Low temperature atmospheric pressure plasma applications in dentistry: Two independent studies

Abstract

Low temperature atmospheric pressure plasma (LTAPP) may be used for various biomedical applications as this technology has the potential to inactivate and destroy microorganisms1,2. Purpose: The purpose of these two independent studies was to evaluate the efficacy of LTAPP on the inactivation of Geobacillus stearothermophilus, Bacillus cereus and Streptococcus mutans. The microorganisms of the study are of dental relevance. Methods: In Study 1, 981 samples were processed (762 experimental samples exposed to LTAPP, 219 control samples). Experimental samples of G. stearothermophilus and B. cereus (vegetative cells and spores) were exposed indirectly or directly to cold plasma at various time intervals for each microorganism state and type of exposure (indirect exposure time range: 1 minute-30 minutes; direct exposure time range: 30 seconds-30 minutes). In study 2, 90 samples were processed (72 experimental samples exposed to LTAPP, 18 control samples). Experimental samples of S. mutans were exposed directly to cold plasma for 60, 120, 180 or 300 seconds. In both studies: control samples were not exposed, colony forming units were counted, percentage kill/ inactivation factor were determined and data were analyzed at 0.05a significance. Analysis for study 1 included one-way ANOVA, Kruskal Wallis and Tukey's tests and study 2 used repeated measures ANOVA. Results: Study 1: Statistically significant reduction of G steraothermophilus vegetative cells and B. cereus vegetative cells and spores (indirect and direct exposure p-values O.025). There was no statistically significant reduction for G stearothermophilus spores (indirect p=3D0.7208, direct p=3D0.0835). Study 2: Statistically significant reduction of S. mutans at all time exposures: 60 (p=3D0.0272), 120, 180 and 300 seconds (p=3D0.0001). Conclusions: Results demonstrate that LTAPP effectively kills G stearothermophilus vegetative cells, B. cereus vegetative cells and spores and S. mutans. G stearothermophilus spores were not significantly inactivated.