Silver deposition on titanium surface by electrochemical anodizing process reduces bacterial adhesion of Streptococcus sanguinis and Lactobacillus salivarius

Silver-Doped Titanium Oxide Layers for Improved Photocatalytic Activity and Antibacterial Properties of Titanium Implants

Titanium has a long history of clinical use, but the naturally forming oxide is not ideal for bacterial resistance. Anodization processes can modify the crystallinity, surface topography, and surface chemistry of titanium oxides. Anatase, rutile, and mixed phase oxides are known to exhibit photocatalytic activity (PCA)-driven bacterial resistance under UVA irradiation. Silver additions are reported to enhance PCA and reduce bacterial attachment. This study investigated the effects of silver-doping additions to three established anodization processes. Silver doping showed no significant influence on oxide crystallinity, surface topography, or surface wettability. Oxides from a sulfuric acid anodization process exhibited significantly enhanced PCA after silver doping, but silver-doped oxides produced from phosphoric-acid-containing electrolytes did not. Staphylococcus aureus attachment was also assessed under dark and UVA-irradiated conditions on each oxide. Each oxide exhibited a photocatalytic antimicrobial effect as indicated by significantly decreased bacterial attachment under UVA irradiation compared to dark conditions. However, only the phosphorus-doped mixed anatase and rutile phase oxide exhibited an additional significant reduction in bacteria attachment under UVA irradiation as a result of silver doping. The antimicrobial success of this oxide was attributed to the combination of the mixed phase oxide and higher silver-doping uptake levels.

Silver coating on dental implant-abutment connection screws as potential strategy to prevent loosening and minimizing bacteria adhesion

Introduction: One of the main problems for the long-term behavior of dental implants are loosening of the implant-abutment connection screws and bacterial infiltration. The aim of this work is to increase the screw fixation by silver coating, providing superior mechanical retaining and antibacterial effect. Methods: Eighty dental implants with their abutments and screws have been studied. Twenty screws were not coated and were used as a control while the rest of screws were silver coated by sputtering, with three different thickness: 10, 20 and 40 μm and 20 screws per each thickness. Coating morphology and thickness were determined by scanning electron microscopy using image analysis systems. The screws were tightened for each of the thicknesses and the control with two torques 15 Ncm and 20 Ncm and tested under mechanical fatigue simulating oral stresses up to a maximum of 500,000 cycles. The remaining torques at different cycles were determined with a high-sensitivity torquemeter. Cell viability assays were performed with SaOs-2 osteoblasts and microbiological studies were performed against Streptococcus gordonii and Enterococcus faecalis bacteria strains, determining their metabolic activity and viability using live/dead staining. Results: It was observed a decrease in torque as cycles increase. For a preload of 15 Ncm at 100,000 cycles, the loosening was complete and, for 20 Ncm at 500,000 cycles, 85% of torque was lost. The silver coatings retained the torque, especially the one with a thickness of 40 μm, retaining 90% of the initial torque at 500,000 cycles. It was observed that osteoblastic viability values did not reach 70%, which could indicate a slight cytotoxic effect in contact with cells or tissues; however, the screw should not be in direct contact with tissue or living cells. Silver coating induced a significant reduction of the bacteria metabolic activity for Streptococcus gordonii and Enterococcus faecalis, around 90% and 85% respectively. Discussion: Therefore, this coating may be of interest to prevent loosening of implant systems with a worthy antibacterial response.

Nanotechnology for Dentistry: Prospects and Applications

In the XXI century, application of nanostructures in oral medicine has become common. In oral medicine, using nanostructures for the treatment of dental caries constitutes a great challenge. There are extensive studies on the implementation of nanomaterials to dental composites in order to improve their properties, e.g., their adhesive strength. Moreover, nanostructures are helpful in dental implant applications as well as in maxillofacial surgery for accelerated healing, promoting osseointegration, and others. Dental personal care products are an important part of oral medicine where nanomaterials are increasingly used, e.g., toothpaste for hypersensitivity. Nowadays, nanoparticles such as macrocycles are used in different formulations for early cancer diagnosis in the oral area. Cancer of the oral cavity-human squamous carcinoma-is the sixth leading cause of death. Detection in the early stage offers the best chance at total cure. Along with diagnosis, macrocycles are used for photodynamic mechanism-based treatments, which possess many advantages, such as protecting healthy tissues and producing good cosmetic results. Application of nanostructures in medicine carries potential risks, like long-term influence of toxicity on body, which need to be studied further. The introduction and development of nanotechnologies and nanomaterials are no longer part of a hypothetical future, but an increasingly important element of today's medicine.

