Structural and Biomedical Properties of Common Additively Manufactured Biomaterials: A Concise Review

Ultrastructural and immunohistochemical evaluation of hyperplastic soft tissues surrounding dental implants in fibular jaws

In reconstructive surgery, complications post-fibula free flap (FFF) reconstruction, notably peri-implant hyperplasia, are significant yet understudied. This study analyzed peri-implant hyperplastic tissue surrounding FFF, alongside peri-implantitis and foreign body granulation (FBG) tissues from patients treated at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Using light microscopy, pseudoepitheliomatous hyperplasia, anucleate and pyknotic prickle cells, and excessive collagen deposition were observed in FFF hyperplastic tissue. Ultrastructural analyses revealed abnormal structures, including hemidesmosome dilation, bacterial invasion, and endoplasmic reticulum (ER) swelling. In immunohistochemical analysis, unfolded protein-response markers ATF6, PERK, XBP1, inflammatory marker NFκB, necroptosis marker MLKL, apoptosis marker GADD153, autophagy marker LC3, epithelial-mesenchymal transition, and angiogenesis markers were expressed variably in hyperplastic tissue surrounding FFF implants, peri-implantitis, and FBG tissues. NFκB expression was higher in peri-implantitis and FBG tissues compared to hyperplastic tissue surrounding FFF implants. PERK expression exceeded XBP1 significantly in FFF hyperplastic tissue, while expression levels of PERK, XBP1, and ATF6 were not significantly different in peri-implantitis and FBG tissues. These findings provide valuable insights into the interconnected roles of ER stress, necroptosis, apoptosis, and angiogenesis in the pathogenesis of oral pathologies, offering a foundation for innovative strategies in dental implant rehabilitation management and prevention.

Application of Artificial Intelligence at All Stages of Bone Tissue Engineering

The development of artificial intelligence (AI) has revolutionized medical care in recent years and plays a vital role in a number of areas, such as diagnostics and forecasting. In this review, we discuss the most promising areas of AI application to the field of bone tissue engineering and prosthetics, which can drastically benefit from AI-assisted optimization and patient personalization of implants and scaffolds in ways ranging from visualization and real-time monitoring to the implantation cases prediction, thereby leveraging the compromise between specific architecture decisions, material choice, and synthesis procedure. With the emphasized crucial role of accuracy and robustness of developed AI algorithms, especially in bone tissue engineering, it was shown that rigorous validation and testing, demanding large datasets and extensive clinical trials, are essential, and we discuss how through developing multidisciplinary cooperation among biology, chemistry with materials science, and AI, these challenges can be addressed.

Design and fabrication of biomimicking radially graded scaffolds via digital light processing 3D printing for bone regeneration

Scaffolds are an essential component in bone tissue engineering (BTE). However, most of the current BTE scaffolds are homogeneous structures and do not resemble the graded architectures of native bone. In the current study, four types of biomimicking scaffold designs based on gyroid (G) and primitive (P) units with radially graded pore sizes were devised, and scaffolds of these designs with two porosity groups (65 vol% and 75 vol%) were fabricated via digital light processing (DLP) 3D printing using biphasic calcium phosphate (BCP). Scaffolds of the gyroid-gyroid (G-G) design displayed better dimensional accuracy, compressive property, and cell proliferation rate than gyroid-primitive (G-P), primitive-gyroid (P-G), and primitive-primitive (P-P) scaffolds. Subsequently, graded G-G scaffolds with different porosities were fabricated and the relationship between compressive strength and porosity was determined. Furthermore, the sintered BCP bioceramics fabricated via current manufacturing process exhibited excellent biocompatibility and bioactivity, indicating their high potential for BTE.

Functionalization of 3D-Printed Titanium Scaffolds with Elastin-like Recombinamers to Improve Cell Colonization and Osteoinduction

The 3D printing of titanium (Ti) offers countless possibilities for the development of personalized implants with suitable mechanical properties for different medical applications. However, the poor bioactivity of Ti is still a challenge that needs to be addressed to promote scaffold osseointegration. The aim of the present study was to functionalize Ti scaffolds with genetically modified elastin-like recombinamers (ELRs), synthetic polymeric proteins containing the elastin epitopes responsible for their mechanical properties and for promoting mesenchymal stem cell (MSC) recruitment, proliferation, and differentiation to ultimately increase scaffold osseointegration. To this end, ELRs containing specific cell-adhesive (RGD) and/or osteoinductive (SNA15) moieties were covalently attached to Ti scaffolds. Cell adhesion, proliferation, and colonization were enhanced on those scaffolds functionalized with RGD-ELR, while differentiation was promoted on those with SNA15-ELR. The combination of both RGD and SNA15 into the same ELR stimulated cell adhesion, proliferation, and differentiation, although at lower levels than those for every single moiety. These results suggest that biofunctionalization with SNA15-ELRs could modulate the cellular response to improve the osseointegration of Ti implants. Further investigation on the amount and distribution of RGD and SNA15 moieties in ELRs could improve cell adhesion, proliferation, and differentiation compared to the present study.

Poly (Ether-Ether-Ketone) for Biomedical Applications: From Enhancing Bioactivity to Reinforced-Bioactive Composites-An Overview

The global orthopedic market is forecasted to reach US$79.5 billion by the end of this decade. Factors driving the increase in this market are population aging, sports injury, road traffic accidents, and overweight, which justify a growing demand for orthopedic implants. Therefore, it is of utmost importance to develop bone implants with superior mechanical and biological properties to face the demand and improve patients' quality of life. Today, metallic implants still hold a dominant position in the global orthopedic implant market, mainly due to their superior mechanical resistance. However, their performance might be jeopardized due to the possible release of metallic debris, leading to cytotoxic effects and inflammatory responses in the body. Poly (ether-ether-ketone) (PEEK) is a biocompatible, high-performance polymer and one of the most prominent candidates to be used in manufacturing bone implants due to its similarity to the mechanical properties of bone. Unfortunately, the bioinert nature of PEEK culminates in its diminished osseointegration. Notwithstanding, PEEK's bioactivity can be improved through surface modification techniques and by the development of bioactive composites. This paper overviews the advantages of using PEEK for manufacturing implants and addresses the most common strategies to improve the bioactivity of PEEK in order to promote enhanced biomechanical performance.

Evaluation of the biocompability and corrosion activity of resorbable CaMgZnYbBAu alloys

Calcium-based alloys can be promising candidates for use as biodegradable implants because of attractive properties as mechanical, corrosive, and biocompatible. In the work, the biocompatibility authors discussed the results of the Ca₃₂Mg₁₂Zn₃₈Yb_18-xB_x (x = 0, 1, 2, 3 at.%) and Ca₃₂Mg₁₂Zn₃₈Yb_18-2xB_xAu_x (x = 1, 2 at.%) alloys. The tests were performed using a MTT assay. The corrosion behavior of such Ca-based alloys in PWE fluid at 37 °C was studied and compared with the results in Ringer's solution from previous works. Electrochemical tests were presented by open circuit potential and potentiodynamic curves. Different concentrations of boron and gold in the alloys caused changes in the corrosion results. The best corrosion resistance in PWE solution was observed for the Ca-based alloy with 2 at.% Au due to the lowest value of the corrosion current density (j_corr), equal to 10.6 µA·cm^-2. A slightly higher value of j_corr was obtained for the Ca₃₂Mg₁₂Zn₃₈Yb₁₅B₃ alloy with the lowest roughness values. The results of the cytotoxicity tests also showed that the alloy with 3 at.% boron was characterized by the highest cell viability. The investigation results discussed in the work allow us to suggest that the presented calcium alloys with 3 at.% of B, and 2 at.% of Au addition may be promising materials for the use in implantology.

Additively Manufactured Porous Ti6Al4V for Bone Implants: A Review

Ti-6Al-4V (Ti64) alloy is one of the most widely used orthopedic implant materials due to its mechanical properties, corrosion resistance, and biocompatibility nature. Porous Ti64 structures are gaining more research interest as bone implants as they can help in reducing the stress-shielding effect when compared to their solid counterpart. The literature shows that porous Ti64 implants fabricated using different additive manufacturing (AM) process routes, such as laser powder bed fusion (L-PBF) and electron beam melting (EBM) can be tailored to mimic the mechanical properties of natural bone. This review paper categorizes porous implant designs into non-gradient (uniform) and gradient (non-uniform) porous structures. Gradient porous design appears to be more promising for orthopedic applications due to its closeness towards natural bone morphology and improved mechanical properties. In addition, this paper outlines the details on bone structure and its properties, mechanical properties, fatigue behavior, multifunctional porous implant designs, current challenges, and literature gaps in the research studies on porous Ti64 bone implants.