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Interactions between toothbrush and toothpaste particles during simulated abrasive cleaning

Lewis, R. and Dwyer-Joyce, R.S. (2006) Interactions between toothbrush and toothpaste particles during simulated abrasive cleaning. Proceedings of the Institution of Mechanical Engineers. Part J: Journal of engineering tribology, 220 (8). pp. 755-765. ISSN 1350-6501

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Most people clean their teeth using toothpaste, consisting of abrasive particles in a carrier fluid, and a filament based toothbrush to remove plaque and stain. In order to optimise cleaning efficiency it is important to understand how toothbrush filaments, abrasive particles and fluid interact in a tooth cleaning contact.

Work has been carried out to visualise, simulate, and model the processes in teeth cleaning. Laboratory cleaning contacts were created between a toothbrush and a transparent surface. Video and short duration flash photography were used to study the processes by which a toothbrush traps abrasive particles, loads them against the counterface, and removes material. Small abrasive particles tend to be trapped at the contact between the filament tip and the counterface, whilst larger particles are trapped by clumps of filaments or at the contact with the side of a bent filament.

Measurements of brush friction force were recorded during cleaning for a range of operating conditions. The presence of abrasive particles in the cleaning mixture increased the coefficient of friction, but the absolute particle concentration showed a lesser effect. It is surmised that only a few particles carry any load and cause any abrasion; increasing the particle concentration does not directly increase the number of load bearing particles. Abrasive scratch tests were also carried out, using PMMA as a wearing substrate. The scratches produced during these tests were studied. The microscopy images were used to deduce how the filaments deflect and drag, and how particles are trapped by filaments and scratch the surface. Again, it was observed that few of the brush filaments loaded particles to produce scratches, and that when a filament changes direction of travel the trapped particle is lost.

Results of these studies were used to develop both qualitative and quantitative models of the process by which material is removed in teeth cleaning. The quantitative model contains, by necessity, several empirical factors, but nonetheless predictions compare well with in vitro wear results from the literature. The results were also used to draw some broad conclusions on appropriate brushing techniques for optimum tooth cleaning.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright © 2006 Professional Engineering Publishing. This is an author produced version of a paper subsequently published in Proceedings of the Institution of Mechanical Engineers. Part J. This paper has been peer-reviewed but may not include the final publisher proof-corrections or journal pagination.
Keywords: teeth cleaning, abrasive particles, toothbrush, toothpaste
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield)
Depositing User: Repository Officer
Date Deposited: 13 Feb 2007
Last Modified: 05 Jun 2014 12:19
Published Version: http://dx.doi.org/10.1243/13506501JET96
Status: Published
Publisher: Professional Engineering Publishing
Refereed: Yes
Identification Number: 10.1243/13506501JET96
URI: http://eprints.whiterose.ac.uk/id/eprint/1964

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