Unraveling the antimicrobial mechanisms and multifunctional performance of boron-doped glass coatings on dental zirconias

To evaluate the mechanical, antimicrobial, and optical properties of boron-doped soda-lime glass coatings on 3Y-TZP and 5Y-PSZ zirconia. Disc-shaped specimens of 3Y-TZP and 5Y-PSZ were divided into: as-sintered (3Y-C and 5Y-C), coated with commercial glaze (3Y-G and 5Y-G), with soda-lime glass (3Y-SL and 5Y-SL), and with silver-containing soda-lime glass (3Y-SLAg and 5Y-SLAg). Cytotoxicity (MTT assay), biaxial flexural strength (σB), X-ray diffraction (XRD), translucency (TP00), color difference (ΔE00), and roughness (Ra and Rz) were conducted. Biofilm formation was quantified by colony-forming units (CFU/mL) of C. albicans, S. sanguinis, and E. coli. Scanning electron microscopy (SEM) and fractography were conducted. Energy-dispersive X-ray diffraction (EDS) was performed on SL and SLAg samples. Weibull modulus (m) and characteristic strength (σ0) for biaxial flexural strength (95 % CI) were calculated. All data were analyzed by two-way ANOVA, and Dunn's method, while the CFU test was analyzed by one-way ANOVA (α = 0.05). The experimental glasses did not induce cytotoxic effects. The flexural strength of 3Y-TZP groups showed highest values: 3Y-C(847.45 MPa); 3Y-G(843.22 MPa); 3Y-SL(806.41 MPa); 3Y-SLAg(769.04 MPa); 5Y-G(589.77 MPa); 5Y-SLAg (576.20 MPa); 5Y-C(479.44 MPa); 5Y-SL(474.00 MPa). Diffractograms showed tetragonal and cubic phases for all groups. Higher translucency values were observed for 5Y-PSZ groups, while for ΔE00 were similar. The SL and SLAg groups exhibited the lowest roughness values (Ra) for both zirconia. The 5Y-SL group exhibited antimicrobial effects against all tested microorganisms, while the 5Y-SLAg group showed antimicrobial effects against E. coli. Fractures originated at the zirconia surface, while for the 5Y-G group at the glaze layer. SEM micrographs revealed flower-shaped crystals for 3Y-SL, 5Y-SL and 5Y-SLAg groups. EDS identified zirconia in the crystal's composition. The 5Y-SL group exhibited a significant antimicrobial effect. This cytocompatible glass (5Y-SL) provided a superior antibiofilm effect compared to 5Y-SLAg. Moreover, the mechanical and optical properties of both 5Y-PSZ and 3Y-TZP zirconia were maintained.