A Sub-microsecond Pulsed Plasma Jet for Endodontic Biofilm Disinfection
A pulsed, tapered cylindrical plasma jet, several centimeter long and <2 mm in diameter, has been generated by a concentric tubular device for root canal disinfection. This plasma dental probe is typically powered with ∼100 ns, 1 kHz, multi-kilovolt electric pulses and filled with 5 SLPM (standard liter per minute) He/(1%)O2 flow. We report here an in vitro study of the antimicrobial effect of the room temperature plasma jet against monolayer Enterococcus faecalis biofilms on bovine dentins. Resultant colony-forming unit counts were associated with changes in bacterial cell morphology observed using scanning electron microscopy (SEM) following the treatment and control. Treatment of dentin discs cultivated with E. faecalis monolayer biofilms with the plasma (average power ≈ 1 W) for 5 min resulted in 92.4% kill (P < 0.0001). Severe disruption of the cell membranes was observed for the plasma treatment group, while the morphology of the cells remained intact for the negative control group. In addition, a pilot ex vivo test was conducted to examine the bactericidal effect of the plasma against saliva-derived biofilms cultivated in human root canals. Conspicuous biofilm disruption and cleared dentinal surfaces were observed in the canal after the plasma treatment for 5 min. We conclude that this non-thermal pulsed plasma-based technology is a potential alternative or supplement to existing protocols for root canal disinfection.
KeywordsPlasma Treatment Root Canal Plasma Plume Smear Layer Dentinal Surface
The authors thank Dr. Shawn Anderson for the donation of the tooth specimens for the experiments. This work is supported by the National Institute of Dental and Craniofacial Research (NIDCR), one of the National Institutes of Health (NIH) in the U.S. Department of Health and Human Services.
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