Comparison of the Antibacterial Effect of Silver Nanoparticles and a Multifunctional Antimicrobial Peptide on Titanium Surface

Titanium implantation success may be compromised by Staphylococcus aureus surface colonization and posterior infection. To avoid this issue, different strategies have been investigated to promote an antibacterial character to titanium. In this work, two antibacterial agents (silver nanoparticles and a multifunctional antimicrobial peptide) were used to coat titanium surfaces. The modulation of the nanoparticle (≈32.1 ± 9.4 nm) density on titanium could be optimized, and a sequential functionalization with both agents was achieved through a two-step functionalization method by means of surface silanization. The antibacterial character of the coating agents was assessed individually as well as combined. The results have shown that a reduction in bacteria after 4 h of incubation can be achieved on all the coated surfaces. After 24 h of incubation, however, the individual antimicrobial peptide coating was more effective than the silver nanoparticles or their combination against Staphylococcus aureus. All tested coatings were non-cytotoxic for eukaryotic cells.

Effects of silver nanoparticle-based antimicrobial formulations on the properties of denture polymer: A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

Denture stomatitis and other oral infections are prevalent in denture wearers and can be treated effectively with an antimicrobial agent such as a silver nanoparticle-based polymer. However, the physical properties of the denture should not be adversely affected by the addition.

PURPOSE

The purpose of this systematic review and meta-analysis of in vitro studies was to analyze the effects of a silver nanoparticle-based antimicrobial resin on the properties of polymethyl methacrylate(PMMA)-based denture resin.

MATERIAL AND METHODS

Full-length English language articles reporting silver nanoparticle-based PMMA resin were included in the review, with no limitation on the year till May 2020. Scopus, Web of Sciences, and PubMed databases were accessed for the literature survey. The review was formulated based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and used the Consolidated Standards of Reporting Trials (CONSORT) guidelines and risk of bias Cochrane tool for quality assessment. A meta-analysis of flexural strength was performed by using a random-effects model at a 95% confidence interval. The other properties were analyzed descriptively.

RESULTS

Silver nanoparticle reinforcement caused considerable differences in the inherent physical material properties of PMMA.

CONCLUSIONS

An antimicrobial polymer nanocomposite formulation can either negatively affect or bring no improvement to the physical properties of denture resin.

The Potential of Surface-Immobilized Antimicrobial Peptides for the Enhancement of Orthopaedic Medical Devices: A Review

Due to the well-known phenomenon of antibiotic resistance, there is a constant need for antibiotics with novel mechanisms and different targets respect to those currently in use. In this regard, the antimicrobial peptides (AMPs) seem very promising by virtue of their bactericidal action, based on membrane permeabilization of susceptible microbes. Thanks to this feature, AMPs have a broad activity spectrum, including antibiotic-resistant strains, and microbial biofilms. Additionally, several AMPs display properties that can help tissue regeneration. A possible interesting field of application for AMPs is the development of antimicrobial coatings for implantable medical devices (e.g., orthopaedic prostheses) to prevent device-related infection. In this review, we will take note of the state of the art of AMP-based coatings for orthopaedic prostheses. We will review the most recent studies by focusing on covalently linked AMPs to titanium, their antimicrobial efficacy and plausible mode of action, and cytocompatibility. We will try to extrapolate some general rules for structure-activity (orientation, density) relationships, in order to identify the most suitable physical and chemical features of peptide candidates, and to optimize the coupling strategies to obtain antimicrobial surfaces with improved biological performance.

Bacteriostatic Poly Ethylene Glycol Plasma Coatings for Orthodontic Titanium Mini-Implants

