The effect of magnesium hydroxide-containing dentifrice using an extrinsic and intrinsic erosion cycling model

Abstract

ObjectiveTo evaluate, in vitro, the effect of Mg(OH)2 dentifrice, and the influence of the number of experimental days, on the extrinsic (citric acid –CA) and intrinsic (hydrochloric acid –HCl) enamel erosion models. DesignHuman enamel slabs were selected according to surface hardness and randomly assigned to 3 groups (n=9) as follows: non-fluoridated (negative control), NaF (1450ppm F- positive control) and Mg(OH)2 (2%) dentifrices. The slabs were daily submitted to a 2-h period of pellicle formation and, over a period of 5days, submitted to cycles (3×/day) of erosive challenge (CA 0.05M, pH=3.75 or HCl 0.01M, pH=2 for 30s), treatment (1min −1:3w/w of dentifrice/distilled water) and remineralization (artificial saliva/120min). Enamel changes were determined by surface hardness loss (SHL) for each day and mechanical profilometry analysis. Data were analyzed by two-way ANOVA followed by Tukey’s test to % SHL and one-way ANOVA to profilometry (p<0.05). ResultsThe number of experimental days influenced the erosion process for the two types of erosion models (p<0.001). Mg(OH)2-containing dentifrices were effective in reducing enamel extrinsic acid erosion as determined by % SHL (p<0.001) when compared to the control group, being better than positive control (p<0.001); however, the dentifrices were not effective for the intrinsic model (p=0.295). With regards to surface wear, no statistically significant differences were found among the groups for CA (p=0.225) and HCl (p=0.526). ConclusionThe findings suggest that Mg(OH)2 dentifrices might protect enamel against slight erosion, but protection was not effective for stronger acid erosion.