Oregano Nanoemulsion Antibacterial Effects In Enterococcus Faecalis Root Canals

This study develops a nanoemulsified oregano oil formulation to suppress persistent Enterococcus faecalis biofilms in root canals, addressing antimicrobial resistance challenges in endodontic disinfection. Steam-distilled oregano oil was analyzed by GC-MS (49 compounds identified, carvacrol [21.94%] and thymol [15.87%] as major components). Optimized nanoemulsions were developed through single-factor screening and Box-Behnken response surface methodology (TW-80 surfactant, ethanol cosurfactant, Km=3.01, Smix/O=4.2, 8% oil content). Antibiofilm efficacy was evaluated against clinical standards (NaOCl, CHX) using agar diffusion, colony counting, SEM, and CLSM on extracted teeth. The nanoemulsion showed comparable biofilm inhibition to 1% NaOCl (P>0.05), surpassing 0.12% CHX, gentamicin, and pure oregano oil (P<0.05). SEM/CLSM confirmed significant disruption of biofilm architecture in dentinal tubules, with bacterial viability reduction levels between 1-2% NaOCl. Colony counts revealed efficacy hierarchy: 2% NaOCl >1% NaOCl >nanoemulsion >0.12% CHX >pure oil >gentamicin >saline. Engineered oregano oil nanoemulsion demonstrates potent biofilm inhibition comparable to 1% NaOCl while overcoming volatility and solubility limitations of crude extracts. This natural strategy provides a promising alternative for resistant endodontic infections, particularly in sodium hypochlorite-sensitive clinical applications.