One-Step Synthesis of Versatile Antimicrobial Nano-Architected Implant Coatings for Hard and Soft Tissue Healing

Microbial corrosion of metallic biomaterials in the oral environment

A wide variety of microorganisms have been closely linked to metal corrosion in the form of adherent surface biofilms. Biofilms allow the development and maintenance of locally corrosive environments and/or permit direct corrosion including pitting corrosion. The presence of numerous genetically distinct microorganisms in the oral environment poses a threat to the integrity and durability of the surface of metallic prostheses and implants used in routine dentistry. However, the association between oral microorganisms and specific corrosion mechanisms is not clear. It is of practical importance to understand how microbial corrosion occurs and the associated risks to metallic materials in the oral environment. This knowledge is also important for researchers and clinicians who are increasingly concerned about the biological activity of the released corrosion products. Accordingly, the main goal was to comprehensively review the current literature regarding oral microbiologically influenced corrosion (MIC) including characteristics of biofilms and of the oral environment, MIC mechanisms, corrosion behavior in the presence of oral microorganisms and potentially mitigating technologies. Findings included that oral MIC has been ascribed mostly to aggressive metabolites secreted during microbial metabolism (metabolite-mediated MIC). However, from a thermodynamic point of view, extracellular electron transfer mechanisms (EET-MIC) through pili or electron transfer compounds cannot be ruled out. Various MIC mitigating methods have been demonstrated to be effective in short term, but long term evaluations are necessary before clinical applications can be considered. Currently most in-vitro studies fail to simulate the complexity of intraoral physiological conditions which may either reduce or exacerbate corrosion risk, which must be addressed in future studies. STATEMENT OF SIGNIFICANCE: A thorough analysis on literature regarding oral MIC (microbiologically influenced corrosion) of biomedical metallic materials has been carried out, including characteristics of oral environment, MIC mechanisms, corrosion behaviors in the presence of typical oral microorganisms and potential mitigating methods (materials design and surface design). There is currently a lack of mechanistic understanding of oral MIC which is very important not only to corrosion researchers but also to dentists and clinicians. This paper discusses the significance of biofilms from a biocorrosion perspective and summarizes several aspects of MIC mechanisms which could be caused by oral microorganisms. Oral MIC has been closely associated with not only the materials research but also the dental/clinical research fields in this work.

Enhancement of Biocompatibility of High-Transparency Zirconia Abutments with Human Gingival Fibroblasts via Cold Atmospheric Plasma Treatment: An In Vitro Study

The objective of this study was to explore the effects of cold atmospheric plasma (CAP) treatment on the biological behavior of human gingival fibroblasts (HGFs) cultured on the surface of high-transparency zirconia. Two types of zirconia, 3Y-ZTP and 4Y-PSZ, were subjected to a CAP treatment for various treatment durations. Analyses of the physical and chemical properties of 3Y-ZTP and 4Y-PSZ were conducted using scanning electron microscopy, contact angle measurements, and X-ray photoelectron spectroscopy, both before and after CAP treatment. The biological responses of HGFs on both surfaces were assessed using CCK-8 assay, confocal laser scanning microscopy, and real-time PCR. Initially, the oxygen and hydroxyl contents on the surface of 4Y-PSZ exceeded those on 3Y-ZTP. CAP treatment enhanced the surface hydrophilicity and the reactive oxygen species (ROS) content of 4Y-PSZ, while not altering the surface morphology. After CAP treatment, HGFs' adhesion on 4Y-PSZ was superior, with more pronounced effects compared to 3Y-ZTP. Notably, HGFs counts and the expression of adhesion-related genes on 4Y-PSZ peaked following the CAP exposures for 30 s and 60 s. Consequently, this study demonstrates that, following identical CAP treatments, 4Y-PSZ is more effective in promoting HGFs adhesion compared to traditional 3Y-ZTP zirconia.

