Antibacterial and Cytocompatible: Combining Silver Nitrate with Strontium Acetate Increases the Therapeutic Window

Magnesium Infusion on Dental Implants and Its Impact on Osseointegration and Biofilm Development: A Review

Dental implants have gained global popularity as a treatment option for tooth loss. The success of dental implants depends on their optimal integration into the tissues of the alveolar bone and the periodontium. However, several factors can hinder the proper osseointegration of implants, with the growth of biofilm on the implant surface and subsequent peri-implant infections being significant concerns. To overcome this challenge, researchers have explored the incorporation of antimicrobial agents onto metallic implant surfaces to mitigate biofilm growth. Ideally these agents should promote osteogenesis while exhibiting antibacterial effects. Magnesium (Mg) has emerged as a promising dual-function implant coating due to its osteogenic and antibacterial properties. Despite several studies, the precise mechanisms behind osteoinductive and antimicrobial effect of Mg is unclear, as yet. This review aims to collate and discuss the utility of Mg as a dental implant coating, its impact on the osteogenic process, potential in mitigating microbial growth, and prospects for the future. A comprehensive literature search was conducted across several databases and the findings reveal the promise of Mg as a dual-function dental implant coating material, both as a standalone agent and in combination with other materials. The antibacterial effect of Mg is likely to be due to its (1) toxicity particularly at high concentrations, (2) the production or reactive oxygen species, and (3) pH modulation, while the osteoinductive effect is due to a complex series of cellular and biochemical pathways. Despite its potential both as a standalone and composite coating, challenges such as degradation rate, leaching, and long-term stability must be addressed. Further research is needed to understand the utility of Mg as an implant coating material, particularly in relation to its antibacterial activity, osseointegration, and longevity in the oral milieu.

Dual Antibacterial and Soft-Tissue-Integrative Effect of Combined Strontium Acetate and Silver Nitrate on Peri-Implant Environment: Insights from Multispecies Biofilms and a 3D Coculture Model

Creation of a biological seal and efficient antibacterial qualities in the peri-implant environment is essential for the success of dental implants. Therefore, novel multifunctional strategies are being developed to address these issues, aiming at the simultaneous improvement of tissue integration and hindering pathological biofilm formation. In this study, we investigated the effect of tissue-promotive strontium acetate (SrAc), antibacterial silver nitrate (AgNO3), and their combination on oral soft tissue cells and an oral multispecies biofilm not only in monoculture setups but also in a three-dimensional (3D) implant-tissue-oral bacterial-biofilm model (INTERbACT model) that takes the naturally occurring interactions into account. Application of SrAc led to improved fibroblast migration in the monoculture setting, without impairment of metabolic activity, even upon additional AgNO3 administration. Notably, the combined treatment of SrAc and AgNO3 resulted in a synergistic antibacterial effect during biofilm formation as well as on early matured biofilms. Most interestingly, the antibacterial effect of the combined treatment was even further enhanced within the coculture setup leading to increased bacterial death and decreased biofilm volume. The 3D tissue in the coculture setup underwent the combined treatment with a notable rise in CCL20 and IL-1β levels. Histologically, only the AgNO3-treated groups exhibited damage to the integrity of the epithelial barrier. Therefore, the results of this study demonstrated promising dual antibacterial and tissue-integrative characteristics of combined AgNO3 and SrAc in the dental implant environment. Additionally, the study emphasizes the importance of considering naturally occurring tissue-bacteria interactions for reliable in vitro testing of novel implant materials.

Exploring the role of strontium-based nanoparticles in modulating bone regeneration and antimicrobial resistance: a public health perspective

Strontium-based nanoparticles (SrNPs) have emerged as a versatile and promising class of nanomaterials with a wide range of potential applications in healthcare, particularly in the fields of bone regeneration and combating antimicrobial resistance (AMR). Recent research has highlighted the unique properties of SrNPs, including their ability to promote osteogenesis, enhance bone healing, and exhibit strong antimicrobial activity against multidrug-resistant pathogens. These attributes position SrNPs as innovative therapeutic agents with the potential to address challenges such as osteoporosis, bone infections, and the growing global AMR crisis. This comprehensive review critically examines the dual functional potential of SrNPs by analyzing their synthesis methods, physicochemical properties, biological interactions, and translational applications in orthopedic and antimicrobial therapies. Specifically, the review emphasizes SrNPs' ability to enhance bone density, accelerate fracture healing, and reduce the economic burden associated with prolonged treatment and rehabilitation for bone-related diseases. Furthermore, their novel application as antimicrobial agents is explored, highlighting their ability to target bacterial metabolic pathways and combat the rise of antibiotic resistance. The review focuses on the synthesis methods used for SrNPs, particularly co-precipitation, hydrothermal synthesis, and sol-gel techniques. Each method is explored for its ability to produce SrNPs with controlled size, shape, and functionality, while addressing their scalability, cost-effectiveness, and environmental impact. Additionally, the toxicological risks associated with SrNPs are also explored, emphasizing the need for comprehensive preclinical and clinical evaluations to ensure safety for humans and ecosystems. The regulatory and ethical landscape of SrNPs highlights the need for global safety protocols, equitable access, and international cooperation to ensure ethical nanotechnology use. Environmental fate studies address bioaccumulation risks and ecological concerns. This review identifies opportunities and challenges in advancing bone regenerative medicine and combating AMR while emphasizing sustainable and ethical SrNP development for researchers, policymakers, and stakeholders.

