Mechanical and in vitro biological performances of hydroxyapatite-carbon nanotube composite coatings deposited on Ti by aerosol deposition

There Are over 60 Ways to Produce Biocompatible Calcium Orthophosphate (CaPO4) Deposits on Various Substrates

A The present overview describes various production techniques for biocompatible calcium orthophosphate (abbreviated as CaPO4) deposits (coatings, films and layers) on the surfaces of various types of substrates to impart the biocompatible properties for artificial bone grafts. Since, after being implanted, the grafts always interact with the surrounding biological tissues at the interfaces, their surface properties are considered critical to clinical success. Due to the limited number of materials that can be tolerated in vivo, a new specialty of surface engineering has been developed to desirably modify any unacceptable material surface characteristics while maintaining the useful bulk performance. In 1975, the development of this approach led to the emergence of a special class of artificial bone grafts, in which various mechanically stable (and thus suitable for load-bearing applications) implantable biomaterials and artificial devices were coated with CaPO4. Since then, more than 7500 papers have been published on this subject and more than 500 new publications are added annually. In this review, a comprehensive analysis of the available literature has been performed with the main goal of finding as many deposition techniques as possible and more than 60 methods (double that if all known modifications are counted) for producing CaPO4 deposits on various substrates have been systematically described. Thus, besides the introduction, general knowledge and terminology, this review consists of two unequal parts. The first (bigger) part is a comprehensive summary of the known CaPO4 deposition techniques both currently used and discontinued/underdeveloped ones with brief descriptions of their major physical and chemical principles coupled with the key process parameters (when possible) to inform readers of their existence and remind them of the unused ones. The second (smaller) part includes fleeting essays on the most important properties and current biomedical applications of the CaPO4 deposits with an indication of possible future developments.

A comprehensive review of properties of the biocompatible thin films on biodegradable Mg alloys

Magnesium (Mg) and its alloys have attracted attention as biodegradable materials for biomedical applications owing to their mechanical properties being comparable to that of bone. Mg is a vital trace element in many enzymes and thus forms one of the essential factors for human metabolism. However, before being used in biomedical applications, the early stage or fast degradation of Mg and its alloys in the physiological environment should be controlled. The degradation of Mg alloys is a critical criterion that can be controlled by a surface modification which is an effective process for conserving their desired properties. Different coating methods have been employed to modify Mg surfaces to provide good corrosion resistance and biocompatibility. This review aims to provide information on different coatings and discuss their physical and biological properties. Finally, the current withstanding challenges have been highlighted and discussed, followed by shedding some light on future perspectives.

Corrosion, mechanical and bioactivity properties of HA-CNT nanocomposite coating on anodized Ti6Al4V alloy

Hydroxyapatite-carbon nanotubes (HA-CNTs) nanocomposite coating was applied by electrophoretic method on anodized Ti alloy to investigate its stability in simulated body fluid (SBF). The biocoating was characterized by using scanning electron microscope (SEM) for microstructure, X-ray diffraction (XRD) for crystallography. The effect of CNTs concentration on the coating properties was also investigated and found out that CNTs up to 5% has various improving effect on the system. It increased corrosion resistance and adhesion of the coating to the substrate and decreased the number of cracks on the coating. The results of the in vitro test showed that the cell viability increased with increasing the concentration of CNTs to 3 wt.% CNTs. Graphical abstract.

Latest Trends in Surface Modification for Dental Implantology: Innovative Developments and Analytical Applications

An increase in the world population and its life expectancy, as well as the ongoing concern about our physical appearance, have elevated the relevance of dental implantology in recent decades. Engineering strategies to improve the survival rate of dental implants have been widely investigated, focusing on implant material composition, geometry (usually guided to reduce stiffness), and interface surrounding tissues. Although efforts to develop different implant surface modifications are being applied in commercial dental prostheses today, the inclusion of surface coatings has gained special interest, as they can be tailored to efficiently enhance osseointegration, as well as to reduce bacterial-related infection, minimizing peri-implantitis appearance and its associated risks. The use of biomaterials to replace teeth has highlighted the need for the development of reliable analytical methods to assess the therapeutic benefits of implants. This literature review considers the state-of-the-art strategies for surface modification or coating and analytical methodologies for increasing the survival rate for teeth restoration.

Cytotoxicity and Ion Release of Functionally Graded Al₂O₃- Ti Orthopedic Biomaterial

The aim of this study was to evaluate the biocompatibility of Al2O3-Ti functionally graded material (FGM) successfully fabricated by Spark Plasma Sintering (SPS) technology, and to compare with pure Ti and alumina. Pre-osteoblast MC3T3-E1 cells were used to examine cell viability, proliferation and differentiation using lactate dehydrogenase (LDH) cytotoxicity detection kit, MTT assay and Alkaline Phosphatase (ALP) colorimetric test at different time points. Furthermore, ion release from the materials into the culture medium was assessed. The results showed cell viability over 80% for FGM and alumina which dismissed any cytotoxicity risk due to materials or manufacturing. The results of MTT tests identified superiority of FGM than Ti and alumina, particularly in late proliferation. Nevertheless, in cell differentiation, all materials performed similarly with no statistical differences. Furthermore, it was indicated that Ti had no ion release, while alumina had small amount of Al ion dissolution. FGM, however, had more ions detachment, particularly Al ions.

