A study of the efficacy of ultrasonic waves in removing biofilms.
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.
Nishikawa
Takeshi
T
Division of Maxillofacial Diagnostic and Surgical Science, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, Kitakyushu, Japan.
Yoshida
Akihiro
A
Khanal
Amit
A
Habu
Manabu
M
Yoshioka
Izumi
I
Toyoshima
Kuniaki
K
Takehara
Tadamichi
T
Nishihara
Tatsuji
T
Tachibana
Katsuro
K
Tominaga
Kazuhiro
K
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
D004396:Coloring Agents; D005290:Ferric Compounds; D010087:Oxides; C069727:Sonazoid; D007501:Iron