Acid origin modulates the protective effect of an experimental anti-erosive gel against enamel erosion

OBJECTIVES: To evaluate the effect of experimental fluoride gels containing the bioadhesive polymer Carbopol 980, alone or combined with stannous ions, on enamel mineral release and to determine whether their protective effects differ according to the origin of the erosive acid. METHODS: + 2 g/100mL, pH 5.5) gels. Mineral release was quantified by calcium and phosphate release throughout the erosive cycling. Surface morphology and elemental composition were qualitatively evaluated by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Data were analyzed using Kruskal-Wallis and Dwass-Steel-Critchlow-Fligner tests (α=0.05). RESULTS: Before treatment, citric acid produced greater calcium (p=0.003) and phosphate (p < 0.001) release than hydrochloric acid. After treatment, significant differences among gels were observed for calcium loss (p < 0.001). During the 5-day cycling, treatment effects were detected only under citric acid challenge, where NaF + C980 and NaF + Sn + C980 significantly reduced calcium and phosphate loss compared with C980 alone and performed similarly to APF. Under hydrochloric acid challenge, no significant differences were found among treatments. SEM and EDS supported these findings by revealing protective surface deposits and the presence of fluoride and tin on treated enamel. CONCLUSIONS: Experimental fluoride-containing gels, with or without stannous ions, reduced enamel mineral release compared with the Carbopol 980 placebo under the citric acid challenge. However, this protective effect was not observed under hydrochloric acid, indicating that the effect of the formulations on mineral release depended on the erosive acid used. The findings highlight the importance of considering the type of erosive acid used when evaluating and comparing anti-erosive formulations. CLINICAL SIGNIFICANCE: Acid chemistry influences the protective effect of professional anti-erosive formulations and should be considered when developing preventive strategies for erosive tooth wear.