Emerging zero-dimensional to four-dimensional biomaterials for bone regeneration

Bone is one of the most sophisticated and dynamic tissues in the human body, and is characterized by its remarkable potential for regeneration. In most cases, bone has the capacity to be restored to its original form with homeostatic functionality after injury without any remaining scarring. Throughout the fascinating processes of bone regeneration, a plethora of cell lineages and signaling molecules, together with the extracellular matrix, are precisely regulated at multiple length and time scales. However, conditions, such as delayed unions (or nonunion) and critical-sized bone defects, represent thorny challenges for orthopedic surgeons. During recent decades, a variety of novel biomaterials have been designed to mimic the organic and inorganic structure of the bone microenvironment, which have tremendously promoted and accelerated bone healing throughout different stages of bone regeneration. Advances in tissue engineering endowed bone scaffolds with phenomenal osteoconductivity, osteoinductivity, vascularization and neurotization effects as well as alluring properties, such as antibacterial effects. According to the dimensional structure and functional mechanism, these biomaterials are categorized as zero-dimensional, one-dimensional, two-dimensional, three-dimensional, and four-dimensional biomaterials. In this review, we comprehensively summarized the astounding advances in emerging biomaterials for bone regeneration by categorizing them as zero-dimensional to four-dimensional biomaterials, which were further elucidated by typical examples. Hopefully, this review will provide some inspiration for the future design of biomaterials for bone tissue engineering.

Effect of Nanostructures on the Properties of Glass Ionomer Dental Restoratives/Cements: A Comprehensive Narrative Review

Overall perspective of nanotechnology and reinforcement of dental biomaterials by nanoparticles has been reported in the literature. However, the literature regarding the reinforcement of dental biomaterials after incorporating various nanostructures is sparse. The present review addresses current developments of glass ionomer cements (GICs) after incorporating various metallic, polymeric, inorganic and carbon-based nanostructures. In addition, types, applications, and implications of various nanostructures incorporated in GICs are discussed. Most of the attempts by researchers are based on the laboratory-based studies; hence, it warrants long-term clinical trials to aid the development of suitable materials for the load bearing posterior dentition. Nevertheless, a few meaningful conclusions are drawn from this substantial piece of work; they are as follows: (1) most of the nanostructures are likely to enhance the mechanical strength of GICs; (2) certain nanostructures improve the antibacterial activity of GICs against the cariogenic bacteria; (3) clinical translation of these promising outcomes are completely missing, and (4) the nanostructured modified GICs could perform better than their conventional counterparts in the load bearing posterior dentition.

Osteoblastic cell response to Al2O3-Ti composites as bone implant materials

Introduction: Alumina-titanium (Al₂O₃-Ti) composites with enhanced mechanical and corrosion properties have been recently developed for potential applications in orthopaedics and hard tissue replacements. However, before any clinical use, their interactions with biological environment must be examined. Methods: The aim of this study, therefore, was to assess the biocompatibility of three Al₂O₃-Ti composites having 25, 50, and 75 volume percentages of titanium. These materials were made by spark plasma sintering (SPS), and MC3T3-E1 cells were cultured onto the sample discs to evaluate the cell viability, proliferation, differentiation, mineralization, and adhesion. Furthermore, the apatite formation ability and wettability of the composites were analysed. Pure Ti (100Ti) and monolithic Al₂O₃ (0Ti) were also fabricated by SPS and biological characteristics of the composites were compared with them. Results: The results showed that cell viability to 75Ti (95.0%), 50Ti (87.3%), and 25Ti (63.9%) was superior when compared with 100Ti (42.7%). Pure Al₂O₃ also caused very high cell viability (89.9%). Furthermore, high cell proliferation was seen at early stage for 50Ti, while the cells exposed to 75Ti proliferated more at late stages. Cell differentiation was approximately equal between different groups, and increased by time. Matrix mineralization was higher on the composite surfaces rather than on 0Ti and 100Ti. Moreover, the cells adhered differently to the surfaces of different biomaterials where more spindle-shaped configuration was found on 100Ti, slightly enlarged cells with dendritic shape and early pseudopodia were observed on 75Ti, and more enlarged cells with long dendritic extensions were found on 0Ti, 25Ti, and 50Ti. The results of EDS analysis showed that both Ca and P deposited on the surfaces of all materials, after 20 days of immersion in SBF. Conclusion: Our in-vitro findings demonstrated that the 75Ti, 50Ti, and 25Ti composites have high potential to be used as load-bearing orthopedic materials.

Dental Applications of Carbon Nanotubes

Glass ionomer cements and resin-based composites are promising materials in restorative dentistry. However, their limited mechanical properties and the risk of bulk/marginal fracture compromise their lifespan. Intensive research has been conducted to understand and develop new materials that can mimic the functional behavior of the oral cavity. Nanotechnological approaches have emerged to treat oral infections and become a part of scaffolds for tissue regeneration. Carbon nanotubes are promising materials to create multifunctional platforms for dental applications. This review provides a comprehensive survey of and information on the status of this state-of-the-art technology and describes the development of glass ionomers reinforced with carbon nanotubes possessing improved mechanical properties. The applications of carbon nanotubes in drug delivery and tissue engineering for healing infections and lesions of the oral cavity are also described. The review concludes with a summary of the current status and presents a vision of future applications of carbon nanotubes in the practice of dentistry.

Investigation of the structure and compressive strength of a bioceramic root canal sealer reinforced with nanomaterials

OBJECTIVES

A root canal sealer that can increase the resistance of endodontically treated teeth to compressive strength would be of great advantage. The purpose of this study is to use three different nanoparticles: multi-walled carbon nanotubes (MWCNTs), Titanium carbides (TC), and Boron nitrides (BN) into a bioceramic adhesive root canal sealer; BioRoot™ RCS, in an attempt to improve its structural and compressive strength properties.

METHODS

Three composites of two weight fractions (1- and 2-wt.%) were produced by mixing each nanomaterial separately with a pre-weighed mass of Bioroot powder. The microstructural properties and compressive strength of the different hardened composites obtained were investigated. The composites have been characterized by X-ray Diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Compression testing was performed.

