In vitro Enamel Wear of Toothpaste Formulations Containing Clay and Charcoal

Objectives: To measure the enamel wear of a silica-based fluoride toothpaste containing clay or clay/charcoal in vitro
Methods: Human enamel blocks were mounted and serially polished to a final 0.3micron alumina powder and surface topography measured with a contact profilometer (SV2000, Mitutoyo). Specimens were masked with PVC tape to leave a 2-3mm window. Test toothpastes (30g) were slurried in water (100ml) and poured over the specimens in a toothbrushing machine. The specimens were brushed for 5,000, 10,000 and 15,000 strokes with a flat trimmed toothbrush, under a load of 175g and speed 2cycles/sec. After each time point, the tape was removed, and the profile of the specimens was remeasured. From the profiles the mean enamel wear was calculated.

The enamel specimens were randomly assigned (n=8) to the test toothpastes which were: Silica toothpaste (A), silica toothpaste + 3%clay (B); silica toothpaste + 3%clay and 0.01%charcoal (C); silica toothpaste + 3%clay and 0.05%charcoal (D), and a prophylaxis paste (E).
Results: The mean (S.D.) enamel wear (microns) after each time point are shown in Table 1 below:


Treatments at same time point with different letters were significantly different (p<0.001, ANOVA).
Conclusions: Incorporation of clay or clay and charcoal into a silica-based toothpaste does not significantly increase enamel wear versus the silica-based toothpaste.