Surface-Engineered Titanium with Nanoceria to Enhance Soft Tissue Integration Via Reactive Oxygen Species Modulation and Nanotopographical Sensing

The design of implantable biomaterials involves precise tuning of surface features because the early cellular fate on such engineered surfaces is highly influenced by many physicochemical factors [roughness, hydrophilicity, reactive oxygen species (ROS) responsiveness, etc.]. Herein, to enhance soft tissue integration for successful implantation, Ti substrates decorated with uniform layers of nanoceria (Ce), called Ti@Ce, were optimally developed by a simple and cost-effective in situ immersion coating technique. The characterization of Ti@Ce shows a uniform Ce distribution with enhanced roughness (∼3-fold increase) and hydrophilicity (∼4-fold increase) and adopted ROS-scavenging capacity by nanoceria coating. When human gingival fibroblasts were seeded on Ti@Ce under oxidative stress conditions, Ti@Ce supported cellular adhesion, spreading, and survivability by its cellular ROS-scavenging capacity. Mechanistically, the unique nanocoating resulted in higher expression of amphiphysin (a nanotopology sensor), paxillin (a focal adhesion protein), and cell adhesive proteins (collagen-1 and fibronectin). Ti@Ce also led to global chromatin condensation by decreasing histone 3 acetylation as an early differentiation feature. Transcriptome analysis by RNA sequencing confirmed the chromatin remodeling, antiapoptosis, antioxidant, cell adhesion, and TGF-β signaling-related gene signatures in Ti@Ce. As key fibroblast transcription (co)factors, Ti@Ce promotes serum response factor and MRTF-α nucleus localization. Considering all of this, it is proposed that the surface engineering approach using Ce could improve the biological properties of Ti implants, supporting their functioning at soft tissue interfaces and utilization as a bioactive implant for clinical conditions such as peri-implantitis.

Hydroxyapatite-Based Coatings on Silicon Wafers and Printed Zirconia

Dental surgery needs a biocompatible implant design that can ensure both osseointegration and soft tissue integration. This study aims to investigate the behavior of a hydroxyapatite-based coating, specifically designed to be deposited onto a zirconia substrate that was intentionally made porous through additive manufacturing for the purpose of reducing the cost of material. Layers were made via sol-gel dip coating by immersing the porous substrates into solutions of hydroxyapatite that were mixed with polyethyleneimine to improve the adhesion of hydroxyapatite to the substrate. The microstructure was determined by using X-ray diffraction, which showed the adhesion of hydroxyapatite; and atomic force microscopy was used to highlight the homogeneity of the coating repartition. Thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy showed successful, selective removal of the polymer and a preserved hydroxyapatite coating. Finally, scanning electron microscopy pictures of the printed zirconia ceramics, which were obtained through the digital light processing additive manufacturing method, revealed that the mixed coating leads to a thicker, more uniform layer in comparison with a pure hydroxyapatite coating. Therefore, homogeneous coatings can be added to porous zirconia by combining polyethyleneimine with hydroxyapatite. This result has implications for improving global access to dental care.

How Can Imbalance in Oral Microbiota and Immune Response Lead to Dental Implant Problems?

Dental implantology is one of the most dynamically developing fields of dentistry, which, despite developing clinical knowledge and new technologies, is still associated with many complications that may lead to the loss of the implant or the development of the disease, including peri-implantitis. One of the reasons for this condition may be the fact that dental implants cannot yield a proper osseointegration process due to the development of oral microbiota dysbiosis and the accompanying inflammation caused by immunological imbalance. This study aims to present current knowledge as to the impact of oral microflora dysbiosis and deregulation of the immune system on the course of failures observed in dental implantology. Evidence points to a strong correlation between these biological disturbances and implant complications, often stemming from improper osseointegration, pathogenic biofilms on implants, as well as an exacerbated inflammatory response. Technological enhancements in implant design may mitigate pathogen colonization and inflammation, underscoring implant success rates.

