Electrochemical methods to enhance osseointegrated prostheses

Surface modification strategies to reinforce the soft tissue seal at transmucosal region of dental implants

Soft tissue seal around the transmucosal region of dental implants is crucial for shielding oral bacterial invasion and guaranteeing the long-term functioning of implants. Compared with the robust periodontal tissue barrier around a natural tooth, the peri-implant mucosa presents a lower bonding efficiency to the transmucosal region of dental implants, due to physiological structural differences. As such, the weaker soft tissue seal around the transmucosal region can be easily broken by oral pathogens, which may stimulate serious inflammatory responses and lead to the development of peri-implant mucositis. Without timely treatment, the curable peri-implant mucositis would evolve into irreversible peri-implantitis, finally causing the failure of implantation. Herein, this review has summarized current surface modification strategies for the transmucosal region of dental implants with improved soft tissue bonding capacities (e.g., improving surface wettability, fabricating micro/nano topographies, altering the surface chemical composition and constructing bioactive coatings). Furthermore, the surfaces with advanced soft tissue bonding abilities can be incorporated with antibacterial properties to prevent infections, and/or with immunomodulatory designs to facilitate the establishment of soft tissue seal. Finally, we proposed future research orientations for developing multifunctional surfaces, thus establishing a firm soft tissue seal at the transmucosal region and achieving the long-term predictability of dental implants.

Effects of electrical stimulation with alternating fields on the osseointegration of titanium implants in the rabbit tibia - a pilot study

Introduction: Electrical stimulation has been used as a promising approach in bone repair for several decades. However, the therapeutic use is hampered by inconsistent results due to a lack of standardized application protocols. Recently, electrical stimulation has been considered for the improvement of the osseointegration of dental and endoprosthetic implants. Methods: In a pilot study, the suitability of a specifically developed device for electrical stimulation in situ was assessed. Here, the impact of alternating electric fields on implant osseointegration was tested in a gap model using New Zealand White Rabbits. Stimulation parameters were transmitted to the device via a radio transceiver, thus allowing for real-time monitoring and, if required, variations of stimulation parameters. The effect of electrical stimulation on implant osseointegration was quantified by the bone-implant contact (BIC) assessed by histomorphometric (2D) and µCT (3D) analysis. Results: Direct stimulation with an alternating electric potential of 150 mV and 20 Hz for three times a day (45 min per unit) resulted in improved osseointegration of the triangular titanium implants in the tibiae of the rabbits. The ratio of bone area in histomorphometry (2D analysis) and bone volume (3D analysis) around the implant were significantly increased after stimulation compared to the untreated controls at sacrifice 84 days after implantation. Conclusion: The developed experimental design of an electrical stimulation system, which was directly located in the defect zone of rabbit tibiae, provided feedback regarding the integrity of the stimulation device throughout an experiment and would allow variations in the stimulation parameters in future studies. Within this study, electrical stimulation resulted in enhanced implant osseointegration. However, direct electrical stimulation of bone tissue requires the definition of dose-response curves and optimal duration of treatment, which should be the subject of subsequent studies.

The biofilm removal effect and osteogenic potential on the titanium surface by electrolytic cleaning: An in vitro comparison of electrolytic parameters and five techniques

OBJECTIVES

To determine the optimal current and time of electrolytic cleaning (EC), compare its biofilm removal effect with generic treatments and evaluate the influence of EC to surface characteristics and osteogenic potential of SLA titanium (Ti) discs.

MATERIALS AND METHODS

The six-species biofilm-covered Ti discs were placed as cathodes in physiologic saline and subjected to various current and time treatments. The residual biofilms were evaluated to determine the optimal parameters. The contaminated Ti discs were randomized and treated by rotating Ti brush; ultrasonic-scaling with metal tips; ultrasonic-scaling with PEEK tips; air-polishing and EC. The residual biofilms were compared using a lipopolysaccharide kit (LPS), scanning electron microscope (SEM), confocal laser scanning microscopy and colony-forming unit counting. Non-contaminated Ti discs were treated and characterized. The bone marrow mesenchymal stem cells (BMSCs) were cultured on treated non-contaminated Ti discs. The adhesion, proliferation, alkaline phosphatase (ALP) activity and osteocalcin level of BMSCs were assessed.

