Ultrasound-activated phase-change nanodroplets for root canal biofilm eradication: mechanistic Investigation and experimental validation

Refractory root canal infections pose a major clinical challenge, as conventional treatments fail to eradicate biofilms in the complex narrow root canal structure. This study proposed a novel strategy of ultrasound-activated phase-change nanodroplets (PCNDs) for biofilm elimination and elucidated its physicochemical and biomechanical mechanisms. A coupled Yang–Church–Pitt (YCP) dynamic model was established to simulate the complete phase transition-cavitation-energy release process of PCNDs under ultrasonic irradiation. Ex vivo experiments on E. faecalis biofilms confirmed that PCNDs efficiently disrupted biofilms via cavitation effects, with efficacy positively correlated with ultrasonic intensity but no significant frequency influence. Minimal temperature of approximately 2 °C rises during treatment verified the strategy’s biosafety, preventing dental hard tissue damage. The YCP model accurately predicted the system’s cavitation characteristics and thermal dynamics, and simulated cavitation energy was strongly correlated with experimental biofilm elimination efficiency. This work validated the safety and efficacy of ultrasound-activated PCNDs for root canal biofilm removal; the YCP model provided a theoretical framework for optimizing ultrasonic parameters, offering a novel mechanistically informed approach for managing refractory root canal infections.