Biological and microbiological properties of low-modulus Ti-35Nb-4Ag alloy obtained by powder metallurgy for dental implant applications.

Objective

Stress shielding and bacterial infection are among the main challenges associated with metallic implants. To address these limitations, a Ti-35Nb-4Ag alloy was produced by powder metallurgy, combining a low elastic modulus (67.9 ± 1.1 GPa) with silver incorporated in solid solution to provide antibacterial activity.

Methods

Compression testing was performed to determine the elastic modulus. Roughness, wettability, and surface free energy with its dispersive and polar components were determined. The cytocompatibility study was carried out in accordance with ISO 10993-5, using commercially pure grade 4 titanium as a control. Adhesion and proliferation studies were carried out with human fibroblast cells (hFFS) for 2, 4, 7, and 14 days. Antibacterial studies were performed on three Gram-positive bacterial strains: Streptococcus gordonii, Staphylococcus aureus, and Enterococcus faecalis. The colonies formed (CFU) and the metabolic activity were assessed.

Results

The results showed that there were no statistically significant differences in roughness between the different metals tested. However, the Ti-35Nb-4Ag alloy had a lower contact angle (46°) than titanium (62°), and the surface energy was higher for the alloy (58 mJ/m²) than for titanium (41 mJ/m²). The increase in the polar component of the alloy (29 mJ/m2) compared to pure titanium (16 mJ/m2) was noteworthy. The alloy also showed enhanced fibroblast adhesion and proliferation while maintaining excellent cytocompatibility. In addition, the Ti-35Nb-4Ag alloy exhibited significantly lower CFU counts and bacterial metabolic activity than commercially pure titanium.

Significance

The Ti-35Nb-4Ag alloy combines a low elastic modulus, favourable surface properties, good cytocompatibility, and antibacterial activity, making it a promising candidate for hard tissue replacement.