RESULTS

The parameters at 0.6A5min were considered optimal. For LPS and SEM, EC promoted a significantly greater biofilm removal than the other groups. There were no changes in the Ti discs' colour, topography, roughness and chemical elements after EC, and the electrolysis-treated Ti discs obtained a super-hydrophilic surface. EC positively impacted the proliferation and ALP activity of BMSCs, surpassing the efficacy of alternative treatments.

CONCLUSIONS

EC achieves a near-complete eradication of contaminants on the SLA surface, causes no surface damage with improved hydrophilicity, and promotes the early osteogenic response of BMSCs, which makes it a promising treatment for peri-implantitis.

Cathodic voltage-controlled electrical stimulation and betadine decontaminate nosocomial pathogens from implant surfaces

Periprosthetic joint infection (PJI) after total joint arthroplasty is a major concern requiring multiple surgeries and antibiotic interventions. Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli are the predominant causes of these infections. Due to biofilm formation, antibiotic treatment for patients with PJI can prolong resistance, further complicating the use of current treatments. Previous research has shown that cathodic voltage-controlled electrical stimulation (CVCES) is an effective technique to prevent/treat implant-associated biofilm infections on titanium (Ti) surfaces. This study thus evaluated the efficacy of CVCES via the use of 10% betadine alone and in combination with CVCES to eradicate lab-grown biofilms on cemented and cementless cobalt-chromium (CoCr) and Ti surfaces. CVCES treatment alone for 24 hours demonstrated no detectable CFU for E. coli and P. aeruginosa biofilms on cementless CoCr implants. In the presence of cement, E. coli biofilms had 106 CFUs/implant remaining after CVCES treatment alone; however, P. aeruginosa biofilms on cemented implants were reduced to below detectable limits. The use of 10% betadine treatment for 3 minutes followed by 24-hour CVCES treatment brought CFU levels to below detectable limits in E. coli and P. aeruginosa. The same was true for S. aureus biofilms on cementless patellofemoral implants as well as femoral and tibial implants. These treatment methods were not sufficient for eradication of S. aureus biofilms on cemented implants. These results suggest that CVCES alone and CVCES with 10% betadine are effective approaches to treating biofilms formed by certain bacterial species potentially leading to the treatment of PJI.IMPORTANCEPeriprosthetic joint infections (PJIs) are problematic due to requiring multiple surgeries and antibiotic therapies that are responsible for increased patient morbidity and healthcare costs. These infections become resistant to antibiotic treatment due to the formation of biofilms on the orthopedic surfaces. Cathodic voltage-controlled electrical stimulation (CVCES) has previously been shown to be an effective technique to prevent and treat biofilm infections on different surfaces. This study shows that CVCES can increase the efficacy of 10% betadine irrigation used in debridement, antibiotics, and implant retention by 99.9% and clear infection to below detection limits. PJI treatments are at times limited, and CVCES could be a promising technology to improve patient outcomes.

In vitro and in vivo assessment of extended duration cathodic voltage-controlled electrical stimulation for treatment of orthopedic implant-associated infections

