Enhanced Osseointegration by the Hierarchical Micro-Nano Topography on Selective Laser Melting Ti-6Al-4V Dental Implants

Nanoscaled Titanium Oxide Layer Provokes Quick Osseointegration on 3D-Printed Dental Implants: A Domino Effect Induced by Hydrophilic Surface

Three-dimensional printing is a revolutionary strategy to fabricate dental implants. Especially, 3D-printed dental implants modified with nanoscaled titanium oxide layer (H-SLM) have impressively shown quick osseointegration, but the accurate mechanism remains elusive. Herein, we unmask a domino effect that the hydrophilic surface of the H-SLM facilitates blood wetting, enhances the blood shear rate, promotes blood clotting, and changes clot features for quick osseointegration. Combining computational fluid dynamic simulation and biological verification, we find a blood shear rate during blood wetting of the hydrophilic H-SLM 1.2-fold higher than that of the raw 3D-printed implant, which activates blood clot formation. Blood clots formed on the hydrophilic H-SLM demonstrate anti-inflammatory and pro-osteogenesis effects, leading to a 1.5-fold higher bone-to-implant contact and a 1.8-fold higher mechanical anchorage at the early stage of osseointegration. This mechanism deepens current knowledge between osseointegration speed and implant surface characteristics, which is instructive in surface nanoscaled modification of multiple 3D-printed intrabony implants.

Magnetically-actuated microcages for cells entrapment, fabricated by laser direct writing via two photon polymerization

The manipulation of biological materials at cellular level constitutes a sine qua non and provocative research area regarding the development of micro/nano-medicine. In this study, we report on 3D superparamagnetic microcage-like structures that, in conjunction with an externally applied static magnetic field, were highly efficient in entrapping cells. The microcage-like structures were fabricated using Laser Direct Writing via Two-Photon Polymerization (LDW via TPP) of IP-L780 biocompatible photopolymer/iron oxide superparamagnetic nanoparticles (MNPs) composite. The unique properties of LDW via TPP technique enabled the reproduction of the complex architecture of the 3D structures, with a very high accuracy i.e., about 90 nm lateral resolution. 3D hyperspectral microscopy was employed to investigate the structural and compositional characteristics of the microcage-like structures. Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy was used to prove the unique features regarding the morphology and the functionality of the 3D structures seeded with MG-63 osteoblast-like cells. Comparative studies were made on microcage-like structures made of IP-L780 photopolymer alone (i.e., without superparamagnetic properties). We found that the cell-seeded structures made by IP-L780/MNPs composite actuated by static magnetic fields of 1.3 T were 13.66 ± 5.11 folds (p < 0.01) more efficient in terms of cells entrapment than the structures made by IP-L780 photopolymer alone (i.e., that could not be actuated magnetically). The unique 3D architecture of the microcage-like superparamagnetic structures and their actuation by external static magnetic fields acted in synergy for entrapping osteoblast-like cells, showing a significant potential for bone tissue engineering applications.

Mechanical and Surface Characteristics of Selective Laser Melting-Manufactured Dental Prostheses in Different Processing Stages

Due to the expansion of the use of powder bed fusion metal additive technologies in the medical field, especially for the realization of dental prostheses, in this paper, the authors propose a comparative experimental study of the mechanical characteristics and the state of their microscale surfaces. The comparison was made from material considerations starting from two dental alloys commonly used to realize dental prostheses: Ni-Cr and Co-Cr, but also technologies for obtaining selective laser melting (SLM) and conventional casting. In addition, to compare the performances with the classical casting technology, for the dental prostheses obtained through SLM, the post-processing stage in which they are in a preliminary finishing and polished state was considered. Therefore, for the determination of important mechanical characteristics and the comparative study of dental prostheses, the indentation test was used, after which the hardness, penetration depths (maximum, permanent, and contact depth), contact stiffness, and contact surface were established, and for the determination of the microtopography of the surfaces, atomic force microscopy (AFM) was used, obtaining the local areal roughness parameters at the miniaturized scale-surface average roughness, root-mean-square roughness (RMS), and peak-to-peak values. Following the research carried out, several interesting conclusions were drawn, and the superiority of the SLM technology over the classic casting method for the production of dental prostheses in terms of some mechanical properties was highlighted. At the same time, the degree of finishing of dental prostheses made by SLM has a significant impact on the mechanical characteristics and especially the local roughness parameters on a miniaturized scale, and if we consider the same degree of finishing, no major differences are observed in the roughness parameters of the surfaces of the prostheses produced by different technologies.

