Enamel Surface Finish after Brushing with Micronised Silicas in vitro

Objectives: To determine whether brushing with a micronised amorphous precipitated abrasive silica grade (MS) can provide superior enamel surface finish relative to brushing with a conventional non-micronised silica grade (CS).  Methods: Flat ground (800 grit) enamel specimens (n=8 per treatment) were brushed with slurries of CS (typical particle size distribution: d50=9.0μm; d90=30.6μm) or MS (typical particle size distribution: d50=3.4μm; d90=6.3μm), at 16.7% w/w silica in 0.5% w/w carboxymethylcellulose with 10% w/w glycerol.  Brushing conditions were: 120 strokes/min for 10,000 double-strokes at 20°C, using a novel tooth-brushing simulator at 150g loading.  This protocol was repeated using 1+3 w/w aqueous slurries of dentifrices containing 14% w/w CS with and without 4.2% w/w MS.  Enamel surface roughness (Ra) was assessed before and after treatment (perpendicular to brush direction) using a Taylor-Hobson Talysurf Series 2 profilometer.  Enamel surface gloss was assessed in gloss units (GU) before and after treatment with pastes using a Novo-Curve Small Area Glossmeter. Results: The data are summarised below: