Synergistic effect of microbubble emulsion and sonic or ultrasonic agitation on endodontic biofilm in vitro

This study examined the effects of a microbubble emulsion (ME) combined with sonic or ultrasonic agitation, on irrigation dynamics and reduction of biofilm bacteria. High-speed imaging was used to characterize the bubble dynamics generated in ME by sonic or ultrasonic agitation within polymer teeth. 5.25% NaOCl or ME was sonically or ultrasonically agitated in canals of extracted teeth with 7-day-old Enterococcus faecalis biofilms. Dentinal shavings were sampled and colony-forming units (CFU) enumerated. Mean log CFU/ml values were analyzed with ANOVA and post-hoc tests. Strongly oscillating and vaporizing bubbles were generated within ME during ultrasonic, but not sonic agitation. Post-treatment biofilm CFU were significantly lower in the ultrasonic agitation (P=0.000) of ME group than in the ultrasonic (P=0.009) and sonic agitation ( P=0.006) of NaOCl groups. The synergistic effect of ME combined with ultrasonic agitation enhanced bubble dynamics and reduced E. faecalis biofilm bacteria beyond the level achieved by agitation of NaOCl.