Reduced Cell Adhesion on LightPLAS-Coated Implant Surfaces in a Three-Dimensional Bioreactor System

Most implants used in trauma surgery are made of steel and remain inside the body only temporarily. The strong tissue interaction of such implants sometimes creates problems with their explantation. Modified implant surfaces, which decrease tissue attachment, might allow an easier removal and therefore a better outcome. Such a modification must retain the implant function, and needs to be biocompatible and cost-effective. Here, we used a novel VUV-light (Vacuum-Ultraviolett)-based coating technology (LightPLAS) to generate coated stainless-steel plates. The tested LightPLAS coating only had an average thickness of around 335 nm, making it unlikely to interfere with implant function. The coated plates showed good biocompatibility according to ISO 10993-5 and ISO 10993-12, and reduced cell adhesion after four different time points in a 2D cell culture system with osteoblast-like MG-63 cells. Furthermore, we could show decreased cell adhesion in our 3D cell culture system, which mimics the fluid flow above the implant materials as commonly present in the in vivo environment. This new method of surface coating could offer extended options to design implant surfaces for trauma surgery to reduce cell adhesion and implant ingrowth. This may allow for a faster removal time, resulting in shorter overall operation times, thereby reducing costs and complication rates and increasing patient wellbeing.

Osseointegration in additive-manufactured titanium implants: A systematic review of animal studies on the need for surface treatment

The objective of the systematic review is to find an answer to a question: "Do surface treatments on titanium implants produced by additive manufacturing improve osseointegration, compared to untreated surfaces?". This review followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA 2020) and was registered in the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42022321351). Searches were performed in PubMed, Scopus, Science Direct, Embase, and Google Scholar databases on March 22nd, 2022. Articles were chosen in 2 steps by 2 blinded reviewers based on previously selected inclusion criteria: articles in animals that addressed the influence of surface treatments on osseointegration in implants produced by additive manufacturing. Articles were excluded that (1) did not use titanium surface, 2) that did not evaluate surface treatments, 3) that did not described osseointegration, 4) Studies with only in vitro analyses, clinical studies, systematic reviews, book chapters, short communications, conference abstracts, case reports and personal opinions.). 1003 articles were found and, after applying the eligibility criteria, 17 were used for the construction of this review. All included studies found positive osseointegration results from performing surface treatments on titanium. The risk of bias was analyzed using the SYRCLE assessment tool. Surface treatments are proposed to promote changes in the microstructure and composition of the implant surface to favor the adhesion of bone cells responsible for osseointegration. It is observed that despite the benefits generated by the additive manufacturing process in the microstructure of the implant surface, surface treatments are still indispensable, as they can promote more suitable characteristics for bone-implant integration. It can be concluded that the surface treatments evaluated in this systematic review, performed on implants produced by additive manufacturing, optimize osseointegration, as it allows the creation of a micro-nano-textured structure that makes the surface more hydrophilic and allows better contact bone-implant.

Modulation of MG-63 Osteogenic Response on Mechano-Bactericidal Micronanostructured Titanium Surfaces

Despite recent advances in the development of orthopedic devices, implant-related failures that occur as a result of poor osseointegration and nosocomial infection are frequent. In this study, we developed a multiscale titanium (Ti) surface topography that promotes both osteogenic and mechano-bactericidal activity using a simple two-step fabrication approach. The response of MG-63 osteoblast-like cells and antibacterial activity toward Pseudomonas aeruginosa and Staphylococcus aureus bacteria was compared for two distinct micronanoarchitectures of differing surface roughness created by acid etching, using either hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), followed by hydrothermal treatment, henceforth referred to as either MN-HCl or MN-H₂SO₄. The MN-HCl surfaces were characterized by an average surface microroughness (S_a) of 0.8 ± 0.1 μm covered by blade-like nanosheets of 10 ± 2.1 nm thickness, whereas the MN-H₂SO₄ surfaces exhibited a greater S_a value of 5.8 ± 0.6 μm, with a network of nanosheets of 20 ± 2.6 nm thickness. Both micronanostructured surfaces promoted enhanced MG-63 attachment and differentiation; however, cell proliferation was only significantly increased on MN-HCl surfaces. In addition, the MN-HCl surface exhibited increased levels of bactericidal activity, with only 0.6% of the P. aeruginosa cells and approximately 5% S. aureus cells remaining viable after 24 h when compared to control surfaces. Thus, we propose the modulation of surface roughness and architecture on the micro- and nanoscale to achieve efficient manipulation of osteogenic cell response combined with mechanical antibacterial activity. The outcomes of this study provide significant insight into the further development of advanced multifunctional orthopedic implant surfaces.

