Assunçao CM, et al. - Researchers randomly divided 17 enamel samples according to toothpaste groups as G1: placebo; G2: NaF; G3: AmF-NaF-SnCl2 anti-erosion; G4: SnF2; and G5: NaF anti-erosion to assess the preventive effect of different kinds of toothpaste on surface loss (SL) after severe erosion/abrasion model and to compare this effectiveness between permanent (PT) and primary teeth (pt). They incubated the samples in artificial saliva (1 hour), submitted to erosive challenge (3 minutes; 1% citric acid; pH3.6; at 25°C) and to toothbrush abrasion (2 minutes slurry immersion; 50 strokes; 200 g) during 30 cycles and the effects were examined by Wilcoxon tests. They observed that G3 showed the best preventive effect in permanent teeth but a higher incidence of SL in pt.