Antibacterial and Antibiofilm Activity of Layers Enriched with Silver Nanoparticles on Orthodontic Microimplants

Orthodontic microimplants have revolutionized anchorage in orthodontics but remain vulnerable to microbial colonization, potentially leading to infection and failure. Surface modifications incorporating silver nanoparticles (AgNPs) offer antimicrobial benefits, providing long-term protection against bacterial infections, while improving partial osseointegration. This study investigates hybrid coatings enriched with AgNPs, calcium (Ca), and phosphorus (P) to improve antimicrobial efficacy and reduce biofilm formation. Microimplants fabricated from the Ti6Al4V alloy were divided into six groups with varying surface treatments, including etching in hydrofluoric acid and hybrid layers containing 0.5 mol% AgNPs and CaP. Antibacterial activity was evaluated using agar diffusion and biofilm formation assays against <i>S. aureus</i>, <i>E. coli</i>, and <i>S. mutans</i>. Surface roughness was analyzed and correlated with biofilm formation. The model assessing the impact of biomaterials on <i>S. aureus</i> biofilm revealed a strong association (R² = 0.94), with biomaterial choice significantly influencing biofilm formation. The model for <i>E. coli</i> biofilm exhibited exceptional predictability (R² = 0.99). The model for <i>S. mutans</i> biofilm demonstrated an association (R² = 0.68). Hybrid coatings exhibited a promising antimicrobial activity. Biofilm formation was higher on microimplants with rougher surfaces. Hybrid coatings enriched with AgNPs and CaP enhance antimicrobial properties and partially reduce biofilm formation. It is suggested that the optimization of microimplant surface areas varies according to function. An enhanced performance can be achieved by maintaining a smooth surface for soft tissue contact, while incorporating a rough surface enriched with bactericidal and bioactive modifiers for bone contact areas.