Effective treatment of orthopedic implant-associated infections (IAIs) remains a clinical challenge. The in vitro and in vivo studies presented herein evaluated the antimicrobial effects of applying cathodic voltage-controlled electrical stimulation (CVCES) to titanium implants inoculated with preformed bacterial biofilms of methicillin-resistant Staphylococcus aureus (MRSA). The in vitro studies showed that combining vancomycin therapy (500 µg/mL) with application of CVCES at -1.75 V (all voltages are with respect to Ag/AgCl unless otherwise stated) for 24 h resulted in 99.98% reduction in the coupon-associated MRSA colony-forming units (CFUs) (3.38 × 103 vs. 2.14 × 107 CFU/mL, p < 0.001) and a 99.97% reduction in the planktonic CFU (4.04 × 104 vs. 1.26 × 108 CFU/mL, p < 0.001) as compared with the no treatment control samples. The in vivo studies utilized a rodent model of MRSA IAIs and showed a combination of vancomycin therapy (150 mg/kg twice daily) with CVCES of -1.75 V for 24 h had significant reductions in the implant associated CFU (1.42 × 101 vs. 1.2 × 106 CFU/mL, p < 0.003) and bone CFU (5.29 × 101 vs. 4.48 × 106 CFU/mL, p < 0.003) as compared with the untreated control animals. Importantly, the combined 24 h CVCES and antibiotic treatments resulted in no implant-associated MRSA CFU enumerated in 83% of the animals (five out of six animals) and no bone-associated MRSA CFU enumerated in 50% of the animals (three out of six animals). Overall, the outcomes of this study have shown that extended duration CVCES therapy is an effective adjunctive therapy to eradicate IAIs.

Activity of a hypochlorous acid-producing electrochemical bandage as assessed with a porcine explant biofilm model

The activity of a hypochlorous acid-producing electrochemical bandage (e-bandage) in preventing methicillin-resistant Staphylococcus aureus infection (MRSA) infection and removing biofilms formed by MRSA was assessed using a porcine explant biofilm model. e-Bandages inhibited S. aureus infection (p = 0.029) after 12 h (h) of exposure and reduced 3-day biofilm viable cell counts after 6, 12, and 24 h exposures (p = 0.029). Needle-type microelectrodes were used to assess HOCl concentrations in explant tissue as a result of e-bandage treatment; toxicity associated with e-bandage treatment was evaluated. HOCl concentrations in infected and uninfected explant tissue varied between 30 and 80 µM, decreasing with increasing distance from the e-bandage. Eukaryotic cell viability was reduced by an average of 71% and 65% in fresh and day 3-old explants, respectively, when compared to explants exposed to nonpolarized e-bandages. HOCl e-bandages are a promising technology that can be further developed as an antibiotic-free treatment for wound biofilm infections.

Electrical stimulation to promote osseointegration of bone anchoring implants: a topical review

Electrical stimulation has shown to be a promising approach for promoting osseointegration in bone anchoring implants, where osseointegration defines the biological bonding between the implant surface and bone tissue. Bone-anchored implants are used in the rehabilitation of hearing and limb loss, and extensively in edentulous patients. Inadequate osseointegration is one of the major factors of implant failure that could be prevented by accelerating or enhancing the osseointegration process by artificial means. In this article, we reviewed the efforts to enhance the biofunctionality at the bone-implant interface with electrical stimulation using the implant as an electrode. We reviewed articles describing different electrode configurations, power sources, and waveform-dependent stimulation parameters tested in various in vitro and in vivo models. In total 55 English-language and peer-reviewed publications were identified until April 2020 using PubMed, Google Scholar, and the Chalmers University of Technology Library discovery system using the keywords: osseointegration, electrical stimulation, direct current and titanium implant. Thirteen of those publications were within the scope of this review. We reviewed and compared studies from the last 45 years and found nonuniform protocols with disparities in cell type and animal model, implant location, experimental timeline, implant material, evaluation assays, and type of electrical stimulation. The reporting of stimulation parameters was also found to be inconsistent and incomplete throughout the literature. Studies using in vitro models showed that osteoblasts were sensitive to the magnitude of the electric field and duration of exposure, and such variables similarly affected bone quantity around implants in in vivo investigations. Most studies showed benefits of electrical stimulation in the underlying processes leading to osseointegration, and therefore we found the idea of promoting osseointegration by using electric fields to be supported by the available evidence. However, such an effect has not been demonstrated conclusively nor optimally in humans. We found that optimal stimulation parameters have not been thoroughly investigated and this remains an important step towards the clinical translation of this concept. In addition, there is a need for reporting standards to enable meta-analysis for evidence-based treatments.