Titanium mini-implants are used as anchorage for orthodontic tooth movements. However, these implants present problems due to the infection of surrounding tissues. The aim of this work was to obtain a polyethylene glycol (PEG) layer by plasma in order to achieve a bacteriostatic surface. Titanium surfaces were activated by argon plasma and, after, by PEG plasma with different powers (100, 150 and 200 W) for 30 and 60 min. The roughness was determined by white light interferometer microscopy and the wettability was determined by the contact angle technique. Surface chemical compositions were characterized by X-ray photoelectron spectroscopy (XPS) and cytocompatibility and cell adhesion studies were performed with fibroblast (hFFs) and osteoblast (SAOS-2) cells. Bacterial cultures with Spectrococcus Sanguinis and Lactobacillus Salivarius were performed, and bacterial colonization was determined. The results showed that plasma treatments do not affect the roughness. Plasma makes the surfaces more hydrophilic by decreasing the contact angles from 64.2° for titanium to 5.2° for argon-activated titanium, with values ranging from 12° to 25° for the different PEG treatments. The plasma has two effects: the cleaning of the surface and the formation of the PEG layer. The biocompatibility results were, for all cases, higher than 80%. The polymerization treatment with PEG reduced the adhesion of hFFs from 7000 to 6000 and, for SAOS-2, from 14,000 to 6500, for pure titanium and those treated with PEG, respectively. Bacterial adhesion was also reduced from 600 to 300 CFU/mm² for Spetrococcuns Sanguinis and from 10,000 to 900 CFU/mm² for Lactobacillus Salivarius. The best bacteriostatic treatment corresponded to PEG at 100 W and 30 s. As a consequence, the PEG coating would significantly prevent the formation of bacterial biofilm on the surface of titanium mini-implants.

Antimicrobial potential and osteoblastic cell growth on electrochemically modified titanium surfaces with nanotubes and selenium or silver incorporation

Titanium nanotube surfaces containing silver, zinc, and copper have shown antimicrobial effects without decreasing osteoblastic cell growth. In this in-vitro study we present first results on the biological evaluation of surface modifications by incorporating selenium and silver compounds into titanium-dioxide (TiO₂) nanotubes by electrochemical deposition. TiO₂-nanotubes (TNT) and Phosphate-doped TNT (pTNT) were grown on the surface of Ti6Al4V discs by anodization. Hydroxyapatite (HA), selenium (Se) and silver (Ag) compounds were incorporated by electrochemical deposition. Colony forming units of Staphylococcus epidermidis (DSM 3269) were significantly decreased in SepTNT (0.97 ± 0.18 × 10⁶ CFU/mL), SepTNT-HA (1.2 ± 0.39 × 10⁶ CFU/mL), AgpTNT (1.36 ± 0.42 × 10⁶ CFU/mL) and Ag₂SepTNT (0.999 ± 0.12 × 10⁶ CFU/mL) compared to the non-modified control (2.2 ± 0.21 × 10⁶ CFU/mL). Bacterial adhesion was calculated by measuring the covered area after fluorescence staining. Adhesion was lower in SepTNT (37.93 ± 12%; P = 0.004), pTNT (47.3 ± 6.3%, P = 0.04), AgpTNT (24.9 ± 1.8%; P < 0.001) and Ag₂SepTNT (14.9 ± 4.9%; P < 0.001) compared to the non-modified control (73.7 ± 11%). Biofilm formation and the growth of osteoblastic cells (MG-63) was observed by using Crystal Violet staining. Biofilm formation was reduced in SepTNT (22 ± 3%, P = 0.02) and Ag₂SepTNT discs (23 ± 11%, P = 0.02) compared to the non-modified control (54 ± 8%). In comparison with the non-modified control the modified SepTNT-HA and pTNT surfaces showed a significant higher covered area with osteoblastic MG-63-cells. Scanning electron microscope (SEM) images confirmed findings regarding bacterial and osteoblastic cell growth. These findings show a potential synergistic effect by combining selenium and silver with titanium nanotubes.

Recent Advances in Copper-Doped Titanium Implants

Titanium (Ti) and its alloys have been extensively used as implant materials in clinical practice due to their high corrosion resistance, light weight and excellent biocompatibility. However, the insufficient intrinsic osteogenic capacity of Ti and its alloys impedes bone repair and regeneration, and implant-related infection or inflammation remains the leading cause of implant failure. Bacterial infections or inflammatory diseases constitute severe threats to human health. The physicochemical properties of the material are critical to the success of clinical procedures, and the doping of Cu into Ti implants has been confirmed to be capable of enhancing the bone repair/regeneration, angiogenesis and antibacterial capability. This review outlines the recent advances in the design and preparation of Cu-doped Ti and Ti alloy implants, with a special focus on various methods, including plasma immersion implantation, magnetron sputtering, galvanic deposition, microarc oxidation and sol-gel synthesis. More importantly, the antibacterial and mechanical properties as well as the corrosion resistance and biocompatibility of Cu-doped Ti implants from different methods are systematically reviewed, and their prospects and limitations are also discussed.

