Enamel Surface Finish After Abrasive and Erosive Wear In-Vitro

Both abrasive and erosive wear modify the surface structure of enamel and may alter its appearance. Objectives: Characterise and compare the effects of abrasive and acid erosive wear on surface roughness and gloss of polished human enamel. Methods: Abrasive wear was investigated by brushing flat polished (3µm diamond) enamel specimens (n=8 per treatment) with slurries of Sident silica abrasive grades 8 (low), 9 (med) and 10 (high) in 0.5% carboxymethylcellulose with 10% glycerol, for 10,000 double-strokes using a novel tooth-brushing simulator. Brushing parameters were: 120 strokes/min with Oral-B P35 toothbrushes, brush-head loading of 150g at 20°C. Erosive wear was investigated by immersing identically prepared specimens (n=4) in solutions of 0.3% w/w citric acid monohydrate at 20°C for 5 seconds to 30 minutes with agitation. Before and after treatments, specimens were 2D & 3D profiled on a Taylor-Hobson Talysurf Series 2 profilometer to quantify the surface roughness. Gloss measurements were taken using a Novo-Curve small area gloss meter. Results: The mean ± SD roughness (Ra) values for the 3 abrasive treatments and their respective gloss values ranged from 0.0207±0.0036µm to 0.1102±0.0206µm and 104 to 55 gloss units (GU). For erosive wear the Ra values ranged from 0.0112±0.0004µm to 0.0170±0.0018µm and gloss values from 108 to 55 GU for exposure times 0–10 seconds. Longer treatment times gave rise to much greater changes. Statistically significant differences (p<0.05) were seen for roughness values of both abraded and eroded enamel specimens. Conclusions: Appreciable decreases in gloss were obtained for polished enamel after both abrasive and erosive wear. Reduction in gloss due to abrasive wear was accompanied by appreciable increases in roughness, whereas roughness only increased marginally for similar gloss reductions from erosive wear. These differences between abrasive and erosive wear indicate the need for different strategies for restoration of tooth surface finish.