices. Then, the most recent literature (2018-2023) available in scientific databases reporting advances in 3D-printed patient-specific devices for dental and maxillofacial applications is critically discussed, focusing on the major outcomes, material-related details, and potential clinical advantages.

RESULTS

The recent application of 3D-printed customized devices in oral prosthodontics, implantology and maxillofacial surgery, periodontics, orthodontics, and endodontics are presented. Moreover, the potential application of 4D printing as an advanced manufacturing technology and the challenges and future perspectives for additive manufacturing in the dental and maxillofacial area are reported.

SIGNIFICANCE

Additive manufacturing techniques have been designed to benefit several areas of dentistry, and the technologies, materials, and devices continue to be optimized. Image-based and accurately printed patient-specific devices to replace, repair, and regenerate dental and maxillofacial structures hold significant potential to maximize the standard of care in dentistry.

Metal and Polymer Based Composites Manufactured Using Additive Manufacturing-A Brief Review

This review examines the mechanical performance of metal- and polymer-based composites fabricated using additive manufacturing (AM) techniques. Composite materials have significantly influenced various industries due to their exceptional reliability and effectiveness. As technology advances, new types of composite reinforcements, such as novel chemical-based and bio-based, and new fabrication techniques are utilized to develop high-performance composite materials. AM, a widely popular concept poised to shape the development of Industry 4.0, is also being utilized in the production of composite materials. Comparing AM-based manufacturing processes to traditional methods reveals significant variations in the performance of the resulting composites. The primary objective of this review is to offer a comprehensive understanding of metal- and polymer-based composites and their applications in diverse fields. Further on this review delves into the intricate details of metal- and polymer-based composites, shedding light on their mechanical performance and exploring the various industries and sectors where they find utility.

Highly Porous Gas-Blown Hydrogels for Direct Cell Encapsulation with High Cell Viability

Cell transplant therapies show potential as treatments for a large number of diseases. The encapsulation of cells within hydrogels is often used to mimic the extracellular matrix and protect cells from the body's immune response. However, cell encapsulation can be limited in terms of both scaffold size and cell viability due to poor nutrient and waste transport throughout the bulk of larger volume hydrogels. Strategies to address this issue include creating prevascularized or porous structured materials. For example, cell-laden hydrogels can be formed by porogen leaching or three-dimensional printing, but these techniques involve the use of multiple materials, long preparation times, and/or specialized equipment. Postfabrication cell seeding in porous scaffolds can result in inconsistent cell density throughout scaffold volumes and typically requires a bioreactor to ensure even cell distribution. In this study, we developed a highly cytocompatible direct cell encapsulation method during the rapid fabrication of porous hydrogels. Using sodium bicarbonate and citric acid as blowing agents, we employed photocurable polymers to produce highly porous materials within a matter of minutes. Cells were directly encapsulated within methacrylated poly(vinyl alcohol), poly(ethylene glycol), and gelatin hydrogels at viabilities as high as 93% by controlling solution variables, such as citric acid content, viscosity, pH, and curing time. Cell viability within the resulting porous constructs was high (>80%) over 14 days of analysis with multiple cell types. This work provides a simple, versatile, and tunable method for cell encapsulation within highly porous constructs that can be built upon in future work for the delivery of cell-based therapies. Impact Statement This simple method to obtain cell-laden hydrogel foams allows direct cell encapsulation within biomaterials without the need for porogens or microcarriers, while maintaining high cell viability. The successful encapsulation of multiple cell types into gas-blown hydrogels with varied chemistries shows the versatility of this method. While this work focuses on photocrosslinkable polymers, any quick gelling material could be used for foam fabrication in expansion of this work. The potential future impact of this work on the treatment of diseases and injuries that utilize cell therapies is wide-ranging.

Chemistry in light-induced 3D printing

In the last few years, 3D printing has evolved from its original niche applications, such as rapid prototyping and hobbyists, towards many applications in industry, research and everyday life. This involved an evolution in terms of equipment, software and, most of all, in materials. Among the different available 3D printing technologies, the light activated ones need particular attention from a chemical point of view, since those are based on photocurable formulations and in situ rapid solidification via photopolymerization. In this article, the chemical aspects beyond the preparation of a formulation for light-induced 3D printing are analyzed and explained, aiming at giving more tools for the development of new photocurable materials that can be used for the fabrication of innovative 3D printable devices.

