Bioactive Glass Modified with Zirconium Incorporation for Dental Implant Applications: Fabrication, Structural, Electrical, and Biological Analysis

Abstract

Implantology is crucial for restoring aesthetics and masticatory function in oral rehabilitation. Despite its advantages, certain issues, such as bacterial infection, may still arise that hinder osseointegration and result in implant rejection. This work aims to address these challenges by developing a biomaterial for dental implant coating based on 45S5 Bioglass^® modified by zirconium insertion. The structural characterization of the glasses, by XRD, showed that the introduction of zirconium in the Bioglass network at a concentration higher than 2 mol% promotes phase separation, with crystal phase formation. Impedance spectroscopy was used, in the frequency range of 10²-10⁶ Hz and the temperature range of 200-400 K, to investigate the electrical properties of these Bioglasses, due to their ability to store electrical charges and therefore enhance the osseointegration capacity. The electrical study showed that the presence of crystal phases, in the glass ceramic with 8 mol% of zirconium, led to a significant increase in conductivity. In terms of biological properties, the Bioglasses exhibited an antibacterial effect against Gram-positive and Gram-negative bacteria and did not show cytotoxicity for the Saos-2 cell line at extract concentrations up to 25 mg/mL. Furthermore, the results of the bioactivity test revealed that within 24 h, a CaP-rich layer began to form on the surface of all the samples. According to our results, the incorporation of 2 mol% of ZrO₂ into the Bioglass significantly improves its potential as a coating material for dental implants, enhancing both its antibacterial and osteointegration properties.

Keywords: Bioglass®; antibacterial properties; bioactivity; dielectric properties; implant coating; osseointegration; zirconium.

Figure 1

XRD patterns of 45S5 Bioglass samples modified by the insertion of various amounts of ZrO₂.

Figure 2

FTIR spectra of 45S5 Bioglass samples modified by ZrO₂ insertion.

Figure 3

(a) DTA spectrum of the Zr2 and Zr8 samples and (b) XRD patterns of Zr2 and Zr8 after thermal treatment at 800 °C for 6 h.

Figure 4

AC conductivity versus 1000/T at 10 kHz (inset: magnification of the high-temperature measurement zone; the lines reflect the Arrhenius fit).

Figure 5

The dielectric constant, ε’, as a function of the temperature of the Bioglass samples modified by ZrO₂ insertion at 10 kHz (the inset is the magnification of the blue rectangle region).

Figure 6

The imaginary part of the dielectric modulus, M″, versus the frequency for the Zr2 sample.

Figure 7

The normalized imaginary part of the modulus M″/M″max versus the frequency at 380 K for the Bioglass samples modified by ZrO₂ insertion.

Figure 8

Relative viability of (a) non-passivated and (b) passivated Bioglass extracts modified by ZrO₂ in culture with Saos-2 cells. C+ and C− represent the positive control (cells in a cytotoxic environment) and negative control (viable cells).

Figure 9

Measurements of inhibition halo diameter of the Bioglass samples against E. coli, S. aureus, and S. mutans bacteria after incubation for 24 h. The results are reported as the mean ± SD. The asterisks indicate significance in an unpaired t-test; * p ≤ 0.05; ** p ≤ 0.01; **** p ≤ 0.0001, ns: nonsignificant. The image on the right side is an example of an assay plate illustrating the inhibition halo of the Zr2 pellet on S. aureus.

Figure 10

The variation in the concentration of (a) Si and (b) Na and (c) the Ca/P ratio on the Bioglass pellets’ surfaces after soaking in SB F.

Figure 11

The variation in the pH of the SBF solution with the immersion time.

Figure 12

SEM micrographs of the Bioglasses containing various concentrations of ZrO₂ after immersion in SBF for: (a1–a4) 0 d; (b1–b4) 1 d; (c1–c4) 4 d; (d1–d4) 14 d. (The magnification of the SEM images is 10 kX).