Antimicrobial properties of copper-based shape-memory alloy wires coupled to hydrogen peroxide solutions for endodontic treatments

AIMS: Copper-rich shape memory alloys (Cu-SMAs) combine unique mechanical properties and catalytic redox activity, supporting the development of advanced endodontic files to improve patient treatments. This study evaluated the bactericidal activity of CuAlBe and CuAlNi wires combined with H2O2-containing solutions against Enterococcus faecalis, a resilient bacterial species frequently associated with persistent root canal infections. METHODS AND RESULTS: Activity was assessed on planktonic bacteria through CFU counts and on a 2-week-old monospecies biofilm grown on hydroxyapatite discs using SYTO9/propidium iodide staining and fluorescence confocal microscopy. Both Cu-SMAs combined with H2O2 and ascorbic acid (AA) reduced bacterial viability of planktonic cells by 6 log₁₀ after 1-min exposure. In biofilms, CuAlNi/H₂O₂/AA caused cell permeabilization and lysis within 15 min at the wire-biofilm interface. Prolonged exposure led to a time-dependent spatial expansion of bactericidal effects. Diffusing H₂O₂ reacted with Cu²⁺ from the alloy, sustaining a Fenton-like reaction. Gas bubbles formed along the wire generated a convective flow dispersing the reactive mixture millimetres away from the wire surface. CONCLUSIONS: CuAlNi/H₂O₂/AA combination couples radical generation and convection, enabling deep biofilm eradication beyond the wire/solution interface.