RESULTS

The 1-wt.% composites, Bioroot/MWCNTs, and Bioroot/TC, except for the one reinforced with BN, displayed a significant improvement in the compressive strength compared to pristine BioRoot™ RCS. The 2-wt.% composites showed no significant improvement in the compressive strength.

CONCLUSION

The addition of 1-wt.% MWCNTs and TC nanomaterials can be considered in the future for enhancing the microstructure and compressive strength properties of pristine BioRoot™ RCS.

Mechanical Behavior of Bi-Layer and Dispersion Coatings Composed of Several Nanostructures on Ti13Nb13Zr Alloy

Titanium implants are commonly used because of several advantages, but their surface modification is necessary to enhance bioactivity. Recently, their surface coatings were developed to induce local antibacterial properties. The aim of this research was to investigate and compare mechanical properties of three coatings: multi-wall carbon nanotubes (MWCNTs), bi-layer composed of an inner MWCNTs layer and an outer TiO₂ layer, and dispersion coatings comprised of simultaneously deposited MWCNTs and nanoCu, each electrophoretically deposited on the Ti13Nb13Zr alloy. Optical microscopy, scanning electron microscopy, X-ray electron diffraction spectroscopy, and nanoindentation technique were applied to study topography, chemical composition, hardness, plastic and elastic properties. The results demonstrate that the addition of nanocopper or titanium dioxide to MWCNTs coating increases hardness, lowers Young’s modulus, improves plastic and elastic properties, wear resistance under deflection, and plastic deformation resistance. The results can be attributed to different properties, structure and geometry of applied particles, various deposition techniques, and the possible appearance of porous structures. These innovative coatings of simultaneously high strength and elasticity are promising to apply for deposition on long-term titanium implants.

Vancomycin-Loaded Collagen/Hydroxyapatite Layers Electrospun on 3D Printed Titanium Implants Prevent Bone Destruction Associated with S. epidermidis Infection and Enhance Osseointegration

The aim of the study was to develop an orthopedic implant coating in the form of vancomycin-loaded collagen/hydroxyapatite layers (COLHA+V) that combine the ability to prevent bone infection with the ability to promote enhanced osseointegration. The ability to prevent bone infection was investigated employing a rat model that simulated the clinically relevant implant-related introduction of bacterial contamination to the bone during a surgical procedure using a clinical isolate of Staphylococcus epidermidis. The ability to enhance osseointegration was investigated employing a model of a minipig with terminated growth. Six weeks following implantation, the infected rat femurs treated with the implants without vancomycin (COLHA+S. epidermidis) exhibited the obvious destruction of cortical bone as evinced via a cortical bone porosity of up to 20% greater than that of the infected rat femurs treated with the implants containing vancomycin (COLHA+V+S. epidermidis) (3%) and the non-infected rat femurs (COLHA+V) (2%). The alteration of the bone structure of the infected COLHA+S. epidermidis group was further demonstrated by a 3% decrease in the average Ca/P molar ratio of the bone mineral. Finally, the determination of the concentration of vancomycin released into the blood stream indicated a negligible systemic load. Six months following implantation in the pigs, the quantified ratio of new bone indicated an improvement in osseointegration, with a two-fold bone ingrowth on the COLHA (47%) and COLHA+V (52%) compared to the control implants without a COLHA layer (27%). Therefore, it can be concluded that COLHA+V layers are able to significantly prevent the destruction of bone structure related to bacterial infection with a minimal systemic load and, simultaneously, enhance the rate of osseointegration.

Adsorption characteristics of Pb(II), Cd(II) and Cu(II) on carbon nanotube-hydroxyapatite

Based on batch experiments, we investigate the adsorption characteristics of Pb(II), Cd(II) and Cu(II) on multi-walled carbon nanotube-hydroxyapatite (MWCNT-HAP) composites in detail and explore the effects of the solid-to-liquid ratio, pH, the ionic strength, reaction time and temperature on adsorption. The results show that the adsorption on MWCNT-HAP follows Pb(II)>Cu(II)>Cd(II). With an increasing solid-to-liquid ratio, the adsorption quantity of Pb(II), Cd(II) and Cu(II) on MWCNT-HAP decreases, whereas the removal efficiency increases. The optimal pH for adsorption is 4.0∼6.0. The effect of the ionic strength on the adsorption of Cd(II) is pronounced, whereas that on the adsorption of Pb(II) and Cu(II) is small. In the single-component system and ternary-component system, the adsorption processes for Pb(II), Cd(II) and Cu(II) on MWCNT-HAP have fast kinetics, and the pseudo-second-order kinetics model can well describe the adsorption kinetics of the three heavy metals. The adsorption of Pb(II), Cd(II) and Cu(II) on MWCNT-HAP is spontaneous and endothermic, and the Langmuir model can well simulate the isothermal adsorption of Pb(II) and Cu(II), whereas the Langmuir and Freundlich models can be used to describe the isothermal adsorption of Cd(II).

Synthesis and characterization of graphene oxide-zirconia (GO-ZrO2) and hydroxyapatite-zirconia (HA-ZrO2) nano-fillers for resin-based composites for load-bearing applications

OBJECTIVES

The study aims to synthesize two different types of nano-fillers based on zirconia (ZrO₂), which was functionalized with graphene oxide (GO-ZrO₂), and hydroxyapatite (HA-ZrO₂), and to implement them in an experimental methacrylate matrix containing new dimethacrylic oligomers.

METHODS

Nano-particles were synthesized via a modified Hummer's method and a sol-gel route. Bisphenol A-glycidyl methacrylate oligomers (Bis-GMA_336[0-1]) were synthesized from an epoxy resin that reacted with methacrylic acid in the presence of a basic catalyst. Traditional dental glass-fillers (Barium oxide/BaO and Barium fluoride/BaF₂) were synthesized to create an experimental resin-based composite (RBC) used as reference. Filler morphology was evaluated via Transmission Electron Microscopy. RBCs were characterised by real-time Fourier transform infrared spectroscopy (degree of cure/DC, polymerisation kinetics), real-time spectrometry (light transmittance), 3-point bending test (flexural strength and modulus, Weibull parameters), and depth-sensing indentation test (plastic and elastic deformation parameters).