Corrosion Behavior of Titanium Dental Implants with Implantoplasty

The procedure generally used to remove bacterial biofilm adhering to the surface of titanium on dental implants is implantoplasty. This treatment is based on the machining of the titanium surface to remove bacterial plaque. In this study, we used 60 grade 4 titanium implants and performed the implantoplasty protocol. Using X-ray diffraction, we determined the stresses accumulated in each of the as-received, machined and debris implants. The resistance to corrosion in open circuit and potentiodynamically in physiological medium has been determined, and the corrosion potentials and intensities have been determined. Tests have been carried out to determine ion release by ICP-MS at different immersion times. The results show that the corrosion resistance and the release of titanium ions into the medium are related to the accumulated energy or the degree of deformation. The titanium debris exhibit compressive residual stresses of −202 MPa, the implant treated with implantoplasty −120 MPa, and as-received −77 MPa, with their corrosion behavior resulting in corrosion rates of 0.501, 0.77, and 0.444 mm/year, respectively. Debris is the material with the worst corrosion resistance and the one that releases the most titanium ions to the physiological medium (15.3 ppb after 21 days vs. 7 ppb for as-received samples). Pitting has been observed on the surface of the debris released into the physiological environment. This behavior should be taken into account by clinicians for the good long-term behavior of implants with implantoplasty.

Antibacterial approaches in tissue engineering using metal ions and nanoparticles: From mechanisms to applications

Bacterial infection of implanted scaffolds may have fatal consequences and, in combination with the emergence of multidrug bacterial resistance, the development of advanced antibacterial biomaterials and constructs is of great interest. Since decades ago, metals and their ions had been used to minimize bacterial infection risk and, more recently, metal-based nanomaterials, with improved antimicrobial properties, have been advocated as a novel and tunable alternative. A comprehensive review is provided on how metal ions and ion nanoparticles have the potential to decrease or eliminate unwanted bacteria. Antibacterial mechanisms such as oxidative stress induction, ion release and disruption of biomolecules are currently well accepted. However, the exact antimicrobial mechanisms of the discussed metal compounds remain poorly understood. The combination of different metal ions and surface decorations of nanoparticles will lead to synergistic effects and improved microbial killing, and allow to mitigate potential side effects to the host. Starting with a general overview of antibacterial mechanisms, we subsequently focus on specific metal ions such as silver, zinc, copper, iron and gold, and outline their distinct modes of action. Finally, we discuss the use of these metal ions and nanoparticles in tissue engineering to prevent implant failure.

Microbial Adhesion and Biofilm Formation on Bioactive Surfaces of Ti-35Nb-7Zr-5Ta Alloy Created by Anodization

This study evaluated the microbial colonization (adhesion and biofilm) on modified surfaces of a titanium alloy, Ti-35Nb-7Zr-5Ta, anodized with Ca and P or F ions, with and without silver deposition. The chemical composition, surface topography, roughness (Ra), and surface free energy were evaluated before and after the surface modifications (anodizing). Adhesion and biofilm formation on saliva-coated discs by primary colonizing species (Streptococcus sanguinis, Streptococcus gordonii, Actinomyces naeslundii) and a periodontal pathogen (Porphyromonasgingivalis) were assessed. The surfaces of titanium alloys were modified after anodizing with volcano-shaped micropores with Ca and P or nanosized with F, both with further silver deposition. There was an increase in the Ra values after micropores formation; CaP surfaces became more hydrophilic than other surfaces, showing the highest polar component. For adhesion, no difference was detected for S. gordonii on all surfaces, and some differences were observed for the other three species. No differences were found for biofilm formation per species on all surfaces. However, S. gordonii biofilm counts on distinct surfaces were lower than S. sanguinis, A. naeslundii, and P. gingivalis on some surfaces. Therefore, anodized Ti-35Nb-7Zr-5Ta affected microbial adhesion and subsequent biofilm, but silver deposition did not hinder the colonization of these microorganisms.