Comparisons of the killing effect of direct current partially mediated by reactive oxygen species on Porphyromonas gingivalis and Prevotella intermedia in planktonic state and biofilm state - an in vitro study

Background/purpose

Bacterial biofilms formed on the surface of tissues and biomaterials are major causes of chronic infections in humans. Among them, Porphyromonas gingivalis (P. gingivalis) and Prevotella intermedia (P. intermedia) are anaerobic pathogens causing dental infections associated with periodontitis. In this study, we evaluated the killing effect and underlying mechanisms of direct current (DC) as an antimicrobial method in vitro.

Materials and methods

We chose P. gingivalis and P. intermedia in different states to make comparisons of the killing effect of DC. By viable bacteria counting, fluorescent live/dead staining, reactive oxygen species (ROS) assay, addition of ROS scavenger DMTU and mRNA expression assay of ROS scavenging genes, the role of ROS in the killing effect was explored.

Results

The planktonic and biofilm states of two bacteria could be effectively killed by low-intensity DC. For the killing effect of 1000 μA DC, there were significant differences whether on planktonic P. gingivalis and P. intermedia (mean killing values: 2.40 vs 2.62 log₁₀ CFU/mL) or on biofilm state of those (mean killing values: 0.63 vs 0.98 log₁₀ CFU/mL). 1000 μA DC greatly induced ROS production and the mRNA expression of ROS scavenging genes. DMTU could partially decrease the killing values of DC and downregulate corresponding gene’s expression.

Conclusion

1000 μA DC can kill P. gingivalis and P. intermedia in two states by promoting overproduction of ROS, and P. intermedia is more sensitive to DC than P. gingivalis. These findings indicate low-intensity DC may be a promising approach in treating periodontal infections.

Bio-clickable mussel-inspired peptides improve titanium-based material osseointegration synergistically with immunopolarization-regulation

Upon the osteoporotic condition, sluggish osteogenesis, excessive bone resorption, and chronic inflammation make the osseointegration of bioinert titanium (Ti) implants with surrounding bone tissues difficult, often lead to prosthesis loosening, bone collapse, and implant failure. In this study, we firstly designed clickable mussel-inspired peptides (DOPA-N3) and grafted them onto the surfaces of Ti materials through robust catechol-TiO₂ coordinative interactions. Then, two dibenzylcyclooctyne (DBCO)-capped bioactive peptides RGD and BMP-2 bioactive domain (BMP-2) were clicked onto the DOPA-N3-coated Ti material surfaces via bio-orthogonal reaction. We characterized the surface morphology and biocompatibility of the Ti substrates and optimized the osteogenic capacity of Ti surfaces through adjusting the ideal ratios of BMP-2/RGD at 3:1. In vitro, the dual-functionalized Ti substrates exhibited excellent promotion on adhesion and osteogenesis of mesenchymal stem cells (MSCs), and conspicuous immunopolarization-regulation to shift macrophages to alternative (M2) phenotypes and inhibit inflammation, as well as enhancement of osseointegration and mechanical stability in osteoporotic rats. In summary, our biomimetic surface modification strategy by bio-orthogonal reaction provided a convenient and feasible method to resolve the bioinertia and clinical complications of Ti-based implants, which was conducive to the long-term success of Ti implants, especially in the osteoporotic or inflammatory conditions.

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A clickable mussel-inspired peptide and two DBCO-capped bioactive peptides for facile decoration of Ti prostheses via robust catechol/TiO2 coordinative interactions and click chemical reaction.

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Dual functionalized Ti-based surface can improve cell anchoring and osteogenicitity by rationally adjusting the grafting ratio of BMP-2 and RGD peptides.

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Dual functionalized Ti-based surface synergistically achieve M2 shifting and efficient inflammation inhibition for osseointegration.