RESULTS

The synthesized nanohybrid fillers proved good dispersing performance. Mechanical properties and materials' reliability are within or above the mean values reported in the literature for RBCs. Addition of HA-ZrO₂-fillers resulted in a decrease light transmission, DC and mechanical properties. Except for the HA-ZrO₂ RBC, materials showed a high resistance to softening in solvent.

CONCLUSIONS

The synthesis of GO-ZrO₂ and HA-ZrO₂ nanohybrid particles and their implementation in experimental RBCs has proven successful. Adjustments of the light transmission through suitable co-fillers in addition to GO-ZrO₂ as well as adjustments of the amount of HA-ZrO₂ are necessary to enable reduced curing time (<20 s).

CLINICAL SIGNIFICANCE

The addition of nanofillers with tailor-made properties can help improving the performance of modern restoratives.

Excellency of Hydroxyapatite Composite Scaffolds for Bone Tissue Engineering

The hydroxyapatite [HAp, Ca10(PO4)6(OH)2] has a variety of applications in bone fillers and replacements due to its excellent bioactivity and osteoconductivity. It comprises the main inorganic component of hard tissues. Among the various approaches, a composite approach using several components like biopolymer, gelatin, collagen, and chitosan in the functionalization of scaffolds with HAp has the prospective to be an engineered biomaterial for bone tissue engineering. HAp composite scaffolds have been developed to obtain a material with different functionalities such as surface reactivity, bioactivity, mechanical strength, and capability of drug or growth factor delivery. Several techniques and processes for the synthesis and fabrication of biocompatible HAp composite scaffolds suitable for bone regeneration are addressed here. Further, this chapter described the excellences of various HAp composite scaffolds used in in vitro and in vivo experiments in bone tissue engineering.

Customized Therapeutic Surface Coatings for Dental Implants

Dental implants are frequently used to support fixed or removable dental prostheses to replace missing teeth. The clinical success of titanium dental implants is owed to the exceptional biocompatibility and osseointegration with the bone. Therefore, the enhanced therapeutic effectiveness of dental implants had always been preferred. Several concepts for implant coating and local drug delivery had been developed during the last decades. A drug is generally released by diffusion-controlled, solvent-controlled, and chemical controlled methods. Although a range of surface modifications and coatings (antimicrobial, bioactive, therapeutic drugs) have been explored for dental implants, it is still a long way from designing sophisticated therapeutic implant surfaces to achieve the specific needs of dental patients. The present article reviews various interdisciplinary aspects of surface coatings on dental implants from the perspectives of biomaterials, coatings, drug release, and related therapeutic effects. Additionally, the various types of implant coatings, localized drug release from coatings, and how released agents influence the bone–implant surface interface characteristics are discussed. This paper also highlights several strategies for local drug delivery and their limitations in dental implant coatings as some of these concepts are yet to be applied in clinical settings due to the specific requirements of individual patients.

Bone Tissue Engineering via Carbon-Based Nanomaterials

Bone tissue engineering (BTE) has received significant attention due to its enormous potential in treating critical-sized bone defects and related diseases. Traditional materials such as metals, ceramics, and polymers have been widely applied as BTE scaffolds; however, their clinical applications have been rather limited due to various considerations. Recently, carbon-based nanomaterials attract significant interests for their applications as BTE scaffolds due to their superior properties, including excellent mechanical strength, large surface area, tunable surface functionalities, high biocompatibility as well as abundant and inexpensive nature. In this article, recent studies and advancements on the use of carbon-based nanomaterials with different dimensions such as graphene and its derivatives, carbon nanotubes, and carbon dots, for BTE are reviewed. Current challenges of carbon-based nanomaterials for BTE and future trends in BTE scaffolds development are also highlighted and discussed.

Functionally graded titanium implants: Characteristic enhancement induced by combined severe plastic deformation

Commercially pure titanium was processed by equal channel angular pressing (ECAP) and surface mechanical attrition treatment (SMAT) for the purpose of developing functionally graded titanium used for implants and a gradient structure including nanostructured, deformed and undeformed zones were produced on the samples. In particular, it was aimed to design the gradient-structure in the titanium with enhanced properties by applying 4 ECAP passes to form bulk structure of ultrafine-grains and subsequently subjecting SMAT to the surface of ECAPed samples to produce nanostructured surface region. Microstructural examination was made by electron back scatter diffraction (EBSD). Also, microhardness, nanoindentation, topography, roughness and wettability were evaluated. To examine the biological response, human osteosarcoma cells were cultured in contact with the samples in various time periods and morphology change, cell viability and alkaline phosphate activity were conducted also cell morphology was monitored. EBSD showed development of ultrafine-grained structure after 4 passes of ECAP with an average grain size of 500 nm. Applying SMAT resulted in additional refinement in the ECAP samples, particularly in the subsurface regions to a depth of 112 μm. Furthermore, the SMATed samples showed an enhancement in roughness, wettability and hardness magnitudes. Viability enhanced up to 7% in SMATed + ECAPed sample, although the acceptable cell adhesion, improved cell differentiation and mineralization were seen. The combined use of ECAP and SMAT has shown a good potential for optimizing the design of modern functionally graded medical devices and implants.