The role of silver coating for arthroplasty components

Periprosthetic joint infection (PJI) is one of the most dreaded complications after arthroplasty surgery; thus numerous approaches have been undertaken to equip metal surfaces with antibacterial properties. Due to its antimicrobial effects, silver is a promising coating for metallic surfaces, and several types of silver-coated arthroplasty implants are in clinical use today. However, silver can also exert toxic effects on eukaryotic cells both in the immediate vicinity of the coated implants and systemically. In most clinically-used implants, silver coatings are applied on bulk components that are not in direct contact with bone, such as in partial or total long bone arthroplasties used in tumour or complex revision surgery. These implants differ considerably in the coating method, total silver content, and silver release rates. Safety issues, such as the occurrence of argyria, have been a cause for concern, and the efficacy of silver coatings in terms of preventing PJI is also controversial. The application of silver coatings is uncommon on parts of implants intended for cementless fixation in host bone, but this option might be highly desirable since the modification of implant surfaces in order to improve osteoconductivity can also increase bacterial adhesion. Therefore, an optimal silver content that inhibits bacterial colonization while maintaining osteoconductivity is crucial if silver were to be applied as a coating on parts intended for bone contact. This review summarizes the different methods used to apply silver coatings to arthroplasty components, with a focus on the amount and duration of silver release from the different coatings; the available experience with silver-coated implants that are in clinical use today; and future strategies to balance the effects of silver on bacteria and eukaryotic cells, and to develop silver-coated titanium components suitable for bone ingrowth. Cite this article: Bone Joint J 2021;103-B(3):423-429.

One-Step Liquid Phase Polymerization of HEMA by Atmospheric-Pressure Plasma Discharges for Ti Dental Implants

Dental implants can fail due to various factors, in which bad tissue integration is believed to have a significant role. Specific properties of the implant surface, such as its chemistry and roughness, are of paramount importance to address specific cell responses, such as the adsorption of proteins, as well as the adhesion and differentiation of cells, which are suitable for biomaterial and tissue engineering. In this study, an acrylate-containing coating was produced on titanium surfaces through the atmospheric pressure plasma treatment of a liquid precursor, 2-hydroxyethyl methacrylate. A hydrophilic coating was obtained, showing retention of the monomer chemistry as assessed by FTIR analysis and XPS. Enhanced fibroblast adhesion and decreased Staphylococcus aureus and Escherichia coli adhesion were recorded, showing that this is a suitable method to produce biocompatible coatings with a reduced bacterial adhesion.

Biofunctional Elements Incorporated Nano/Microstructured Coatings on Titanium Implants with Enhanced Osteogenic and Antibacterial Performance

Bone fracture is prevalent among athletes and senior citizens and may require surgical insertion of bone implants. Titanium (Ti) and its alloys are widely used in orthopedics due to its high corrosion resistance, good biocompatibility, and modulus compatible with natural bone tissues. However, bone repair and regrowth are impeded by the insufficient intrinsic osteogenetic capability of Ti and Ti alloys and potential bacterial infection. The physicochemical properties of the materials and nano/microstructures on the implant surface are crucial for clinical success and loading with biofunctional elements such as Sr, Zn, Cu, Si, and Ag into nano/microstructured TiO2 coating has been demonstrated to enhance bone repair/regeneration and bacterial resistance of Ti implants. In this review, recent advances in biofunctional element-incorporated nano/microstructured coatings on Ti and Ti alloy implants are described and the prospects and limitations are discussed.

New Bactericide Orthodonthic Archwire: NiTi with Silver Nanoparticles

A potential new bactericide treatment for NiTi orthodontic archwires based in the electrodeposition of silver nanoparticles on the surface was studied. Twenty-five archwires were treated by electrodeposition, obtaining nanoparticles of silver embedded on the archwire surface. These were evaluated in order to investigate the possible changes on the superelastic characteristics (critical temperatures and stresses), the nickel ion release, and the bacteria culture behavior. The chemical composition was analyzed by Energy Dispersive X-Ray Spectroscopy-microanalysis; the singular temperatures of the martensitic transformation were obtained by a flow calorimeter. Induced martensitic transformation stresses were obtained by mechanical testing apparatus. Nickel ion release was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) equipment using artificial saliva solution at 37 °C. Bacterial tests were studied with the most used oral bacterial strains: Streptococcus sanguinis and Lactobacillus salivarius. NiTi samples were immersed in bacterial suspensions for 2 h at 37 °C. Adhered bacteria were separated and seeded on agar plates: Tood-Hewitt (TH) and Man-Rogosa-Sharpe (MRS) for S. sanguinis and for L.salivarius, respectively. These were then incubated at 37 °C for 1 day and the colonies were analyzed. The results showed that the transformation temperatures and the critical stresses have not statistically significant differences. Likewise, nickel ion release at different immersion times in saliva at 37 °C does not present changes between the original and treated with silver nanoparticles archwires. Bacteria culture results showed that the reduction of the bacteria due to the presence to the nanoparticles of silver is higher than 90%. Consequently, the new treatment with nanoparticles of silver could be a good candidate as bactericidic orthodontic archwire.

Polyethylene Glycol Pulsed Electrodeposition for the Development of Antifouling Coatings on Titanium

Titanium dental implants are widely used for the replacement of damaged teeth. However, bacterial infections at the interface between soft tissues and the implant can impair the functionality of the device and lead to failure. In this work, the preparation of an antifouling coating of polyethylene glycol (PEG) on titanium by pulsed electrodeposition was investigated in order to reduce Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) adhesion while maintaining human fibroblast adhesion. Different pulsed conditions were prepared and characterized by contact angle, Focused Ion Beam (FIB), Fourier Transformed Infrared Spectroscopy in the Attenuated Total Reflectance mode (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). XPS tested fibronectin adsorption. S. aureus, E. coli and human fibroblast adhesion was tested in vitro in both mono and co-culture settings. Physicochemical characterization proved useful for confirming the presence of PEG and evaluating the efficiency of the coating methods. Fibronectin adsorption decreased for all of the conditions, but an adsorption of 20% when compared to titanium was maintained, which supported fibroblast adhesion on the surfaces. In contrast, S. aureus and E. coli attachment on coated surfaces decreased up to 90% vs. control titanium. Co-culture studies with the two bacterial strains and human fibroblasts showed the efficacy of the coatings to allow for eukaryotic cell adhesion, even in the presence of pre-adhered bacteria.

Antimicrobial Efficacy of Different Decontamination Methods as Tested on Dental Implants with Various Types of Surfaces

Background

Peri-implantitis is an inflammatory reaction affecting both hard and soft tissues surrounding dental implants. This pathological condition is caused by a polymicrobial aggressive biofilm that colonizes the implant and abutment surface at the peri-implant crevice level. The present in vitro study evaluated different methods of implant surface decontamination and assessed whether the type of the implant surface influences the results.

Material/Methods

The study was conducted in an in vitro model of peri-implantitis using 30 implants. The implants were divided into 3 equal groups based on the surface characteristics: machined-surface, sand-blasted and acid-etched, and HA-coated. Implants were coated with E. coli biofilm. After an incubation period, they were decontaminated with 4 different methods: sonic scaler application, sonic scaler application with the chemical agent Perisolv^® combination, Er: YAG laser treatment, and PDT therapy with methylene blue as a photosensitizer.

Results

The highest level of decontamination was achieved for machined-surface implants and for the combined chemical-mechanical and Er: YAG laser treatment.

Conclusions

The results of our study suggest that the method of implant decontamination should be customized to the type of implant surface.

Antimicrobial Electrodeposited Silver-Containing Calcium Phosphate Coatings

Biocompatible antimicrobial coatings may enhance the function of many orthopedic implants by combating infection. Hydroxyapatite is a choice mineral for such a coating as it is native to bone and silver would be a possible antimicrobial agent as it is also commonly used in biomedical applications. The aim of the research is to develop a silver-containing calcium phosphate (Ag/Ca-P) coating via electrochemical deposition on titanium substrates as this allows for controlled coating buildup on complex shapes and porous surfaces. Two different deposition approaches are explored: one-step Ag/Ca-P(1) deposition coatings, containing silver ions as microsized silver phosphate particles embedded in the Ca-P matrix; and via a two-step method (Ag/Ca-P(2)) where silver is deposited as metallic silver nanoparticle on the Ca-P coating. The Ag/Ca-P(1) coating displays a bacterial reduction of 76.1 ± 8.3% via Ag-ion leaching. The Ag/Ca-P(2) coating displays a bacterial reduction of 83.7 ± 4.5% via contact killing. Interestingly, by preincubation in phosphate-buffered saline solution, bacterial reduction improves to 97.6 ± 2.7 and 99.7 ± 0.4% for Ag/Ca-P(1) and Ag/Ca-P(2) coatings, respectively, due to leaching of formed AgCl_x^(x-1)- species. The biocompatibility evaluation indicates that the Ag/Ca-P(1) coating is cytotoxic towards osteoblasts while the Ag/Ca-P(2) coating shows excellent compatibility. The electrochemical deposition of highly bactericidal coatings with excellent biocompatibility will enable us to coat future bone implants even with complex or porous structures.

