Desensitizing toothpastes with low pH to prevent erosion and abrasion

Objectives: The aim of this study was to investigate the protective effect of experimental toothpastes, containing desensitizing agents and/or fluoride, with acidic pH, on erosion (ERO) associated or not with abrasion (ERO+ABR) of bovine enamel.

Methods: The groups were separated regarding the active compound present in the toothpaste: toothpaste containing desensitizing agent, fluoride toothpaste (1100 ppm F, as NaF) or both combined The tested desensitizing agents were: strontium cloride (10% SrCl₂), potassium citrate (5% KCit) and potassium nitrate (5% KNO₃). Each toothpaste was formulated in neutral (7.0) or acidic pH (4.5). Placebo toothpaste without desensitizing agents and fluoride was tested as negative control (pH 7.0). The enamel blocks were divided into 15 groups for each condition to be tested (ERO and ERO+ABR) by surface microhardess (n=20/group) and submitted to four de-remineralization cycles in only one day. Demineralization was provoked by a cola soft drink (5 min) and remineralization in artificial saliva (55 min). Between the pH-cycles, the blocks were brushed, using an automatic machine and slurry of tested toothpaste (3 g toothpaste/10 mL water), during 30 s (ERO+ABR). For ERO, the blocks were immersed in the slurry for 1 min. Erosive tissue loss was analyzed by profilometry (µm). Data were tested by t test, one-way ANOVA, three-way ANOVA and Tukey’s test (p<0.05).

Results: All groups were significantly different from placebo, except for theKNO₃+F group, pH 7.0 (ERO+ABR). Toothpastes with acidic pH led to significantly lower enamel loss when compared with the neutral ones, for both conditions. Fluoride reduced enamel loss when combined with desensitizing agents, except for KNO₃.

Conclusions:  These in vitro results suggest that the presence of fluoride and desensitizing substances in toothpastes, alone or in combination, as well as the acidic pH can reduce enamel erosion alone or combined with abrasion.