title: Plasma deactivation of oral bacteria seeded on hydroxyapatite disks as tooth enamel analogue.
abstract: OBJECTIVE
  To study the plasma treatment effects on deactivation of oral bacteria seeded on a tooth enamel analogue.
  
  
  METHODS
  A non-thermal atmospheric pressure argon plasma brush was used to treat two different Gram-positive oral bacteria including Lactobacillus acidophilus (L. acidophilus) and Streptococcus mutans (S. mutans). The bacteria were seeded on hydroxyapatite (HA) disks used as tooth enamel analogue with three initial bacterial seeding concentrations: a low inoculum concentration between 2.1 x 10(8) and 2.4 x 10(8) cfu/mL, a medium inoculum concentration between 9.8x10(8) and 2.4 x 10(9) cfu/mL, and a high inoculum concentration between 1.7 x 10(10) and 3.5 x 10(10) cfu/mL. The bacterial survivability upon plasma exposure was examined in terms of plasma exposure time and oxygen addition into the plasmas. SEM was performed to examine bacterial morphological changes after plasma exposure.
  
  
  RESULTS
  The experimental data indicated that a 13-second plasma exposure time completely killed all the bacteria when initial bacterial seeding density on HA surfaces was less than 6.9 x 10(6) cfu/cm2 for L. acidophilus and 1.7 x 10(7) cfu/cm2 for S. mutans, which resulted from low initial seeding inoculum concentration between 2.1 x 10(8) and 2.4 x 10(8) cfu/mL. Plasma exposure of the bacteria at higher initial bacterial seeding density obtained with high initial seeding inoculum concentration, however, only resulted in approximately 1.5 to 2 log reduction and approximately 2 to 2.5 log reduction for L. acidophilus and S. mutans, respectively. It was also noted that oxygen addition into the argon plasma brush did not affect the plasma deactivation effectiveness. SEM images showed that plasma deactivation mainly occurred with the top layer bacteria, while shadowing effects from the resulting bacterial debris reduced the plasma deactivation of the underlying bacteria.
authors.forename: Adam
authors.initials: A
authors.lastname: Blumhagen
authors.forename: Prashant
authors.initials: P
authors.lastname: Singh
authors.forename: Azlin
authors.initials: A
authors.lastname: Mustapha
authors.forename: Meng
authors.initials: M
authors.lastname: Chen
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Yu
mesh_terms: D058491:Bacterial Load / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects; D003743:Dental Enamel / Q000382:microbiology*; D017886:Durapatite / Q000737:chemistry*; D006801:Humans; D007779:Lactobacillus acidophilus / Q000187:drug effects*; D050296:Microbial Viability / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D010100:Oxygen / Q000494:pharmacology; D010126:Ozone / Q000494:pharmacology; D058626:Plasma Gases / Q000627:therapeutic use*; D013295:Streptococcus mutans / Q000187:drug effects*; D013997:Time Factors
chemical_list: D058626:Plasma Gases; D010126:Ozone; D017886:Durapatite; D010100:Oxygen