Comprehensive Evaluation of the Biological Properties of Surface-Modified Titanium Alloy Implants

An increasing interest in the fabrication of implants made of titanium and its alloys results from their capacity to be integrated into the bone system. This integration is facilitated by different modifications of the implant surface. Here, we assessed the bioactivity of amorphous titania nanoporous and nanotubular coatings (TNTs), produced by electrochemical oxidation of Ti6Al4V orthopedic implants' surface. The chemical composition and microstructure of TNT layers was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). To increase their antimicrobial activity, TNT coatings were enriched with silver nanoparticles (AgNPs) with the chemical vapor deposition (CVD) method and tested against various bacterial and fungal strains for their ability to form a biofilm. The biointegrity and anti-inflammatory properties of these layers were assessed with the use of fibroblast, osteoblast, and macrophage cell lines. To assess and exclude potential genotoxicity issues of the fabricated systems, a mutation reversal test was performed (Ames Assay MPF, OECD TG 471), showing that none of the TNT coatings released mutagenic substances in long-term incubation experiments. The thorough analysis performed in this study indicates that the TNT5 and TNT5/AgNPs coatings (TNT5-the layer obtained upon applying a 5 V potential) present the most suitable physicochemical and biological properties for their potential use in the fabrication of implants for orthopedics. For this reason, their mechanical properties were measured to obtain full system characteristics.

In vitro evaluation of a multispecies oral biofilm over antibacterial coated titanium surfaces

Peri-implantitis is an infectious disease that affects the supporting soft and hard tissues around dental implants and its prevalence is increasing considerably. The development of antibacterial strategies, such as titanium antibacterial-coated surfaces, may be a promising strategy to prevent the onset and progression of peri-implantitis. The aim of this study was to quantify the biofilm adhesion and bacterial cell viability over titanium disc with or without antibacterial surface treatment. Five bacterial strains were used to develop a multispecies oral biofilm. The selected species represent initial (Streptococcus oralis and Actinomyces viscosus), early (Veillonella parvula), secondary (Fusobacterium nucleatum) and late (Porphyromonas gingivalis) colonizers. Bacteria were sequentially inoculated over seven different types of titanium surfaces, combining different roughness level and antibacterial coatings: silver nanoparticles and TESPSA silanization. Biofilm formation, cellular viability and bacterial quantification over each surface were analyzed using scanning electron microscopy, confocal microscopy and real time PCR. Biofilm formation over titanium surfaces with different bacterial morphologies could be observed. TESPSA was able to significantly reduce the cellular viability when compared to all the surfaces (p < 0.05). Silver deposition on titanium surface did not show improved results in terms of biofilm adhesion and cellular viability when compared to its corresponding non-coated surface. The total amount of bacterial biofilm did not significantly differ between groups (p > 0.05). TESPSA was able to reduce biofilm adhesion and cellular viability. However, silver deposition on titanium surface seemed not to confer these antibacterial properties.

The relationship between substrate morphology and biological performances of nano-silver-loaded dopamine coatings on titanium surfaces

Biomedical device-associated infection (BAI) and lack of osseointegration are the main causes of implant failure. Therefore, it is imperative for implants not only to depress microbial activity and biofilm colonization but also to prompt osteoblast functions and osseointegration. As part of the coating development for implants, the interest of in vitro studies on the interaction between implant substrate morphology and the coating's biological performances is growing. In this study, by harnessing the adhesion and reactivity of bioinspired polydopamine, nano-silver was successfully anchored onto micro/nanoporous as well as smooth titanium surfaces to analyse the effect of substrate morphology on biological performances of the coatings. Compared with the smooth surface, a small size of nano-silver and high silver content was found on the micro/nanoporous surface. More mineralization happened on the coating on the micro/nanoporous structure than on the smooth surface, which led to a more rapid decrease of silver release from the micro/nanoporous surface. Antimicrobial tests indicated that both surfaces with resulting coating inhibit microbial colonization on them and growth around them, indicating that the coating eliminates the shortcoming of the porous structure which render the implant extremely susceptible to BAI. Besides, the multiple osteoblast responses of nano-silver-loaded dopamine coatings on both surfaces, i.e. attachment, proliferation and differentiation, have deteriorated, however the mineralized surfaces of these coatings stimulated osteoblast proliferation and differentiation, especially for the micro/nanoporous surface. Therefore, nano-silver-loaded dopamine coatings on micro/nanoporous substratum may not only reduce the risk of infection but also facilitate mineralization during the early post-operative period and then promote osseointegration owing to the good osteoblast-biocompatibility of the mineralized surface. These results clearly highlight the influence of the substrate morphology on the biological performances of implant coating.