Micro/nano-modified titanium surfaces accelerate osseointegration via Rab7-dependent mitophagy

To achieve rapid and successful osseointegration of titanium (Ti) implants, the underlying mechanisms of surface modification-mediated bone metabolism need to be clarified. Given that the microenvironment surrounding Ti implants may be altered after implant insertion, mitophagy as a key control system for cellular homeostasis is most likely to regulate osseointegration. Recent findings suggest that PTEN-induced putative kinase 1 (Pink1)/Parkin-mediated mitophagy plays a key role in bone metabolism. Since the micro/nano-modified surfaces of Ti implants have been widely appreciated for osseointegration acceleration, we used two common micro/nano-modified techniques and demonstrated elevations of both the osteo-differentiation potential and Pink1/Parkin pathway of osteoblasts. Moreover, the Pink1/Parkin pathway exhibited an upward trend during osteoblast differentiation. However, when osteoblasts were treated with CCCP, a Pink1/Parkin inducer, the osteo-differentiation potential decreased. Our further study showed that the small GTPase Rab7, which was inhibited by CCCP, was essential for the Pink1/Parkin pathway. Upon Pink1 or Rab7 knockdown, the pro-osteogenic effect of micro/nano-modified Ti surfaces was significantly weakened. The present results demonstrated that Rab7 activation was essential for active mitophagy and osteogenesis. In addition, Rab7 was confirmed to mediate the process of autophagosome formation. Our findings provide novel insights into new targets for osseointegration promotion, regardless of Ti surface characteristics.

Advanced materials and technologies for oral diseases

Oral disease, as a class of diseases with very high morbidity, brings great physical and mental damage to people worldwide. The increasing burden and strain on individuals and society make oral diseases an urgent global health problem. Since the treatment of almost all oral diseases relies on materials, the rapid development of advanced materials and technologies has also promoted innovations in the treatment methods and strategies of oral diseases. In this review, we systematically summarized the application strategies in advanced materials and technologies for oral diseases according to the etiology of the diseases and the comparison of new and old materials. Finally, the challenges and directions of future development for advanced materials and technologies in the treatment of oral diseases were refined. This review will guide the fundamental research and clinical translation of oral diseases for practitioners of oral medicine.

Laser-Induced µ-Rooms for Osteocytes on Implant Surface: An In Vivo Study

Laser processing of dental implant surfaces is becoming a more widespread replacement for classical techniques due to its undeniable advantages, including control of oxide formation and structure and surface relief at the microscale. Thus, using a laser, we created several biomimetic topographies of various shapes on the surface of titanium screw-shaped implants to research their success and survival rates. A distinctive feature of the topographies is the presence of "µ-rooms", which are special spaces created by the depressions and elevations and are analogous to the µ-sized room in which the osteocyte will potentially live. We conducted the comparable in vivo study using dental implants with continuous (G-topography with µ-canals), discrete (S-topography with μ-cavities), and irregular (I-topography) laser-induced topographies. A histological analysis performed with the statistical method (with p-value less than 0.05) was conducted, which showed that G-topography had the highest BIC parameter and contained the highest number of mature osteocytes, indicating the best secondary stability and osseointegration.

Micro/Nanostructured Topography on Titanium Orchestrates Dendritic Cell Adhesion and Activation via β2 Integrin-FAK Signals

Background and Purpose

In clinical application of dental implants, the functional state of dendritic cells (DCs) has been suggested to have a close relationship with the implant survival rate or speed of osseointegration. Although microscale surfaces have a stable osteogenesis property, they also incline to trigger unfavorable DCs activation and threaten the osseointegration process. Nanoscale structures have an advantage in regulating cell immune response through orchestrating cell adhesion, indicating the potential of hierarchical micro/nanostructured surface in regulation of DCs’ activation without sacrificing the advantage of microscale topography.

Materials and Methods

Two micro/nanostructures were fabricated based on microscale rough surfaces through anodization or alkali treatment, the sand-blasted and acid-etched (SA) surface served as control. The surface characteristics, in vitro and in vivo DC immune reactions and β2 integrin-FAK signal expression were systematically investigated. The DC responses to different surface topographies after FAK inhibition were also tested.

