Methods: Eight bovine enamel specimens per treatment group were prepared to grit 400 / P800 SiC and surface profiled. Specimens were double-brushed sequentially for up to 10,000 strokes in a reciprocal action brushing simulator using a slurry containing 1.0 w/w% calcined alumina abrasive (four preparations with mean particle sizes of 0.05 µm, 3 µm, 9 µm and 20 µm)in carboxymethyl cellulose plus glycerol. Medium filament Oral B toothbrushes were used for the brushing with 150 g load at 20 °C. Gloss measurements were taken before and after brushing with a Novo-Curve small area glossmeter, at intervals of 90 degrees rotation about the centre point of each specimen. After brushing, specimens were surface-profiled for wear depth and surface analysis.
Results: The changes in gloss, wear depth and roughness were not linear in relation to the number of brush strokes. A rank order for mean wear depth of 3>9>20>0.05 μm was observed for the four abrasive preparations with the mean depth of wear for the four abrasives being 1.23, 0.71, 0.70 and 0.22 µm respectively, which paralleled the surface roughness values of 0.102, 0.098, 0.109 and 0.065 µm. Surface gloss analysis revealed values of 90.2, 79.9, 73.4 and 60.9 gloss units for the 0.05, 3, 9 and 20 μm abrasive preparations.
Conclusions: Abrasive particle size can have a marked influence on toothpaste abrasivity and enamel surface polish. Use of abrasive systems with defined particle size profiles offers opportunities to optimize the performance of toothpastes.