Modification of titanium orthopedic implants with bioactive glass: a systematic review of in vivo and in vitro studies

Bioactive glasses (BGs) are ideal biomaterials in the field of bio-restoration due to their excellent biocompatibility. Titanium alloys are widely used as a bone graft substitute material because of their excellent corrosion resistance and mechanical properties; however, their biological inertness makes them prone to clinical failure. Surface modification of titanium alloys with bioactive glass can effectively combine the superior mechanical properties of the substrate with the biological properties of the coating material. In this review, the relevant articles published from 2013 to the present were searched in four databases, namely, Web of Science, PubMed, Embase, and Scopus, and after screening, 49 studies were included. We systematically reviewed the basic information and the study types of the included studies, which comprise in vitro experiments, animal tests, and clinical trials. In addition, we summarized the applied coating technologies, which include pulsed laser deposition (PLD), electrophoretic deposition, dip coating, and magnetron sputtering deposition. The superior biocompatibility of the materials in terms of cytotoxicity, cell activity, hemocompatibility, anti-inflammatory properties, bioactivity, and their good bioactivity in terms of osseointegration, osteogenesis, angiogenesis, and soft tissue adhesion are discussed. We also analyzed the advantages of the existing materials and the prospects for further research. Even though the current research status is not extensive enough, it is still believed that BG-coated Ti implants have great clinical application prospects.

Influence of surface nanotopography and wettability on early phases of peri-implant soft tissue healing: an in-vivo study in dogs

BACKGROUND

It is well established that nanotopography and wettability of implant surfaces contribute to osseointegration and long-term implant success. However, the effects of a hydrogenated surface with nanotubular and superhydrophilic properties on peri-implant soft tissue remain unclear. This study was designed to study the impact of a modified abutment surface on early soft tissue integration compared with a machined surface.

METHODS

Thirty-six implants were placed at the bone level in the bilateral mandible of six beagles, followed by healing abutments belonging to the standard machined Ti-6Al-4V alloy abutments (TC4-M), anodized abutments with nanotubes (TC4-Nano), and hydrogenated abutments (TC4-H/Nano) groups, which were randomly screwed to the implants. After two and four weeks of wound healing, the animals were euthanized for histological evaluation.

RESULTS

A superhydrophilic nanotubular surface developed on the hydrogenated abutment. Histological and histometric analyses revealed similar peri-implant soft tissue healing and dimensions for the three types of abutments at two and four weeks. Connective tissue (CT) length was longer around TC4-H/Nano abutments compared with standard abutments; however, the differences were not statistically significant. Moreover, collagen fibers in the TC4-H/Nano group extended and were attached perpendicularly to the superhydrophilic surface.

CONCLUSIONS

Our results revealed that the soft tissue interface adjacent to the hydrogenated abutment is comparable to that of the machined abutment. A tendency of increased CT length and perpendicular collagen fibers was observed around the modified abutment. This study suggests that nanotubular/superhydrophilic surfaces could be a promising modification to enhance soft tissue sealing. However, comprehensive studies should be conducted to evaluate the peri-implant soft tissue around the modified abutment immunohistochemically, histopathologically, and clinically.

Construction of a Localized and Long-Acting CCN2 Delivery System on Percutaneous Ti Implant Surfaces for Enhanced Soft-Tissue Integration

Soft-tissue integration (STI) plays an essential role in the long-term success of percutaneous Ti implants since it acts as a biological barrier that protects the soft and hard tissue around implants. Surface modification of Ti implants with drug-release properties to achieve soft-tissue regeneration has been proven to be effective in STI. However, the short-acting effect caused by the uncontrolled drug release of the topical delivery system limits long-term STI enhancement. Herein, a long-acting protein delivery system for Ti implants that involved micro-arc oxidation of Ti surfaces (MAO-Ti) and localized immobilization of cellular communication network factor 2 (CCN2) bearing mesoporous silica nanoparticles (MSNs) on MAO-Ti was prepared, namely, CCN2@MSNs-Ti. The CCN2 release study of CCN2@MSNs-Ti demonstrated a sustained-release profile for 21 days, which was able to maintain long-term stable STI. In addition, in vitro cell behavior evaluation results indicated that CCN2@MSNs-Ti could promote the STI-related biological response of human dermal fibroblasts via the FAK-MAPK pathway. More importantly, the system could effectively enhance STI after 4 weeks and proinflammatory factors in the soft tissue decreased significantly in a rat model of implantation. These results denote that CCN2@MSNs-Ti showed an appealing application prospect for enhanced STI around transcutaneous Ti implants, which would ultimately result in an increased success rate of percutaneous Ti implants.

