title: Energy transfer, volumetric expansion, and removal of oral biofilms by non-contact brushing.
abstract: Non-contact removal of oral biofilms offers advantages beyond the reach of bristles, but it is unknown how energy transfer for removal from brush-to-biofilm occurs. In the present study we evaluated non-contact, oral biofilm removal by oscillating-rotating and sonic toothbrushes, and their acoustic output up to 6 mm distance. Whereas some brushes removed biofilm when used at a distance of up to 6 mm, others lost efficacy at a distance of 2-4 mm from the biofilm. Loss of efficacy was accompanied with high standard deviations and volumetric biofilm expansion. Both sonic and oscillating-rotating brushes caused fluid flows and the inclusion of air-bubbles, while non-contact acoustic energy-transfer was demonstrated to decay with distance for both types of brushes. We put forward the following mechanism for non-contact removal: (i) brush energy is absorbed by biofilm, resulting in the visco-elastic expansion of the biofilm; (ii) if the energy absorbed is sufficient and deformation is beyond the yield point, biofilm removal occurs; and (iii) if deformation is in the plastic range but below the yield point (i.e. at the limiting distance for non-contact removal), biofilm is expanded but not removed.
authors.affiliation: Department of Biomedical Engineering, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
authors.forename: H J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: D
authors.initials: D
authors.lastname: Jager
authors.forename: G
authors.initials: G
authors.lastname: Finger
authors.forename: N
authors.initials: N
authors.lastname: Schaefer
authors.forename: H C
authors.initials: HC
authors.lastname: van der Mei
mesh_terms: D000042:Absorption; D000162:Acoustics; D000190:Actinomyces / Q000502:physiology*; D001422:Bacterial Adhesion; D018441:Biofilms; D001696:Biomechanical Phenomena; D044622:Dental Pellicle / Q000382:microbiology; D055119:Elastic Modulus; D004735:Energy Transfer; D004867:Equipment Design; D006801:Humans; D018613:Microscopy, Confocal; D012212:Rheology; D012399:Rotation; D012463:Saliva / Q000382:microbiology; D019533:Streptococcus oralis / Q000502:physiology*; D014099:Toothbrushing / Q000295:instrumentation / Q000379:methods*; D014783:Viscosity