Biocomposites based on hydroxyapatite matrix reinforced with nanostructured monticellite (CaMgSiO4) for biomedical application: Synthesis, characterization, and biological studies

In this study, a simple and facile strategy was developed for the synthesis of novel hydroxyapatite (HA)/nanostructured monticellite ceramic composites by mechanical method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) were used to peruse the phase structure, and morphology of soaked ceramic composites in simulated body fluid (SBF). The in vitro bioactivity of HA-based ceramic composites with nanostructured monticellite ranging from 0 to 50 wt% was evaluated via investigating the formation ability of bone-like calcium phosphates in SBF and the effect of obtained extracts from composites dissolution on osteoblast-like G-292 cell line. Moreover, In vitro cytocompatibility of the HA/monticellite ceramic composites was investigated by MTT, cell growth & adhesion and alkaline phosphatase (ALP) activity assays, and quantitative real-time PCR analysis. The results showed that HA/nanostructured monticellite ceramic composites could induce apatite formation in SBF. The cell proliferation and growth exposed to ceramic composites extracts were significantly stimulated and promoted at a certain concentration range compared to control for various time periods of cell culture. The optimized composite extract enhanced considerably gene expression of G-292 type X collagen (COLX) at different days. Also, G-292 cells were spread and adhered well on the ceramic composite disc. Furthermore, ALP activity of G-292 cells exposed to ceramic composites extracts was dramatically enhanced in comparison with pure HA extract (as control) at different concentrations for various time periods of cell culture. The results suggest that the optimized HA/nanostructured monticellite composite is promising biomaterial for clinical applications such as orthopedic and dentistry.

Biocompatibility Characteristics of Titanium Coated with Multi Walled Carbon Nanotubes-Hydroxyapatite Nanocomposites

Multi walled carbon nanotubes-hydroxyapatite (MWCNTs-HA) with various contents of MWCNTs was synthesized using the sol-gel method. MWCNTs-HA composites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). HA particles were generated on the surface of MWCNT. Produced MWCNTs-HA nanocomposites were coated on pure titanium (PT). Characteristic of the titanium coated MWCNTs-HA was evaluated by field-emission scanning electron microscopy (FE-SEM) and XRD. The results show that the titanium surface was covered with MWCNTs-HA nanoparticles and MWCNTs help form the crystalized hydroxyapatite. Furthermore, the MWCNTs-HA coated titanium was investigated for in vitro cellular responses. Cell proliferation and differentiation were improved on the surface of MWCNT-HA coated titanium.

Multiwalled Carbon Nanotubes for Dental Applications

Multiwalled carbon nanotubes (MWCNTs) are a particularly promising drug delivery system due to their high surface area allowing high-protein loading, their stability under biological conditions, and their unique interaction with cellular membranes. Studies have shown that covalent attachment of polyethylene glycol (PEG) improves biocompatibility and enhances surface hydrophilicity properties, suggesting that PEGylated MWCNTs are efficient and toxic-safe drug delivery systems. So far, CNTs are used for a broad range of applications in dentistry, especially for dental tissue repair and restorative. Here we present a protocol of protein immobilization onto MWCNTs and describe the procedure for delivering them into the cells after characterization of the nanotubes.

Research Progress Regarding Interfacial Characteristics and the Strengthening Mechanisms of Titanium Alloy/Hydroxyapatite Composites

Titanium alloy/Hydroxyapatite (HA) composites have become a hot research topic in biomedical materials, while there are some challenges concerning bioactivity and mechanical properties such as low interface adhesion at the interface between metal and ceramic, complex interfacial reactions, and so on. Nevertheless, composites with reinforced phases can reach special properties that meet the requirements of biomedical materials due to the strong interfacial interactions between reinforcing phases (nano-carbon, partial oxides, and so on) and Titanium alloys or HA. This review summarizes the interface properties and mechanisms of Titanium alloy/HA composites, including interfacial bonding methods, strengthening and toughening mechanisms, and performance evaluation. On this basis, the interface characteristics and mechanisms of the Titaniumalloy/HA composites with enhanced phase are prospected. The results show that the interfacial bonding methods in the Titanium alloy/HA composites include chemical reactions and mechanical effects. The strengthening and toughening mechanisms contain grain refinement strengthening, second phase strengthening, solution strengthening, cracks and pulling out mechanisms, etc. This review provides a guidline for the fabrication of biocomposites with both mechanical properties and bioactivity.

Carbon nanotube, graphene and boron nitride nanotube reinforced bioactive ceramics for bone repair

The high brittleness and low strength of bioactive ceramics have severely restricted their application in bone repair despite the fact that they have been regarded as one of the most promising biomaterials. In the last few years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have gained increasing attention owing to their favorable biocompatibility, large surface specific area and super mechanical properties. These qualities make LDNs potential nanofillers in reinforcing bioactive ceramics. In this review, the types, characteristics and applications of the commonly used LDNs in ceramic composites are summarized. In addition, the fabrication methods for LDNs/ceramic composites, such as hot pressing, spark plasma sintering and selective laser sintering, are systematically reviewed and compared. Emphases are placed on how to obtain the uniform dispersion of LDNs in a ceramic matrix and maintain the structural stability of LDNs during the high-temperature fabrication process of ceramics. The reinforcing mechanisms of LDNs in ceramic composites are then discussed in-depth. The in vitro and in vivo studies of LDNs/ceramic in bone repair are also summarized and discussed. Finally, new developments and potential applications of LDNs/ceramic composites are further discussed with reference to experimental and theoretical studies.

STATEMENT OF SIGNIFICANCE

Despite bioactive ceramics having been regarded as promising biomaterials, their high brittleness and low strength severely restrict their application in bone scaffolds. In recent years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have shown great potential in reinforcing bioactive ceramics owing to their unique structures and properties. However, so far it has been difficult to maintain the structural stability of LDNs during fabrication of LDNs/ceramic composites, due to the lengthy, high-temperature process involved. This review presents a comprehensive overview of the developments and applications of LDNs in bioactive ceramics. The newly-developed fabrication methods for LDNs/ceramic composites, the reinforcing mechanisms and the in vitro and in vivo performance of LDNs are also summarized and discussed in detail.