Results

Both micro/nano-modified surfaces exhibited unique composite structures, with higher hydrophilicity and lower roughness compared to the SA surface. The DCs showed relatively immature functional states with round morphologies and significantly downregulated β2 integrin-FAK levels on micro/nanostructures. Implant surfaces with micro/nano-topographies also triggered lower levels of DC inflammatory responses than SA surfaces in vivo. The inhibited FAK activation effectively reduced the differences in topography-caused DC activation and narrowed the differences in DC activation among the three groups.

Conclusion

Compared to the SA surface with solely micro-scale topography, titanium surfaces with hybrid micro/nano-topographies reduced DC inflammatory response by influencing their adhesion states. This regulatory effect was accompanied by the modulation of β2 integrin-FAK signal expression. The β2 integrin-FAK-mediated adhesion plays a critical role in topography-induced DC activation, which represents a potential target for material–cell interaction regulation.

Strontium-doping promotes bone bonding of titanium implants in osteoporotic microenvironment

Osteoporosis is a major challenge to oral implants, and this study focused on improving the osseointegration ability of titanium (Ti) implants in osteoporosis environment via surface modification, including doping of strontium ion and preparation of nanoscale surface feature. Our previous studies have shown that strontium (Sr) ions can enhance osteogenic activity. Therefore, we aimed to comprehensively evaluate the effect of hydrothermal treatment of Sr-doped titanium implant coating on bone-binding properties in the microenvironment of osteoporosis in this study. We fabricated Sr-doped nanocoating (AHT-Sr) onto the surface of titanium implants via hydrothermal reaction. The rough Sr-doping had good biological functions and could apparently promote osteogenic differentiation of osteoporotic bone marrow mesenchymal stem cells (OVX-BMSCs). Most importantly, AHT-Sr significantly promoted bone integration in the osteoporosis environment. This study provides an effective approach to implant surface modification for better osseointegration in an osteoporotic environment.

Micro/nano topography of selective laser melting titanium inhibits osteoclastogenesis via mediation of macrophage polarization

Selective laser melting (SLM) titanium (Ti) implants have shown good prospects for personalized clinical application, but further research is necessary to develop stabilized long-term properties. Since surface modification has been proven bioactive for osseointegration, conventional Ti surface treatment technologies, including sandblasting/acid-etching (SLA) and sandblasting/alkali-heating (SAH), were applied to construct micro and micro/nano surfaces. The SAH group with netlike nano-structure topography exhibited appropriate surface roughness and high hydrophilicity, and as expected, the osseointegration capacities in vivo of the three groups were in order of SAH > SLA > SLM. Besides, both in vivo and in vitro studies revealed that the SLA- and SAH-treated SLM Ti implants significantly inhibited osteoclast activity of peri-implants. Considering the close associations between osteoclasts and macrophages, the effects of Ti surface topography on macrophage polarization were detected. The results showed that the SLA- and SAH-treated SLM Ti implants, especially the latter, had the capacity to promote macrophage polarization to the M2 phenotype. Moreover, the cell culture supernatants of M2 macrophages and RAW264.7 cells seeded on SLA- and SAH-treated SLM Ti surfaces had an adverse effect on osteoclastogenesis. Collectively, this study demonstrated that micro/nano topographies of SLM Ti implants were effective for osseointegration promotion, and their inhibition of osteoclastogenesis might be attributed to macrophage polarization. Our findings shed some light on clinical application of SLM Ti implants and also prove a specific association between macrophage polarization and osteoclastogenesis.

Study on Mechanism of Structure Angle on Microstructure and Properties of SLM-Fabricated 316L Stainless Steel

In this study, seven 316L stainless steel (316L SS) bulks with different angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) relative to a build substrate were built via selective laser melting (SLM). The influences of different angles on the metallography, microstructure evolution, tensile properties, and corrosion resistance of 316L SS were studied. The 0° sample showed the morphology of corrugated columnar grains, while the 90° sample exhibited equiaxed grains but with a strong <101> texture. The 60° sample had a good strength and plasticity: the tensile strength with 708 MPa, the yield strength with 588 MPa, and the elongation with 54.51%. The dislocation strengthening and grain refinement play a vital role in the mechanical properties for different anisotropy of the SLM-fabricated 316L SS. The 90° sample had greater toughness and corrosion resistance, owing to the higher volume fraction of low-angle grain boundaries and finer grains.