Biocompatibility and antibacterial activity of strontium and silver ion-releasing titanium with high silver treatment concentration

To overcome problems associated with surgical site infection and implant loosening, we developed a titanium (Ti)-based material employing a modified alkaline heat treatment that releases strontium (Sr) and silver (Ag) ions (CaSrAg-Ti). In this study, to determine the optimal Ag treatment concentration, we prepared four different materials-commercially pure Ti (cp-Ti) as a negative control, CaSr1mMAg-Ti, CaSr10mMAg-Ti, and CaSr50mMAg-Ti. Ion release test was performed by immersing the prepared disks in fetal bovine serum. With increased loading of Ag ions, the amount of released ions increased. Colony-forming unit count assay was performed using methicillin-susceptible Staphylococcus aureus and Escherichia coli. High antibacterial activity was observed in CaSr10mMAg-Ti and CaSr50mMAg-Ti groups. In vivo experiments were performed using the rat subcutaneous pocket infection model and evaluated by counting the attached bacteria, wound appearance, and histological evaluation. High antibacterial activity value (AAV >2) and anti-inflammatory effects were observed in the CaSr50mMAg-Ti group. However, CaSr10mMAg-Ti did not exhibit consistent antibacterial activity. For in vivo biocompatibility and bone-bonding ability evaluation, rods were implanted into the rat femur. No cytotoxicity was observed at 1 week, and good bone-bonding ability at 4 and 8 weeks was not significantly different from that of CaSr1mMAg-Ti. To evaluate in vivo bioactivity and cytotoxicity, MC3T3-E1 cells were cultured on disks. CaSr10mMAg-Ti and CaSr50mMAg-Ti significantly inhibited the proliferation and differentiation of MC3T3E1 cells, as well as the production of extracellular matrix in vivo, despite showing good biocompatibility in vivo. In conclusion, CaSr50mMAg-Ti, with increased Ag ion loading, exhibited high antibacterial activity in vivo while maintaining the bone-bonding ability and is a promising therapeutic biomaterial. Further research is needed to determine the optimal combination of therapeutic concentrations of Sr and Ag.

Ionic silver coating of orthopedic implants may impair osteogenic differentiation and mineralization

Silver (Ag) possesses potent antimicrobial properties and is used as a coating for medical devices. The impact of silver ions released from orthopedic implants on the differentiation and osteoid formation of different osteogenic cells has yet to be systematically studied. In the present study, human mesenchymal stem cells (hMSCs) and primary human osteoblasts (hOBs) were exposed to different static Ag+ concentrations (0, 0.5, 1.0 or 1.5 ppm) or dynamic Ag+ concentrations (range 0 to 0.7 ppm) that simulated the temporal release pattern from a Ag-nitrate coating of trabecular titanium (TLSN). Cell morphology was investigated by phase contrast and fluorescence microscopy. The activities of alkaline phosphatase (ALP) and lactate dehydrogenase, osteogenic gene expression (COL1A1, COL1A2 and ALPL), and osteoid deposition were examined for up to 4 weeks. DAPI and carboxyfluorescein diacetate staining revealed changes in the morphology of hOBs treated with ≥0.5 ppm Ag+, while osteocalcin-positive cells were observed primarily in the untreated group. Elevated Ag+ concentrations did not impact the production of ALP by either hMSCs or hOBs. Treatment with 1.5 ppm Ag+ or TLSN Ag+ led to a modest reduction in COL1A2 and ALPL levels in hMSCs at 2 weeks but not at 4 weeks nor in hOBs. In hMSC cultures, mineralization decreased at ≥1 ppm Ag+, whereas the same concentration range significantly reduced mineralization in hOB cultures. In conclusion, Ag+ concentrations ranging from 1.0 to 1.5 ppm may interfere with osteogenic differentiation, possibly by altering gene expression, thereby affecting mineralization. Only Ag+ concentrations up to 0.5 ppm allowed undisturbed osteogenic differentiation and mineralization. These findings pertain to creating Ag coatings of titanium intended for cementless fixation into host bone.

Osteoblast cell behavior on polyetheretherketone dental implant surfaces treated with different grit size aluminum oxide particles: An in vitro analysis

STATEMENT OF PROBLEM

The hydrophobic and bioinert nature of polyetheretherketone (PEEK) implants needs to be addressed for successful osseointegration.

PURPOSE

The purpose of this in vitro study was to evaluate the osteoblast cell behavior on PEEK implant surfaces treated with airborne-particle abrasion using different grit size aluminum oxide (Al2O3) particles.