Balancing the antibacterial and osteogenic effects of double-layer TiO2 nanotubes loaded with silver nanoparticles for the osseointegration of implants

The improvement of Ag nanoparticles (AgNPs), in particular, loaded titania nanotubes, includes not only the antibacterial effect but also balancing the side effects from the antibacterial effect and osteogenesis properties, which can lead to an increased success rate of implants. Herein, based on the various needs of the graft to inhibit bacteria at different stages in vivo, we used a special osteogenic honeycomb-like "large tube over small tube" double-layered nanotube structure and created ultra-small-sized silver nanoparticles uniformly loaded on the surface and the interior of double-layer nanotubes by an optimized sputter coating method to ensure the time-dependent controllable release of antibacterial Ag ions from grafts and achieve the balance of the antibacterial effect and osteogenesis properties. The release of Ag⁺ from DNT-Ag8 was determined by inductively coupled plasma spectrometry. The release rate of Ag was slow; it was 30% on the first day and plateaued by the 19th day. Porphyromonas gingivalis adhesion and live bacteria were less abundant on the surface of DNT-Ag8, reaching an antibacterial efficiency of 55.6% in vitro. DNT-Ag8 shows a significantly higher antibacterial effect in a rat model infected with Staphylococcus aureus. An in vitro study demonstrated that DNT-Ag8 had no adverse effects on the adhesion, viability, proliferation, ALP staining, or activity assays of rat BMSCs. In contrast, it increased the expression of osteogenic genes. In vivo, DNT-Ag8 promoted bone-implant osseointegration in a beagle mandibular tooth loss model. This study demonstrated that the uniform loading of small-diameter silver nanoparticles using a honeycomb bilayer nanotube template structure is a promising method for modifying titanium surfaces to improve both bacteriostasis and osseointegration.

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.

Introducing Nanozymes: New Horizons in Periodontal and Dental Implant Care

The prevalence of periodontal and peri-implant diseases has been increasing worldwide and has gained a lot of attention. As multifunctional nanomaterials with enzyme-like activity, nanozymes have earned a place in the biomedical field. In periodontics and implantology, nanozymes have contributed greatly to research on maintaining periodontal health and improving implant success rates. To highlight this progress, we review nanozymes for antimicrobial therapy, anti-inflammatory therapy, tissue regeneration promotion, and synergistic effects in periodontal and peri-implant diseases. The future prospects of nanozymes in periodontology and implantology are also discussed along with challenges.

Host-microbiome interactions regarding peri-implantitis and dental implant loss

In the last decades, the ortho-aesthetic-functional rehabilitation had significant advances with the advent of implantology. Despite the success in implantology surgeries, there is a percentage of failures mainly due to in loco infections, through bacterial proliferation, presence of fungi and biofilm formation, originating peri-implantitis. In this sense, several studies have been conducted since then, seeking answers to numerous questions that remain unknown. Thus, the present work aims to discuss the interaction between host-oral microbiome and the development of peri-implantitis. Peri-implantitis was associated with a diversity of bacterial species, being Porphiromonas gingivalis, Treponema denticola and Tannerella forsythia described in higher proportion of peri-implantitis samples. In a parallel role, the injury of peri-implant tissue causes an inflammatory response mediated by activation of innate immune cells such as macrophages, dendritic cells, mast cells, and neutrophils. In summary, the host immune system activation may lead to imbalance of oral microbiota, and, in turn, the oral microbiota dysbiosis is reported leading to cytokines, chemokines, prostaglandins, and proteolytic enzymes production. These biological processes may be responsible for implant loss.

