Polishing Effect of Standard Abrasive Silicas on Roughened Enamel in-vitro

The relationship between tooth surface gloss and roughness may be important for oral aesthetics and modulation of toothpaste abrasivity could contribute to this. Objectives: Investigate the influence of three grades of abrasive silica on in-vitro wear profiles and surface finish of pre-roughened human enamel, using a novel brushing simulator. Methods: Low, medium and high abrasivity silicas were investigated by brushing flat ground (800 grit SiC) human enamel specimens. Specimens (n=8 per treatment) were brushed 10,000 double-strokes with slurries of Sident grades 8 (low), 9 (med) and 10 (high) in 0.5% Hercules 7MF carboxymethylcellulose with 10% glycerol. Brushing was performed using a modified Jeiotech SI300R reciprocating incubator shaker containing a tooth brushing rig, into which sixteen 25mm diameter mounted samples could be positioned. The brushing simulator allowed the control of brushing parameters, which were; 120 strokes/min with Oral-B P35 indicator toothbrushes, brush head loading of 150g and a temperature of 20°C. Before and after brushing, specimens were 2D & 3D profiled on a Taylor-Hobson Talysurf Series 2 profilometer to quantify the abrasion and surface roughness. Gloss measurements were also taken before and after brushing using a Novo-Curve small area gloss meter. Results: The mean ± standard deviation values for roughness Ra and Gloss of specimens before and after brushing were: As ground: Ra 0.2461±0.0345µm, Gloss 12.5±5.2; Sident 8: Ra 0.1200±0.0259µm, Gloss 70.2±11.7; Sident 9: Ra 0.1668±0.0220µm, Gloss 52.9±8.4; Sident 10: Ra 0.1850±0.0180µm, Gloss 45.5±9.6. The values of roughness and gloss obtained from specimens brushed with the three silicas were significantly different statistically (p<0.05). Conclusions: There was an appreciable decrease in the roughness, coupled with a significant increase in gloss after brushing flat ground enamel using slurries of abrasive silicas. The least abrasive silica produced the best surface finish, in terms of gloss and roughness.