Influence of Abrasive Particle Size on Surface Finish of Enamel

Objectives: Inclusion of abrasive particles in toothpastes can impact on both dental tissue wear and surface finish of the tissue, although generally use of abrasives with broad particle ranges precludes an understanding of the influence of particle size. The objective of this study was to investigate the effect of abrasive particle size on the wear and surface finish of polished enamel. Methods: Eight bovine enamel specimens per treatment group were prepared to 1200-grit SiC and 3 µm diamond finishes and surface profiled. Specimens were double-brushed for 10,000 strokes in a reciprocal action brushing simulator using a slurry containing 1.0 w/w% alumina abrasive (four preparations with mean particle sizes of 0.05 µm, 3 µm, 9 µm and 20 µm) in Carboxymethyl Cellulose plus Glycerol. A soft filament Sensodyne Dr Best toothbrush was used for the brushing at 150 g load at 20 °C. The brushes were modified by excision of the front group and all but one of the rows of tufts to provide a linear tuft arrangement avoiding brush tuft arrangement as a variable. After brushing, specimens were surface-profiled for wear depth and surface analysis. Results: A rank order for wear of 3>9>20>0.05 ìm was observed for the four abrasive preparations with the mean depth of wear for the four abrasives being 0.76, 0.47, 0.23 and 0.14 µm respectively, which paralleled the surface roughness values of 0.147, 0.127, 0.063 and 0.033 µm. Surface gloss analysis revealed values of 99.3, 71.2, 57.4 and 70.2 gloss units for the 0.05, 3, 9 and 20 ìm abrasive preparations. Conclusions: Abrasive particle size can have a marked influence on toothpaste abrasivity and enamel surface finish. Use of abrasive systems with defined particle size profiles offers opportunities to optimize the performance of toothpastes.