Graphical abstract

A randomized controlled trial: evaluation of efficiency and safety of a novel surgical guide in the extraction of deeply impacted supernumerary teeth in the anterior maxilla

Background

Preoperative X-ray and cone-beam computed tomography (CBCT) are helpful for locating supernumerary teeth, but the images cannot be transferred to the operation. To design a novel surgical guide plate for intraoperative navigation, we transfer the patient's oral CBCT and gypsum model scan data to a computer for analysis. In our study, we evaluate the efficiency and safety of a novel surgical guide plate for the extraction of deeply impacted supernumerary teeth (DIMSNT) in the anterior maxilla.

Methods

Forty patients treated at the Department of School & Hospital of Stomatology, Wenzhou Medical University from March 2019 to December 2020 with DIMSNT (type II/III according to Liu et al.) in the anterior maxilla were randomly divided into 2 groups (20 patients for each group) for the extraction. For group I, a novel surgical guide was selected using CBCT and gypsum model scan. In contrast, for group II who underwent freehand surgery, only the CBCT data was used. The evaluation of operation time, complications, satisfaction score, and the number of cases that underwent extraction immediately after removing the bone were performed to assess the efficiency and safety of this novel surgical plate.

Results

All patients completed the surgery successfully. The guides for group I had a good application effect. Group I's operation time (23.35±5.39 min) was shorter than group II (29.60±9.76 min) (P=0.0194). The average pain degree of group I (1.8±1.08) was significantly less than group II (2.82±1.68) (P<0.05). The average swelling score of group I (34) was significantly less than group II (44.7). Patient satisfaction was significantly higher in group I (8.95±1.05) than in group II (7.90±1.51) (P=0.0152).

Conclusions

The novel surgical guide assisted with DIMSNT extraction have been effective in improving the quality of the surgery, patient satisfaction, and reduce its difficulty and duration. We can construct a surgical guide plate to guide the incision and osteotomy in DIMSNT surgery through the data analysis of DIMSNT on computer, which has a broad application prospect for clinical use.

Trial registration

Chinese Clinical Trial Registry ChiCTR2100054523.

Preparation of Artificial Pavement Coarse Aggregate Using 3D Printing Technology

Coarse aggregate is the main component of asphalt mixtures, and differences in its morphology directly impact road performance. The utilization of standard aggregates can benefit the standard design and performance improvement. In this study, 3D printing technology was adopted to prepare artificial aggregates with specific shapes for the purpose of making the properties of artificial aggregates to be similar to the properties of natural aggregates. Through a series of material experiments, the optimal cement-based material ratio for the preparation of high-strength artificial aggregates and corresponding manufacturing procedures have been determined. The performance of the artificial aggregates has been verified by comparing the physical and mechanical properties with those of natural aggregates. Results indicate that using 3D printing technology to generate the standard coarse aggregate is feasible, but its high cost in implementation cannot be ignored. The 3D shape of the artificial aggregate prepared by the grouting molding process has a good consistency with the natural aggregate, and the relative deviation of the overall macro-scale volume index of the artificial aggregate is within 4%. The average Los Angeles abrasion loss of artificial cement-based aggregate is 15.2%, which is higher than that of diabase aggregate, but significantly lower than that of granite aggregate and limestone aggregate. In a nutshell, 3D printed aggregates prepared using the optimized cement-based material ratio and corresponding manufacturing procedures have superior physical and mechanical performance, which provides technical support for the test standardization and engineering application of asphalt pavements.

Early preclinical evaluation of a novel, computer aided designed, 3D printed, bioresorbable posterior cricoid scaffold

OBJECTIVES

The posterior cricoid split with rib graft is a procedure that elegantly corrects pediatric posterior glottic stenosis and subglottic stenosis. Currently, the procedure requires harvesting of rib cartilage which leaves room for optimization. With use of three dimensional printing technology, our objective was to design a device that would negate the need for costal cartilage harvesting in this procedure.

METHODS

An optimized, novel polycaprolactone scaffold was designed using computer aided design software and three dimensional printing. A pilot proof of concept study was conducted with implantation of the device in three porcine animal subjects. Device was evaluated by post-procedural clinical course, endoscopic exams, post-mortem exam, and histological evaluation.