Corrosion resistance and bioactivity enhancement of MAO coated Mg alloy depending on the time of hydrothermal treatment in Ca-EDTA solution

In this study, a two-step surface treatment was developed to restrain the rapid primary degradation of a biodegradable Mg alloy and to improve their biocompatibility. Micro arc oxidation (MAO) coating was performed in alkaline electrolytes such as 1.0 M NaOH with 0.1 M glycerol and 0.1 M Na3PO4. Hydrothermal treatment was performed in 0.1 M Ca-EDTA (C10H12CaN2Na2O8) and 0.5 M NaOH solution at 90 °C for different times (6, 12, 24, and 48 h). The film morphology and chemical properties were evaluated by XRD and FE-SEM. The electrochemical and corrosion behaviors were examined in the simulated body fluid, and cytotoxicity was assessed using MC3T3-E1 cells. After MAO coating, an oxide layer containing [Formula: see text] formed on the surface. During the hydrothermal treatment in Ca-EDTA solution, calcium phosphate and Mg(OH)2 were produced via a reaction between [Formula: see text] on the surface and Ca2+ in solution. The layer with ceramics and oxides was grown on the surface with increasing hydrothermal treatment time, and improved the surface corrosion resistance. The 24 h hydrothermal-treated group showed the lowest immersion corrosion rate and high cell viability. Therefore, this treatment was the most favorable surface modification for improving the initial corrosion resistance and bioactivity of the biodegradable Mg alloy.

The innovative applications of therapeutic nanostructures in dentistry

Nanotechnology has paved multiple ways in preventing, reversing or restoring dental caries which is one of the major health care problems. Nanotechnology aided in processing variety of nanomaterials with innovative dental applications. Some showed antimicrobial effect helping in the preventive stage. Others have remineralizing potential intercepting early lesion progression as nanosized calcium phosphate, carbonate hydroxyapatite nanocrystals, nanoamorphous calcium phosphate and nanoparticulate bioactive glass particularly with provision of self-assembles protein that furnish essential role in biomimetic repair. The unique size of nanomaterials makes them fascinating carriers for dental products. Thus, it is recentlyclaimedthat fortifying the adhesives with nanomaterials that possess biological meritsdoes not only enhance the mechanical and physical properties of the adhesives, but also help to attain and maintain a durable adhesive joint and enhanced longevity. Accordingly, this review will focus on the current status and the future implications of nanotechnology in preventive and adhesive dentistry.

Hydroxyapatite–-Past, Present, and Future in Bone Regeneration

Hydroxyapatite (HA) is an essential element required for bone regeneration. Different forms of HA have been used for a long time. The essence of bone regeneration always revolves around the healthy underlying bone or it may be the surroundings that give enough strength. HA is well known for bone regeneration through conduction or by acting as a scaffold for filling of defects from ancient times, but emerging trends of osteoinductive property of HA are much promising for new bone regeneration. Emerging technology has made the dreams of clinicians to realize the use of HA in different forms for various regenerative purposes both in vivo and in vitro. The nanostructured calcium apatite plays an important role in the construction of calcified tissues. The nanostructured material has the ability to attach biological molecules such as proteins, which can be used as functional materials in many aspects, and the capability of synthesizing controlled structures of apatite to simulate the basic structure of bone and other calcified tissues. The process of regeneration requires a biomimetic and biocompatible nanostructured novel material. The nanostructured bioceramic particles are of interest in synthetic bone grafts and bone cements both injectable and controlled setting, so that such composites will reinforce the strength of bioceramics. Extensive research is being carried out for bone regeneration using nanotechnology. Artificial bone formation is not far from now. Nanotechnology has made many dreams come true. This paper gives comprehensive insights into the history and evolution with changing trends in the use of HA for various regenerative purposes.

Structure, apatite inducing ability, and corrosion behavior of chitosan/halloysite nanotube coatings prepared by electrophoretic deposition on titanium substrate

In this study chitosan/halloysite nanotube composite (CS/HNT) coatings were deposited by electrophoretic deposition (EPD) on titanium substrate. Using HNT particles were investigated as new substituents for carbon nanotubes (CNTs) in chitosan matrix coatings. The ability of chitosan as a stabilizing, charging, and blending agent for HNT particles was exploited. Furthermore, the effects of pH, electrophoretic bath, and sonicating duration were studied on the deposition of suspensions containing HNT particles. Microstructure properties of coatings showed uniform distribution of HNT particles in chitosan matrix to form smooth nanocomposite coatings. The zeta potential results revealed that at pH around 3 there is an isoelectric point for HNT and it would have cathodic and anionic states at pH values less and more than 3, respectively. Therefore, CS/HNT composite deposits were produced in the pH range of 2.5 to 3. The apatite inducing ability of chitosan-HNT composite coating assigned that HNT particles were biocompatible because they formed carbonated hydroxyapatite particles on CS/HNT coating in corrected simulated body fluid (C-SBF). Finally, electrochemical corrosion characterizations determined that corrosion resistance in CS/HNT coating has been improved compared to bare titanium substrate.

Effect of the addition CNTs on performance of CaP/chitosan/coating deposited on magnesium alloy by electrophoretic deposition

CaP/chitosan/carbon nanotubes (CNTs) coating on AZ91D magnesium alloy was prepared via electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). The bonding between the layer and the substrate was studied by an automatic scratch instrument. The phase compositions and microstructures of the composite coatings were determined by using X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscope (SEM). The element concentration and gentamicin concentration were respectively determined by inductively coupled plasma optical emission spectrometer (ICP-OES) test and ultraviolet spectrophotometer (UV). The cell counting kit (CCK) assay was used to evaluate the cytotoxicity of samples to SaOS-2 cells. The results showed that a few CNTs with their original tubular morphology could be found in the CaP/chitosan coating and they were beneficial for the crystal growth of phosphate and improvement of the coating bonding when the addition amount of CNTs in 500 ml of electrophoretic solution was from 0.05 g to 0.125 g. The loading amount of gentamicin increased and the releasing speed of gentamicin decreased after CNTs was added into the CaP/chitosan coating for immersion loading and EPD loading. The cell viability of Mg based CaP/chitosan/CNTs was higher than that of Mg based CaP/chitosan from 16 days to 90 days.

