OBJECTIVE: To study the plasma treatment effects on deactivation effectiveness of oral bacteria. METHODS: A low temperature atmospheric argon plasma brush were used to study the oral bacterial deactivation effects in terms of plasma conditions, plasma exposure time, and bacterial supporting media. Oral bacteria of Streptococcus mutans and Lactobacillus acidophilus with an initial bacterial population density between 1.0x10(8) and 5.0x10(8)cfu/ml were seeded on various media and their survivability with plasma exposure was examined. Scanning electron microscopy was used to examine the morphological changes of the plasma treated bacteria. Optical absorption was used to determine the leakage of intracellular proteins and DNAs of the plasma treated bacteria. RESULTS: The experimental data indicated that the argon atmospheric plasma brush was very effective in deactivating oral bacteria. The plasma exposure time for a 99.9999% cell reduction was less than 15s for S. mutans and within 5 min for L. acidophilus. It was found that the plasma deactivation efficiency was also dependent on the bacterial supporting media. With plasma exposure, significant damages to bacterial cell structures were observed with both bacterium species. Leakage of intracellular proteins and DNAs after plasma exposure was observed through monitoring the absorbance peaks at wavelengths of 280 nm and 260 nm, respectively. CONCLUSION: The experimental results from this study indicated that low temperature atmospheric plasma treatment was very effective in deactivation of oral bacteria and could be a promising technique in various dental clinical applications such as bacterial disinfection and caries early prevention.
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