Polycrystalline diamond coating on 3D printed titanium scaffolds: Surface characterisation and foreign body response

Titanium-based implants are the leading material for orthopaedic surgery, due to their strength, versatility, fabrication via additive manufacturing and invoked biological response. However, the interface between the implant and the host tissue requires improvement to better integrate the implant material and mitigate foreign body response. The interface can be manipulated by changing the surface energy, chemistry, and topography of the Titanium-based implant. Recently, polycrystalline diamond (PCD) has emerged as an exciting coating material for 3D printed titanium scaffolds showing enhanced mammalian cell functions while inhibiting bacterial attachment in vitro. In this study, we performed in-depth characterisation of PCD coatings investigating the surface topography, thickness, surface energy, and compared its foreign body response in vivo with uncoated titanium scaffold. Coating PCD onto titanium scaffolds resulted in a similar microscale surface roughness (RMS_(PCD-coated) = 24 μm; RMS_(SLM-Ti) = 28 μm), increased nanoscale roughness (RMS_(PCD-coated) = 35 nm; RMS_(SLM-Ti) = 66 nm) and a considerable decrease in surface free energy (E_(PCD-coated) = 4 mN m^-1; E_(SLM-Ti) = 16 mN m^-1). These surface property changes were supported by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy as corresponding to observed surface chemistry changes induced by the coating. The underlying mechanism of how the diamond coatings chemical and physical properties changes the wettability of implants was examined. In vivo, the coated scaffolds induced similar level of fibrous encapsulation with uncoated scaffolds. This study thus provides further insight into the physicochemical characteristics of PCD coatings, adding evidence to the promising potential of PCD-coatings of medical implants.

Porous Titanium by Additive Manufacturing: A Focus on Surfaces for Bone Integration

Additive manufacturing (AM) is gaining increasing interest for realization of customized porous titanium constructs for biomedical applications and, in particular, for bone substitution. As first, the present review gives a short introduction on the techniques used for additive manufacturing of Ti/Ti-Alloys (Direct Energy Deposition—DED, Selective Laser Melting—SLM and Electron Beam Melting—EBM) and on the main bulk properties of additively manufactured titanium porous structures. Then, it discusses the main advancements in surface modifications of additively manufactured titanium constructs for bone contact applications. Even if specific surface modifications of constructs from AM are currently not widely explored, it is a critical open issue for application in biomedical implants. Some thermal, chemical, electrochemical, and hydrothermal treatments as well as different coatings are here described. The main aim of these treatments is the development of surface micro/nano textures, specific ion release, and addition of bioactivity to induce bone bonding and antibacterial activity. Physicochemical characterizations, in vitro bioactivity tests, protein absorption, in vitro (cellular/bacterial) and in vivo tests reported in the literature for bare and surface modified AM Ti-based constructs are here reviewed. Future perspectives for development of innovative additively manufactured titanium implants are also discussed.

Novel dental implant modifications with two-staged double benefits for preventing infection and promoting osseointegration in vivo and in vitro

Peri-implantitis are a major problem causing implant failure these days. Accordingly, anti-infection during the early stage and subsequent promotion of osseointegration are two main key factors to solve this issue. Micro-arc oxidation (MAO) treatment is a way to form an oxidation film on the surface of metallic materials. The method shows good osteogenic properties but weak antibacterial effect. Therefore, we developed combined strategies to combat severe peri-implantitis, which included the use of a novel compound, PD, comprising dendrimers poly(amidoamine) (PAMAM) loading dimethylaminododecyl methacrylate (DMADDM) as well as MAO treatment. Here, we explored the chemical properties of the novel compound PD, and proved that this compound was successfully synthesized, with the loading efficiency and encapsulation efficiency of 23.91% and 31.42%, respectively. We further report the two-stage double benefits capability of PD + MAO: (1) in the first stage, PD + MAO could decrease the adherence and development of biofilms by releasing DMADDM in the highly infected first stage after implant surgery both in vitro and in vivo; (2) in the second stage, PD + MAO indicated mighty anti-infection and osteoconductive characteristics in a rat model of peri-implantitis in vivo. This study first reports the two-staged, double benefits of PD + MAO, and demonstrates its potential in clinical applications for inhibiting peri-implantitis, especially in patients with severe infection risk.