Magnesium Hydroxide-containing Dentifrice on Enamel Erosion Models

Objectives: To evaluate, in vitro, the effect of MgOH₂ dentifrice, and the influence of the number of experimental days, on the extrinsic (citric acid - C₆H₈O₇) and intrinsic (hydrochloric acid -HCl) enamel erosion models.
Methods: Human enamel slabs were selected according to surface hardness and randomly assigned to 3 groups (n=9) as follows: non-fluoridated (control), NaF (1,450 ppm F) and MgOH₂ (2%) dentifrices. The slabs were daily submitted to a 2-hour period of pellicle formation and, over a period of 5 days, submitted to cycles (3x/day) of erosive challenge (C₆H₈O₇ 0.05 M, pH 3.75 or HCl 0.01 M, pH=2 for 30 s), treatment (1 min -1:3 w/w of dentifrice/distilled water) and remineralization (artificial saliva/120 min). 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).
Results: The number of experimental days influenced the erosion process for the two types of erosion models (p<0.001). The NaF and MgOH₂-containing dentifrices were effective in reducing enamel extrinsic acid erosion as determined by %SHL (p<0.001) when compared to the control group; 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 citric acid (p=0.225) and hydrochloric acid (p=0.526).
Conclusions: : The findings suggest that NaF and MgOH₂ dentifrices might protect enamel against slight erosion, but protection was not effective for stronger acid erosion.