RESULTS

A series of variably sized scaffolds were created. The scaffolds showed structural integrity and successfully expanded the cricoid cartilage in the porcine model study. Post-operative endoscopy and clinical exams demonstrated no signs of implant instability or failure. Gross and histologic exams showed successful mucosalization over the scaffold and cartilage ingrowth by six weeks.

CONCLUSION

This porcine animal pilot study demonstrated early success of a computer-aided designed, 3D printed, bioresorbable PCL posterior graft scaffold. The scaffolds eliminate the need for costal cartilage harvesting and had excellent surgical usability. The scaffolds functioned as designed, offering proof of concept and grounds for further evaluation to expand on this small pilot study with larger animal studies and continued design refinement.

Applications of additive manufacturing (AM) in sustainable energy generation and battle against COVID-19 pandemic: The knowledge evolution of 3D printing

Sustainable and cleaner manufacturing systems have found broad applications in industrial processes, especially aerospace, automotive and power generation. Conventional manufacturing methods are highly unsustainable regarding carbon emissions, energy consumption, material wastage, costly shipment and complex supply management. Besides, during global COVID-19 pandemic, advanced fabrication and management strategies were extremely required to fulfill the shortfall of basic and medical emergency supplies. Three-dimensional printing (3DP) reduces global energy consumption and CO₂ emissions related to industrial manufacturing. Various renewable energy harvesting mechanisms utilizing solar, wind, tidal and human potential have been fabricated through additive manufacturing. 3D printing aided the manufacturing companies in combating the deficiencies of medical healthcare devices for patients and professionals globally. In this regard, 3D printed medical face shields, respiratory masks, personal protective equipment, PLA-based recyclable air filtration masks, additively manufactured ideal tissue models and new information technology (IT) based rapid manufacturing are some significant contributions of 3DP. Furthermore, a bibliometric study of 3D printing research was conducted in CiteSpace. The most influential keywords and latest research frontiers were found and the 3DP knowledge was categorized into 10 diverse research themes. The potential challenges incurred by AM industry during the pandemic were categorized in terms of design, safety, manufacturing, certification and legal issues. Significantly, this study highlights the versatile role of 3DP in battle against COVID-19 pandemic and provides up-to-date research frontiers, leading the readers to focus on the current hurdles encountered by AM industry, henceforth conduct further investigations to enhance 3DP technology.

Fabrication of Biomedical Scaffolds Using Biodegradable Polymers

Degradable polymers are used widely in tissue engineering and regenerative medicine. Maturing capabilities in additive manufacturing coupled with advances in orthogonal chemical functionalization methodologies have enabled a rapid evolution of defect-specific form factors and strategies for designing and creating bioactive scaffolds. However, these defect-specific scaffolds, especially when utilizing degradable polymers as the base material, present processing challenges that are distinct and unique from other classes of materials. The goal of this review is to provide a guide for the fabrication of biodegradable polymer-based scaffolds that includes the complete pathway starting from selecting materials, choosing the correct fabrication method, and considering the requirements for tissue specific applications of the scaffold.

Improvement of Interlayer Adhesion and Heat Resistance of Biodegradable Ternary Blend Composite 3D Printing

Poly(lactic acid) (PLA) filaments have been the most used in fused deposition modeling (FDM) 3D printing. The filaments, based on PLA, are continuing to be developed to overcome brittleness, low heat resistance, and obtain superior mechanical performance in 3D printing. From our previous study, the binary blend composites from PLA and poly(butylene adipate-co-terephthalate) (PBAT) with nano talc (PLA/PBAT/nano talc) at 70/30/10 showed an improvement in toughness and printability in FDM 3D printing. Nevertheless, interlayer adhesion, anisotropic characteristics, and heat resistance have been promoted for further application in FDM 3D printing. In this study, binary and ternary blend composites from PLA/PBAT and poly(butylene succinate) (PBS) with nano talc were prepared at a ratio of PLA 70 wt. % and blending with PBAT or PBS at 30 wt. % and nano talc at 10 wt. %. The materials were compounded via a twin-screw extruder and applied to the filament using a capillary rheometer. PLA/PBAT/PBS/nano talc blend composites were printed using FDM 3D printing. Thermal analysis, viscosity, interlayer adhesion, mechanical properties, and dimensional accuracy of binary and ternary blend composite 3D prints were investigated. The incorporation of of PBS-enhanced crystallinity of the blend composite 3D prints resulted in an improvement to mechanical properties, heat resistance, and anisotropic characteristics. Flexibility of the blend composites was obtained by presentation of PBAT. It should be noted that the core-shell morphology of the ternary blend influenced the reduction of volume shrinkage, which obtained good surface roughness and dimensional accuracy in the ternary blend composite 3D printing.