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 µm thick yttrium iron garnet films that are  > 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

Since various interactions among cells, surrounding tissues and implanted biomaterials always occur at their interfaces, the surface properties of potential implants appear to be of paramount importance for the clinical success. In view of the fact that a limited amount of materials appear to be tolerated by living organisms, a special discipline called surface engineering was developed to initiate the desirable changes to the exterior properties of various materials but still maintaining their useful bulk performances. In 1975, this approach resulted in the introduction of a special class of artificial bone grafts, composed of various mechanically stable (consequently, suitable for load bearing applications) implantable biomaterials and/or bio-devices covered by calcium orthophosphates (CaPO4) to both improve biocompatibility and provide an adequate bonding to the adjacent bones. Over 5000 publications on this topic were published since then. Therefore, a thorough analysis of the available literature has been performed and about 50 (this number is doubled, if all possible modifications are counted) deposition techniques of CaPO4 have been revealed, systematized and described. These CaPO4 deposits (coatings, films and layers) used to improve the surface properties of various types of artificial implants are the topic of this review.

Advances in Nanotechnology for Restorative Dentistry

Rationalizing has become a new trend in the world of science and technology. Nanotechnology has ascended to become one of the most favorable technologies, and one which will change the application of materials in different fields. The quality of dental biomaterials has been improved by the emergence of nanotechnology. This technology manufactures materials with much better properties or by improving the properties of existing materials. The science of nanotechnology has become the most popular area of research, currently covering a broad range of applications in dentistry. This review describes the basic concept of nanomaterials, recent innovations in nanomaterials and their applications in restorative dentistry. Advances in nanotechnologies are paving the future of dentistry, and there are a plenty of hopes placed on nanomaterials in terms of improving the health care of dental patients.

Bioactivity behaviour of nano-hydroxyapatite/freestanding aligned carbon nanotube oxide composite

Bioactive and low cytotoxic three dimensional nano-hydroxyapatite (nHAp) and aligned carbon nanotube oxide (a-CNTO) composite has been investigated. First, freestanding aligned carbon nanotubes porous scaffold was prepared by large-scale thermal chemical vapour deposition and functionalized by oxygen plasma treatment, forming a-CNTO. The a-CNTO was covered with plate-like nHAp crystals prepared by in situ electrodeposition techniques, forming nHAp/a-CNTO composite. After that nHAp/a-CNTO composite was immersed in simulated body fluid for composite consolidation. This novel nanobiomaterial promotes mesenchymal stem cell adhesion with the active formation of membrane projections, cell monolayer formation and high cell viability.

Synthesis and bioactivity of gelatin/multiwalled carbon nanotubes/hydroxyapatite nanofibrous scaffolds towards bone tissue engineering

The in vitro bioactivity of scaffolds, and the adhesion, mineralization, viability and proliferation of hFOBs on gelatin/MWNTs/HA nanofibrous scaffolds.

Single walled carbon nanotubes reinforced mineralized hydroxyapatite composite coatings on titanium for improved biocompatible implant applications

Carbon nanotubes reinforced mineralized hydroxyapatite (CNT/M-HAP) composite coating on titanium by pulsed electrodeposition is a promising approach to produce bioimplants with better osseointegration capacity and improved mechanical property.

Novel bioactive antimicrobial lignin containing coatings on titanium obtained by electrophoretic deposition

Hydroxyapatite (HAP) is the most suitable biocompatible material for bone implant coatings; its brittleness, however, is a major obstacle, and the reason why research focuses on creating composites with biopolymers. Organosolv lignin (Lig) is used for the production of composite coatings, and these composites were examined in this study. Titanium substrate is a key biomedical material due to its well-known properties, but infections of the implantation site still impose a serious threat. One approach to prevent infection is to improve antimicrobial properties of the coating material. Silver doped hydroxyapatite (Ag/HAP) and HAP coatings on titanium were obtained by an electrophoretic deposition method in order to control deposited coating mass and morphology by varying applied voltage and deposition time. The effect of lignin on microstructure, morphology and thermal behavior of biocomposite coatings was investigated. The results showed that higher lignin concentrations protect the HAP lattice during sintering, improving coating stability. The corrosion stability was evaluated in simulated body fluid (SBF) at 37 °C. Newly formed plate-shaped carbonate-HAP was detected, indicating enhanced bioactive performance. The antimicrobial efficiency of Ag/HAP/Lig was confirmed by its higher reduction of bacteria Staphylococcus aureus TL (S. aureus TL) than of HAP/Lig coating. Cytotoxicity assay revealed that both coatings can be classified as non-toxic against healthy immunocompetent peripheral blood mononuclear cells (PBMC).

Hydroxyapatite and silk combination-coated dental implants result in superior bone formation in the peri-implant area compared with hydroxyapatite and collagen combination-coated implants

PURPOSE

The objective of this study was to compare bone formation after installation of uncoated (UC), hydroxyapatite-coated (HA), collagen plus HA-coated (CH), and silk plus HA-coated (SH) implants.