MATERIAL AND METHODS

Disk-shaped specimens (n=96) were prepared from medical grade PEEK rods and were distributed into 4 groups (n=24) of untreated PEEK (PEEK 0), airborne-particle abrasion using 50-μm Al2O3 particles (PEEK 50), airborne-particle abrasion using 110-μm Al2O3 particles (PEEK 110), and airborne-particle abrasion using 150-μm Al2O3 particles (PEEK 150). The surface characteristics were assessed using water contact angle (WCA) measurements and scanning electron microscopy (SEM). MG-63 osteoblast cells were cultured, and the biocompatibility of PEEK was assessed using a CellTiter-blue cell viability assay and florescence staining at day 1, 3, and 7. The specimens were stained with Alizarin red to assess the osteoblast cell differentiation on day 10 and 14. The Levene test was used to test the homogeneity of variances. One-way and Welch ANOVA with post hoc corrections were used to assess the overall statistical significance of differences among the groups (α=.05).

RESULTS

The lowest mean WCA was demonstrated in PEEK 150 (49.25 ±5.51) and the highest in PEEK 0 (89.14 ±4.24) (P<.001). SEM images of PEEK 150 illustrated a more complex structure with a large area of globular outcroppings throughout the surface. PEEK 150 showed the highest cell metabolic activity at each time point with florescence staining showing a substantial cell confluence at day 3 and 7. Although PEEK 150 did not show a significant increase in cell proliferation, the number of cells attached was significantly higher than other groups (P<.05). PEEK 110 and 150 also showed a substantial increase in the extent of mineralization.

CONCLUSIONS

Airborne-particle abrasion using moderate Al2O3 grit size (110- or 150-μm) improved the hydrophilicity and osteoblast cell behavior on PEEK implants.

Effectiveness of strontium/silver-based titanium surface coatings in improving antibacterial and osteogenic implant characteristics: a systematic review of in-vitro studies

Introduction: Due to the high incidence of implant failures, dual functionalization of titanium surfaces with antibacterial and osteogenic agents, like silver (Ag) and strontium (Sr), has gained significant attention in recent years. However, so far, the combined antibacterial and osteoinductive effectiveness of Ag/Sr-based titanium surface coatings has only been analyzed in individual studies. Methods: This systematic review aims to evaluate the existing scientific literature regarding the PICOS question "Does dual incorporation of strontium/silver enhances the osteogenic and anti-bacterial characteristics of Ti surfaces in vitro?". As a result of a web-based search adhering to the PRISMA Guidelines using three electronic databases (PubMed, Scopus, and Web of Science) until March 31, 2023, a total of 69 publications were identified as potentially relevant and 17 of which were considered appropriate for inclusion into this review. Results and Discussion: In all included publications, the use of Sr/Ag combination showed enhanced osteogenic and antibacterial effects, either alone or in combination with other agents. Moreover, the combination of Sr and Ag shows potential to synergistically enhance these effects. Nevertheless, further studies need to validate these findings under clinically more relevant conditions and evaluate the mechanism of antimicrobial and osteogenic activity of Sr/Ag combination.

Silica-based silver nanocomposite 80S/Ag as Aggregatibacter actinomycetemcomitans inhibitor and its in vitro bioactivity

Background/purpose

As a commonly-found pathogen in periodontal disease, Aggregatibacter actinomycetemcomitans has been reported with several antibiotic resistance. Thus, to develop an alternative and protective therapy for A. actinomycetemcomitans infections is urgently needed in dentistry. In this study, we sought to synthesize a silica-based material to deliver silver nanoparticles for antibacterial purposes. Also, the bioactivities were examined via analyzing the formation of hydroxyapatite.

Materials and methods

The 80S/Ag powders were prepared by the evaporation-induced self-assembly method, with Si, Ca, P, and Ag composition ratios of 80, 15, 5, and 1/5/10 (mole percentage), respectively. The nitrogen adsorption-desorption isotherms, transmission electron microscope, selected area electron diffraction, and Fourier transform infrared spectroscopy were conducted for textural analyses. The disk diffusion test was carried out against A. actinomycetemcomitans strain ATCC 29523. In vitro bioactivity assessment involved soaking 80S/Ag membrane powders in acellular simulated body fluid.

Results

We successfully developed a material consisting of Si, Ca, P, and Ag, namely the 80S/Ag. In the antibacterial testing, the 80S/Ag demonstrated antibacterial activity against the commonly-found oral pathogen, A. actinomycetemcomitans, with a long-lasting effect for 168h. The formation of hydroxyapatite in simulated body fluid highlighted the characteristic of dentine remineralization for the 80S/Ag. The increased pH values after immersion in simulated body fluid would help neutralize the acidic oral environment.

Conclusion

Our results indicate that 80S/Ag possesses remarkable antibacterial properties, hydroxyapatite formation, and increased pH values after immersion in simulated body fluid, supporting the potential therapeutic application of 80S/Ag for treating periodontal disease.