Biological and mechanical evaluation of mineralized-hydrogel scaffolds for tissue engineering applications

Chitosan and gelatin have been extensively used in tissue engineering for a wide range of different applications, such as wound healing or bone regeneration, due to their advantages: excellent biocompatibility (promoting cell adhesion and proliferation), low price and biodegradability. Nonetheless, their main drawback is that they have poor mechanical properties, consequently restricting their use in bone tissue engineering. In previous studies, both materials were cross-linked, with added calcium minerals, which led to an improvement in both mechanical and biological properties. Therefore, this study carries out a mechanical and biological characterization of mineral-hydrogel scaffolds in order to find the best compositions. Different proportions of calcium compounds (CaCO₃ and CaHPO₄) are used to make up between 20% and 30% of the minerals used in a mineral-hydrogel mix. This addition of minerals enhances not only the mechanical properties, but also the biological ones. On the one hand, the higher the amount of minerals added to the composition, the better the mechanical properties obtained. Additionally, as the proportion of CaCO₃ in comparison with CaHPO₄ rises, the mechanical properties improve. On the other hand, both cell proliferation and mineralization are improved with the addition of calcium minerals.

3D printing promotes the development of drugs

3D printing is an emerging field that can be found in medicine, electronics, aviation and other fields. 3D printing, with its personalized and highly customized characteristics, has great potential in the pharmaceutical industry. We were interested in how 3D printing can be used in drug fields. To find out 3D printing's application in drug fields, we collected the literature by combining the keywords "3D printing"/"additive manufacturing" and "drug"/"tablet". We found that 3D printing technology has the following applications in medicine: firstly, it can print pills on demand according to the individual condition of the patient, making the dosage more suitable for each patient's own physical condition; secondly, it can print tablets with specific shape and structure to control the release rate; thirdly, it can precisely control the distribution of cells, extracellular matrix and biomaterials to build organs or organ-on-a-chip for drug testing; finally, it could print loose porous pills to reduce swallowing difficulties, or be used to make transdermal microneedle patches to reduce pain of patients.

Evaluating FDM Process Parameter Sensitive Mechanical Performance of Elastomers at Various Strain Rates of Loading

To optimize the mechanical performance of fused deposition modelling (FDM) fabricated parts, it is necessary to evaluate the influence of process parameters on the resulting mechanical performance. The main focus of the study was to characterize the influence of the initial process parameters on the mechanical performance of thermoplastic polyurethane under a quasi-static and high strain rate (~2500 s⁻¹). The effects of infill percentage, layer height, and raster orientation on the mechanical properties of an FDM-fabricated part were evaluated. At a quasi-static rate of loading, layer height was found to be the most significant factor (36.5% enhancement in tensile strength). As the layer height of the sample increased from 0.1 to 0.4 mm, the resulting tensile strength sample was decreased by 36.5%. At a high-strain rate of loading, infill percentage was found to be the most critical factor influencing the mechanical strength of the sample (12.4% enhancement of compressive strength at 100% as compared to 80% infill). Furthermore, statistical analysis revealed the presence of significant interactions between the input parameters. Finally, using an artificial neural networking approach, we evaluated a regression model that related the process parameters (input factors) to the resulting strength of the samples.

Bone metabolism regulation: Implications for the treatment of bone diseases

Bone cells in the human body are continuously engaged in cellular metabolism, including the interaction between bone cells, the interaction between the erythropoietic cells of the bone marrow and stromal cells, for the remodeling and reconstruction of bone. Osteoclasts and osteoblasts play an important role in bone metabolism. Diseases occur when bone metabolism is abnormal, but little is known about the signaling pathways that affect bone metabolism. The study of these signaling pathways will help us to use the relevant techniques to intervene, so as to improve the condition. The study of these signaling pathways will help us to use the relevant techniques to intervene, so as to improve the condition. I believe they will shine in the diagnosis and treatment of future clinical bone diseases.