title: A study of the efficacy of ultrasonic waves in removing biofilms.
abstract: OBJECTIVE
  The removal of adherent biofilms was assessed using ultrasonic waves in a non-contact mode.
  
  
  METHODS
  In in vitro experiments, Streptococcus mutans (S. mutans) biofilms were exposed to ultrasonic waves at various frequencies (280 kHz, 1 MHz, or 2 MHz), duty ratios (0-90%), and exposure times (1-3 minutes), and the optimal conditions for biofilm removal were identified. Furthermore, the effect of adding a contrast medium, such as micro bubbles (Sonazoid), was examined. The spatial distribution and architecture of S. mutans biofilms before and after ultrasonic wave exposure were examined via scanning electron microscopy. The biofilm removal effect was also examined in in vivo experiments, using a custom-made oral cleaning device.
  
  
  RESULTS
  When a 280 kHz probe was used, the biofilm-removing effect increased significantly compared to 1 and 2 MHz probes; more than 80% of the adherent biofilm was removed with a duty cycle of 50-90% and a 3 minutes exposure time. The maximum biofilm-removing effect was observed with a duty cycle of 80%. Furthermore, the addition of micro bubbles enhanced this biofilm-removing effect. In in vivo experiments, moderate biofilm removal was observed when a 280 kHz probe was used for 5 minutes.
  
  
  CONCLUSIONS
  This study demonstrated that ultrasonic wave exposure in a non-contact mode effectively removed adherent biofilms composed of S. mutans in vitro.
authors.affiliation: Division of Maxillofacial Diagnostic and Surgical Science, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, Kitakyushu, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishikawa
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yoshida
authors.forename: Amit
authors.initials: A
authors.lastname: Khanal
authors.forename: Manabu
authors.initials: M
authors.lastname: Habu
authors.forename: Izumi
authors.initials: I
authors.lastname: Yoshioka
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Toyoshima
authors.forename: Tadamichi
authors.initials: T
authors.lastname: Takehara
authors.forename: Tatsuji
authors.initials: T
authors.lastname: Nishihara
authors.forename: Katsuro
authors.initials: K
authors.lastname: Tachibana
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tominaga
mesh_terms: D001431:Bacteriological Techniques; D018441:Biofilms; D004396:Coloring Agents; D003773:Dental Plaque / Q000382:microbiology / Q000628:therapy; D005290:Ferric Compounds / Q000627:therapeutic use; D006801:Humans; D007501:Iron / Q000627:therapeutic use; D008422:Materials Testing; D045423:Microbubbles / Q000627:therapeutic use; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000627:therapeutic use; D013053:Spectrophotometry; D013295:Streptococcus mutans / Q000502:physiology* / Q000648:ultrastructure; D013997:Time Factors; D014159:Transducers; D014465:Ultrasonics / Q000145:classification
chemical_list: D004396:Coloring Agents; D005290:Ferric Compounds; D010087:Oxides; C069727:Sonazoid; D007501:Iron