Silver nanoparticles in dentistry

OBJECTIVE

Silver nanoparticles (AgNPs) have been extensively studied for their antimicrobial properties, which provide an extensive applicability in dentistry. Because of this increasing interest in AgNPs, the objective of this paper was to review their use in nanocomposites; implant coatings; pre-formulation with antimicrobial activity against cariogenic pathogens, periodontal biofilm, fungal pathogens and endodontic bacteria; and other applications such as treatment of oral cancer and local anesthesia. Recent achievements in the study of the mechanism of action and the most important toxicological aspects are also presented.

METHODS

Systematic searches were carried out in Web of Science (ISI), Google, PubMed, SciFinder and EspaceNet databases with the keywords "silver nano* or AgNP*" and "dentist* or dental* or odontol*".

RESULTS

A total of 155 peer-reviewed articles were reviewed. Most of them were published in the period of 2012-2017, demonstrating that this topic currently represents an important trend in dentistry research. In vitro studies reveal the excellent antimicrobial activity of AgNPs when associated with dental materials such as nanocomposites, acrylic resins, resin co-monomers, adhesives, intracanal medication, and implant coatings. Moreover, AgNPs were demonstrated to be interesting tools in the treatment of oral cancers due to their antitumor properties.

SIGNIFICANCE

The literature indicates that AgNPs are a promising system with important features such as antimicrobial, anti-inflammatory and antitumor activity, and a potential carrier in sustained drug delivery. However, there are some aspects of the mechanisms of action of AgNPs, and some important toxicological aspects arising from the use of this system that must be completely elucidated.

Evaluation of bone loss in antibacterial coated dental implants: An experimental study in dogs

The aim of this study was to evaluate the in vivo effect of antibacterial modified dental implants in the first stages of peri-implantitis. Thirty dental implants were inserted in the mandibular premolar sites of 5 beagle dogs. Sites were randomly assigned to Ti (untreated implants, 10units), Ti_Ag (silver electrodeposition treatment, 10units), and Ti_TSP (silanization treatment, 10units). Coated implants were characterized by scanning electron microscopy, interferometry and X-ray photoelectron spectroscopy. Two months after implant insertion, experimental peri-implantitis was initiated by ligature placement. Ligatures were removed 2months later, and plaque formation was allowed for 2 additional months. Clinical and radiographic analyses were performed during the study. Implant-tissue samples were prepared for micro computed tomography, backscattered scanning electron microscopy, histomorphometric and histological analyses and ion release measurements. X-ray, SEM and histology images showed that vertical bone resorption in treated implants was lower than in the control group (P<0.05). This effect is likely due to the capacity of the treatments to reduce bacteria colonization on the implant surface. Histological analysis suggested an increase of peri-implant bone formation on silanized implants. However, the short post-ligature period was not enough to detect differences in clinical parameters among implant groups. Within the limits of this study, antibacterial surface treatments have a positive effect against bone resorption induced by peri-implantitis.

Antibacterial coatings on titanium surfaces: a comparison study between in vitro single-species and multispecies biofilm

Dental plaque is a biofilm that causes dental caries, gingivitis, and periodontitis. Most of the studies in antibacterial coatings have been conducted by in vitro single-species biofilm formation, but oral biofilm involves more than 700 different bacterial species that are able to interact. Therefore, new studies are focused on in vitro multispecies biofilm models that mimic in vivo biofilms. The aim of the present work was to study different antibacterial coatings onto titanium surfaces and evaluate the in vitro antimicrobial properties of the surfaces on two different bacterial species and an oral biofilm. The lactate dehydrogenase assay determined that treated samples did not affect fibroblast viability. In addition, the viability of microorganisms on modified samples was evaluated by a LIVE/DEAD BacLight bacterial viability kit. Although a decrease in viable bacteria onto treated samples was obtained, the results showed differences in effectiveness when single-biofilm and oral plaque were tested. It confirms, as we expected, the distinct sensitivities that bacterial strains have. Thus, this multispecies biofilms model holds a great potential to assess antibacterial properties onto samples for dental purposes.