1 Introduction
Dental implants are fundamental to contemporary restorative dentistry, providing an exceptional solution for individuals experiencing tooth loss due to aging, trauma, or disease. The global demand for dental implants has increased significantly, driven by an aging population, increased awareness of oral health, and advancements in implant technology. These implants are essential for restoring oral function, aesthetics, and overall quality of life, making them a primary focus in biomedical research (Addy, 2024; Cociuban et al., 2024). Despite significant progress, the long-term efficacy of dental implants remains uncertain. Osseointegration, the biological process through which the implant integrates with surrounding bone tissue, is crucial for stability and functionality. Titanium and its alloys, particularly Ti-6Al-4V, are widely used for their superior mechanical properties and corrosion resistance. However, they may have limitations in facilitating osseointegration (Civantos et al., 2017; Silva et al., 2022). Insufficient bone integration can lead to micromotion and gaps at the implant-bone interface, which may promote bacterial adhesion and biofilm formation. Once established, these biofilms can induce persistent infections and localized bone resorption, ultimately threatening implant success (Gbejuade et al., 2015; Davidson et al., 2019).
To address these limitations, researchers are exploring bioactive materials and coatings promoting osseointegration while reducing bacterial colonization risk. One of the most promising materials is 45S5 Bioglass® (46.1SiO2-24.4Na2O-26.9CaO-2.6P2O5 (mol%)), which gained significant attention for its ability to promote bone regeneration (Hench et al., 1971; Hench and Paschall, 1973). Initially developed in the 1970s by Larry L. Hench (Hench, 2006; Hench, 2013), these glasses possess a unique composition that allows them to bond directly to living bone tissue. Upon contact with physiological fluids, 45S5 Bioglass® undergoes a series of reactions, leading to the formation of a hydroxyapatite layer on its surface. This layer mimics the mineral component of natural bone, facilitating osseointegration. Additionally, the release of ions from the glass can inhibit bacterial growth, reducing the risk of infection (Allan et al., 2001; Allan et al., 2002; Begum et al., 2016).
The incorporation of metal ions into bioglass has emerged as a promising strategy to enhance its biological properties (Cacciotti, 2017; de Souza Balbinot et al., 2019; Malavasi et al., 2019; Aghili et al., 2022; Hammami et al., 2024). Elements such as zirconium (Zr) and iron (Fe) have garnered significant attention due to their unique characteristics. Zirconium, particularly in the form of zirconium dioxide (ZrO2), is extensively utilized in biomedical applications due to its biocompatibility and outstanding mechanical properties, including its exceptional strength and fracture toughness, making it a widely used reinforcing agent (Silva et al., 2004; Pattnaik et al., 2011; Bhowmick et al., 2017; Kang et al., 2021). Zr can also stimulate osteoblast proliferation and differentiation, leading to accelerated bone healing (Hempel et al., 2010; Pattnaik et al., 2011; Bhowmick et al., 2017). Studies by Goo et al. (2018) and Sa et al. (2018) have demonstrated the effectiveness of ZrO2 in promoting bone formation and improving osteogenic activity, respectively. Additionally, ZrO2 possesses significant antimicrobial properties against various bacteria by interfering with bacterial respiration processes (Jangra et al., 2012; Fathima et al., 2017; Rad Goudarzi et al., 2019; Kumar et al., 2020).
Iron (Fe) is essential for various cellular functions, including oxygen transport and energy metabolism (Touati, 2000; Theil and Goss, 2009). Iron deficiency can lead to impaired collagen synthesis and reduced bone density (Abraham, 2014; Bose et al., 2018). Fe supports osteoblastic differentiation, proliferation, and calcification (Ullah et al., 2020; Zhu et al., 2023). Research by Long et al. (2014) and Zhou et al. (2024) has shown that incorporating Fe into biomaterials enhances cell adhesion, proliferation, and osteogenic differentiation. Fe also exhibits antibacterial properties by generating reactive oxygen species (ROS) through the Fenton reaction, which can damage bacterial cells (Touati, 2000; Behera et al., 2012; Zhang et al., 2016; Ezealigo et al., 2021).
In addition to ion insertion, electrical polarization offers a promising approach to enhance the biological properties of bioactive glass. By applying an electric field, surface charges can be induced, influencing cellular interactions and promoting tissue integration (Metwally and Stachewicz, 2019). This approach has been successfully applied to calcium-phosphate ceramics like hydroxyapatite (HA), where negative surface charges have been shown to promote bone growth and cell proliferation (Yamashita et al., 1996; Kobayashi et al., 2001; Ohgaki et al., 2001). However, the application of electrical polarization to bioglasses remains relatively unexplored. While the electrical polarization of HA is primarily driven by proton migration (Prezas et al., 2017), the higher ionic conductivity of bioglasses, mainly due to sodium ions, suggests that ion migration may play a significant role in their polarization (Obata et al., 2003; Obata et al., 2004). A deeper understanding of the electrical properties of bioglass is crucial to unlock their potential for electrical polarization, which can significantly enhance their bioactivity and overall performance in biomedical applications.
This study addresses a significant challenge in dental implantology: bacterial infections that can lead to bone loss and subsequent implant failure. To mitigate this issue, we developed a material for implant coating based on 45S5 bioglass®, incorporating varying concentrations of zirconium dioxide (ZrO2) and magnetite (Fe3O4). The melt-quenching technique used in this study offers significant advantages in terms of scaling up the production of these materials for clinical use. This method allows for the fabrication of bioactive glasses in large quantities at a relatively low cost compared to other techniques, such as sol-gel. Its reliability and efficiency make it a promising approach for large-scale production, which is essential for practical applications in clinical settings. The influence of these metal oxides on the structural properties of 45S5 bioglass was examined using X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and Raman spectroscopy. Given bioglass’s potential for electrical charge storage, impedance spectroscopy (IS) was employed to investigate its electrical properties and the impact of oxide additions. To evaluate the potential of the prepared glasses as implant coating materials, a cytotoxicity assay was conducted using the extract method and human osteosarcoma (Saos-2) cells. The antibacterial activity of the different bioglass compositions was assessed using the agar diffusion method against Escherichia coli, Staphylococcus aureus, and Streptococcus mutans. The bioactivity assay was assessed by immersing the samples in a Simulated Body Fluid (SBF) solution.
