Control of brushing variables for the in vitro assessment of toothpaste abrasivity using a novel laboratory model.
OBJECTIVE
Design and construct a tooth-brushing simulator incorporating control of brushing variables including brushing force, speed and temperature, thereby facilitating greater understanding of their importance in toothpaste abrasion testing methodologies.


METHODS
A thermostable orbital shaker was selected as a base unit and 16- and 24-specimen brushing rigs were constructed to fit inside, consisting of: a square bath partitioned horizontally to provide brushing channels, specimen holders for 25 mm diameter mounted specimens to fit the brushing channels and individually weighted brushing arms, able to support four toothbrush holders suspended over the brushing channels. Brush head holders consisted of individually weighted blocks of Delrin, or PTFE onto which toothbrush heads were fixed. Investigating effects of key design criteria involved measuring abrasion depths of polished human enamel and dentine.


RESULTS
The brushing simulator demonstrated good reproducibility of abrasion on enamel and dentine across consecutive brushing procedures. Varying brushing parameters had a significant impact on wear results: increased brushing force demonstrated a trend towards increased wear, with increased reproducibility for greater abrasion levels, highlighting the importance of achieving sufficient wear to optimise accuracy; increasing brushing temperature demonstrated increased enamel abrasion for silica and calcium carbonate systems, which may be related to slurry viscosities and particle suspension; varying brushing speed showed a small effect on abrasion of enamel at lower brushing speed, which may indicate the importance of maintenance of the abrasive in suspension.


CONCLUSIONS
Adjusting key brushing variables significantly affected wear behaviour. The brushing simulator design provides a valuable model system for in vitro assessment of toothpaste abrasivity and the influence of variables in a controlled manner. Control of these variables will allow more reproducible study of in vitro tooth wear processes.
Parry
Jason
J
The School of Dentistry, University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, UK. j.parry.1@bham.ac.uk <j.parry.1@bham.ac.uk>
Harrington
Edward
E
Rees
Gareth D
GD
McNab
Rod
R
Smith
Anthony J
AJ
D002119:Calcium Carbonate / Q000009:adverse effects / Q000737:chemistry; D002131:Calcium Pyrophosphate / Q000009:adverse effects / Q000737:chemistry; D003743:Dental Enamel / Q000473:pathology; D003804:Dentin / Q000473:pathology; D004867:Equipment Design; D006801:Humans; D010316:Particle Size; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000009:adverse effects / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014072:Tooth Abrasion / Q000209:etiology* / Q000473:pathology; D014099:Toothbrushing / Q000295:instrumentation / Q000379:methods*; D014100:Toothpastes / Q000009:adverse effects* / Q000737:chemistry; D014783:Viscosity
D014100:Toothpastes; D012822:Silicon Dioxide; D002119:Calcium Carbonate; D002131:Calcium Pyrophosphate