Stimuli-responsive piezoelectric orthodontic adhesives for smart biofilm control

Biofilm accumulation on orthodontic appliances hinders oral hygiene, increasing risks of white spot lesions and other oral health issues. Here, we developed a piezoelectric adhesive containing silver-loaded barium titanate (BTO@Ag) nanoparticles that leveraged stimulus responsiveness to achieve controllable and sustained antimicrobial properties. The composite adhesive was synthesized, characterized, and evaluated for safety. An oscillatory device simulating oral movements and an ultrasonic generator mimicking ultrasonic toothbrushes were used to activate the piezoelectric properties of the modified adhesive. Its antimicrobial effects were assessed by evaluating biofilm formation/removal, metabolic activity, and structural integrity of Streptococcus mutans (S. mutans). Results showed that the incorporation of 5 wt% and 10 wt% of BTO@Ag had no significant effect on the adhesive properties and safety of the modified adhesive. It significantly inhibited biofilm formation and metabolic activity under motion-stimulation. Upon ultrasound activation, it further removed residual biofilm and reduced metabolic vitality, with the antimicrobial efficacy exhibiting a dose-dependent enhancement. The antimicrobial activity correlated with increased reactive oxygen species (ROS) production and exhibited sustained efficacy. The developed stimuli-responsive piezoelectric orthodontic adhesive exhibited dynamic antimicrobial activity, presenting a novel strategy for biofilm control during orthodontic treatments.