Advances and Prospects in Antibacterial-Osteogenic Multifunctional Dental Implant Surface

In recent years, dental implantation has become the preferred protocol for restoring dentition defects. Being the direct contact between implant and bone interface, osseointegration is the basis for implant exerting physiological functions. Nevertheless, biological complications such as insufficient bone volume, poor osseointegration, and postoperative infection can lead to implant failure. Emerging antibacterial-osteogenic multifunctional implant surfaces were designed to make up for these shortcomings both during the stage of forming osseointegration and in the long term of supporting the superstructure. In this mini-review, we summarized the recent antibacterial-osteogenic modifications of the dental implant surface. The effects of these modifications on biological performance like soft tissue integration, bone osteogenesis, and immune response were discussed. In addition, the clinical findings and prospects of emerging antibacterial-osteogenic implant materials were also discussed.

Material priority engineered metal-polyphenol networks: mechanism and platform for multifunctionalities

Engineering the surface of materials with desired multifunctionalities is an effective way to fight against multiple adverse factors during tissue repair process. Recently, metal-polyphenol networks (MPNs) have gained increasing attention because of their rapid and simple deposition process onto various substrates (silicon, quartz, gold and polypropylene sheets, etc.). However, the coating mechanism has not been clarified, and multifunctionalized MPNs remain unexplored. Herein, the flavonoid polyphenol procyanidin (PC) was selected to form PC-MPN coatings with Fe³⁺, and the effects of different assembly parameters, including pH, molar ratio between PC and Fe³⁺, and material priority during coating formation, were thoroughly evaluated. We found that the material priority (addition sequence of PC and Fe³⁺) had a great influence on the thickness of the formed PC-MPNs. Various surface techniques (e.g., ultraviolet–visible spectrophotometry, quartz crystal microbalance, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy) were used to investigate the formation mechanism of PC-MPNs. Then PC-MPNs were further engineered with multifunctionalities (fastening cellular attachment in the early stage, promoting long-term cellular proliferation, antioxidation and antibacterial activity). We believe that these findings could further reveal the coating formation mechanism of MPNs and guide the future design of MPN coatings with multifunctionalities, thereby greatly broadening their application prospects, such as in sensors, environments, drug delivery, and tissue engineering.

Influence of Ceria Addition on Crystallization Behavior and Properties of Mesoporous Bioactive Glasses in the SiO2–CaO–P2O5–CeO2System

Knowledge of the crystallization stability of bioactive glasses (BGs) is a key factor in developing porous scaffolds for hard tissue engineering. Thus, the crystallization behavior of three mesoporous bioactive glasses (MBGs) in the 70SiO₂-(26-x)CaO-4P₂O₅-xCeO₂ system (x stands for 0, 1 and 5 mol. %, namely MBG(0/1/5)Ce), prepared using the sol–gel method coupled with the evaporation-induced self-assembly method (EISA), was studied. A thermal analysis of the multiple-component crystallization exotherms from the DSC scans was performed using the Kissinger method. The main crystalline phases of Ca₅(PO₄)2.823(CO₃)_0.22O, CaSiO₃ and CeO₂ were confirmed to be generated by the devitrification of the MBG with 5% CeO₂, MBG5Ce. Increasing the ceria content triggered a reduction in the first crystallization temperature while ceria segregation took place. The amount of segregated ceria of the annealed MBG5Ce decreased as the annealing temperature increased. The optimum processing temperature range to avoid the crystallization of the MBG(0/1/5)Ce powders was established.

Titanium Nanobowl-Based Nest-Like Nanofiber Structure Prepared at Room Temperature and Pressure Promotes Osseointegration of Beagle Implants

Nest-like nanofiber structures have potential applications in surface modifications of titanium implants. In this study, nest-like nanofiber structures were prepared on a titanium surface at room temperature and pressure by using the nanobowl template-assisted method combined with alkali etching. The characterization and biocompatibility of this material were analyzed by cellular adhesion, death, CCK-8, ALP, and RT-PCR assays in vitro, and osseointegration was evaluated by micro-CT and fluorescent labeling in vivo. The results showed that this nest-like nanofiber structure has a firmer and asperate surface than nanotubes, which leads to better cellular adhesion, proliferation, and differentiation capacity. In a beagle alveolar bone implant model, the nest-like nanofiber structure showed a better osseointegration capacity. In conclusion, this nest-like nanofiber structure has potential applications in dental implantology.