Drug-Silica Co-Assembled Particles Improve Antimicrobial Properties of Endodontic Sealers

Objectives: To assess the antimicrobial and flow of root canal sealers after incorporating a novel highly-loaded antimicrobial drug-silica co-assembled particles (DSPs).
Methods: DSPs were synthesized through co-assembly of silica and Octenidine dihydrochloride (OCT) surfactant drug, forming highly loaded (35%wt) OCT-silica nanocomposite microspheres. DSPs (1 and 2%W/W) were loaded into epoxy resin sealer (AH, AH Plus®, Dentsply) or silicate-based sealer (BC Sealer^TM ,EndoSequence). OCT release from the DSPs-modified sealers were determined using Ultra Performance Liquid Chromatography, OCT minimum inhibitory concentration (MIC) and antimicrobial activity of sealers against planktonic or biofilms of Enterococcus Faecalis using modified direct contact test or direct contact and membrane restricted tests, respectively. Flow of sealers was tested using ISO 6876, 2012.
Results: MIC of OCT against E. faecalis is 4 µg/mL. AH release of OCT was below MIC (~0.05 µg/mL) while BC sealer had a higher release of with a peak of (~9-10 µg/mL). All materials (with or without DSPs) showed initial complete killing of bacteria compared to control (no sealer) group. Non-DSP containing BC and AH with or without DSPs had no antimicrobial activity after 7 day. In contrast, BC with 1% and 2% DSPs were able to maintain the antibacterial activity over the 30 days. DSPs decreased the flow of AH and BC sealers; the reduction was proportional to the amount of DSPs added (21.7, 17.8 and 15.7mm for AH+1% and 2% DSP respectively; 24.9, 21.8 and 19.7mm for BC+1% and 2% respectively), All modified and unmodified sealers were within the acceptable limitations of ISO flow limit (17mm) except for AH+2% DSPs.
Conclusions: DSPs improved the antimicrobial performance of BC but not AH sealer while maintaining the BC flow compliant with the ISO standard. Depending on the sealer, DSPs could potentially prevent interfacial biofilm formation and proliferation, improving treatment outcome.