MATERIALS AND METHODS

Implants in the UC group had acid-etched surfaces. Surface coating was applied using the aerosol deposition method. Cellular responses on the coated surfaces were examined with scanning electron microscopy. Cellular responses to the surfaces were studied with the corresponding coated discs and MG63 cells. Subsequently, 3-(4, 5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphatase (ALP) assays were performed. Peri-implant bone formation was evaluated with the rabbit tibia model. Twenty-four implants from each group were installed. The animals were sacrificed 6 weeks after implant installation. Peri-implant bone formation and implant-to-bone contact were measured in histologic sections. Significance of differences across groups was evaluated using analysis of variance.

RESULTS

Scanning electron microscopic images showed that the CH and SH groups exhibited cells that appeared more spread out than those in the other groups. The SH group exhibited the highest value in the MTT assay. The CH group exhibited the highest level of ALP activity. Comparisons of these modifications with the acid-etched surfaces showed that the CH and SH groups displayed significantly greater peri-implant bone formation (P < .001).

CONCLUSION

The SH group displayed significantly greater new bone formation and bone-to-implant contact than did the other groups.

Electrophoretic Deposition of Carbon Nanotubes over TiO2 Nanotubes: Evaluation of Surface Properties and Biocompatibility

Titanium (Ti) is often used as an orthopedic and dental implant material due to its better mechanical properties, corrosion resistance, and excellent biocompatibility. Formation of TiO2 nanotubes (TiO2 NTs) on titanium is an interesting surface modification to achieve controlled drug delivery and to promote cell growth. Carbon nanotubes (CNTs) possess excellent chemical durability and mechanical strength. The use of CNTs in biomedical applications such as scaffolds has received considerable attention in recent years. The present study aims to modify the surface of titanium by anodizing to form TiO2 NTs and subsequently deposit CNTs over it by electrophoretic deposition (EPD). Characteristic, biocompatibility, and apatite forming ability of the surface modified samples were evaluated. The results of the study reveal that CNTs coating on TiO2 nanotubes help improve the biological activity and this type of surface modification is highly suitable for biomedical applications.

Bioinspired nanoscale materials for biomedical and energy applications

The demand for green, affordable and environmentally sustainable materials has encouraged scientists in different fields to draw inspiration from nature in developing materials with unique properties such as miniaturization, hierarchical organization and adaptability. Together with the exceptional properties of nanomaterials, over the past century, the field of bioinspired nanomaterials has taken huge leaps. While on the one hand, the sophistication of hierarchical structures endows biological systems with multi-functionality, the synthetic control on the creation of nanomaterials enables the design of materials with specific functionalities. The aim of this review is to provide a comprehensive, up-to-date overview of the field of bioinspired nanomaterials, which we have broadly categorized into biotemplates and biomimics. We discuss the application of bioinspired nanomaterials as biotemplates in catalysis, nanomedicine, immunoassays and in energy, drawing attention to novel materials such as protein cages. Furthermore, the applications of bioinspired materials in tissue engineering and biomineralization are also discussed.

Processing strategies for smart electroconductive carbon nanotube-based bioceramic bone grafts

Electroconductive bone grafts have been designed to control bone regeneration. Contrary to polymeric matrices, the translation of the carbon nanotube (CNT) electroconductivity into oxide ceramics is challenging due to the CNT oxidation during sintering. Sintering strategies involving reactive-bed pressureless sintering (RB + P) and hot-pressing (HP) were optimized towards prevention of CNT oxidation in glass/hydroxyapatite (HA) matrices. Both showed CNT retentions up to 80%, even at 1300 °C, yielding an increase of the electroconductivity in ten orders of magnitude relative to the matrix. The RB + P CNT compacts showed higher electroconductivity by ∼170% than the HP ones due to the lower damage to CNTs of the former route. Even so, highly reproducible conductivities with statistical variation below 5% and dense compacts up to 96% were only obtained by HP. The hot-pressed CNT compacts possessed no acute toxicity in a human osteoblastic cell line. A normal cellular adhesion and a marked orientation of the cell growth were observed over the CNT composites, with a proliferation/differentiation relationship favouring osteoblastic functional activity. These sintering strategies offer new insights into the sintering of electroconductive CNT containing bioactive ceramics with unlimited geometries for electrotherapy of the bone tissue.

Hydroxyapatite and collagen combination-coated dental implants display better bone formation in the peri-implant area than the same combination plus bone morphogenetic protein-2-coated implants, hydroxyapatite only coated implants, and uncoated implants

PURPOSE

The objective of this study was to compare peri-implant bone formation among uncoated (UC), hydroxyapatite (HA), collagen plus HA (CH), and collagen, HA, plus bone morphogenetic protein-2 (BMP-2) implant groups.

MATERIALS AND METHODS

Implants in the UC group had acid-etched surfaces. The surface coating was applied using the aerosol deposition method. The coated surfaces were examined by scanning electron microscopy, x-ray diffraction (XRD), and Fourier-transformed infrared absorption analysis. Subsequently, 6 implants from each group (total, 24 implants) were installed in the tibias of rabbits. The animals were sacrificed at 6 weeks after implant installation. Peri-implant bone formation and bone-to-implant contact (BIC) were measured in histologic sections. Significant differences among groups were evaluated using analysis of variance.

RESULTS

Based on the measured XRD patterns, there was a characteristic HA phase (International Centre for Diffraction Data [ICDD], 086-0740) coated on the titanium (ICDD, 089-3725). Subsequent coating processes for collagen and BMP-2 did not display additional diffraction peaks, but maintained the diffraction patterns of the HA-coated titanium. The presence of collagen was verified by infrared absorption analysis. When comparing these modifications with UC surfaces, only the CH coating displayed significantly greater peri-implant bone formation and BIC (P = .003 and P < .001, respectively). Adding BMP-2 to the implant surface did not produce any advantage compared with the CH coating.

CONCLUSIONS

In this study, the CH group displayed significantly greater new bone formation and BIC than the other groups. There was no significant difference among the other groups.