Enhancing osteoblast survival through pulsed electrical stimulation and implications for osseointegration

Electrical stimulation has been suggested as a means for promoting the direct structural and functional bonding of bone tissue to an artificial implant, known as osseointegration. Previous work has investigated the impact of electrical stimulation in different models, both in vitro and in vivo, using various electrode configurations for inducing an electric field with a wide range of stimulation parameters. However, there is no consensus on optimal electrode configuration nor stimulation parameters. Here, we investigated a novel approach of delivering electrical stimulation to a titanium implant using parameters clinically tested in a different application, namely peripheral nerve stimulation. We propose an in vitro model comprising of Ti6Al4V implants precultured with MC3T3-E1 preosteoblasts, stimulated for 72 h at two different pulse amplitudes (10 µA and 20 µA) and at two different frequencies (50 Hz and 100 Hz). We found that asymmetric charge-balanced pulsed electrical stimulation improved cell survival and collagen production in a dose-dependent manner. Our findings suggest that pulsed electrical stimulation with characteristics similar to peripheral nerve stimulation has the potential to improve cell survival and may provide a promising approach to improve peri-implant bone healing, particularly to neuromusculoskeletal interfaces in which implanted electrodes are readily available.

Evaluating the Effectiveness of Biophysical Methods of Osteogenesis Stimulation: Review

Background. Stimulation of osteogenesis (SO) by biophysical methods has been widely used in practice to accelerate healing or stimulate the healing of fractures with non-unions, since the middle of the XIX century. SO can be carried out by direct current electrostimulation, or indirectly by low-intensity pulsed ultrasound, capacitive electrical coupling stimulation, and pulsed electromagnetic field stimulation. SO simulates natural physiological processes: in the case of electrical stimulation, it changes the electromagnetic potential of damaged cell tissues in a manner similar to normal healing processes, or in the case of low-intensity pulsed ultrasound, it produces weak mechanical effects on the fracture area. SO increases the expression of factors and signaling pathways responsible for tissue regeneration and bone mineralization and ultimately accelerates bone union.The purpose of this review was to present the most up-to-date data from laboratory and clinical studies of the effectiveness of SO.Material and Methods. The results of laboratory studies and the final results of metaanalyses for each of the four SO methods published from 1959 to 2020 in the PubMed, EMBASE, and eLibrary databases are reviewed.Conclusion. The use of SO effectively stimulates the healing of fractures with the correct location of the sensors, compliance with the intensity and time of exposure, as well as the timing of use for certain types of fractures. In case of non-union or delayed union of fractures, spondylodesis, arthrodesis, preference should be given to non-invasive methods of SO. Invasive direct current stimulation can be useful for non-union of long bones, spondylodesis with the risk of developing pseudoarthrosis.

Evaluating the Effectiveness of Biophysical Methods of Osteogenesis Stimulation: Review

Background. Stimulation of osteogenesis (SO) by biophysical methods has been widely used in practice to accelerate healing or stimulate the healing of fractures with non-unions, since the middle of the XIX century. SO can be carried out by direct current electrostimulation, or indirectly by low-intensity pulsed ultrasound, capacitive electrical coupling stimulation, and pulsed electromagnetic field stimulation. SO simulates natural physiological processes: in the case of electrical stimulation, it changes the electromagnetic potential of damaged cell tissues in a manner similar to normal healing processes, or in the case of low-intensity pulsed ultrasound, it produces weak mechanical effects on the fracture area. SO increases the expression of factors and signaling pathways responsible for tissue regeneration and bone mineralization and ultimately accelerates bone union.The purpose of this review was to present the most up-to-date data from laboratory and clinical studies of the effectiveness of SO.Material and Methods. The results of laboratory studies and the final results of metaanalyses for each of the four SO methods published from 1959 to 2020 in the PubMed, EMBASE, and eLibrary databases are reviewed.Conclusion. The use of SO effectively stimulates the healing of fractures with the correct location of the sensors, compliance with the intensity and time of exposure, as well as the timing of use for certain types of fractures. In case of non-union or delayed union of fractures, spondylodesis, arthrodesis, preference should be given to non-invasive methods of SO. Invasive direct current stimulation can be useful for non-union of long bones, spondylodesis with the risk of developing pseudoarthrosis.