No abstract

Under the conditions of this short-term in vitro experiment, it could be concluded that increasing the viscosity of the oral rinse solutions reduced enamel loss by erosion; however, this effect was small and only observed when the solutions were applied once a day.

Objectives To investigate the effect of toothpastes on dentine surface loss and tubule occlusion, and the association of toothpasterelated factors to each of the outcomes. Materials and methods One hundred and sixty human dentine specimens were randomly distributed into 10 groups, according to different toothpastes. The specimens were submitted to artificial saliva (60 min), citric acid (3 min), and brushing abrasion (25 s; totalizing 2 min in toothpaste slurries). This was repeated five times and two outcome variables were analyzed: dentine surface loss (dSL; μm) and tubule occlusion by measurement of the total area of open tubules (Area-OT; μm 2 ). Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α = 0.05); bivariate and multivariate regressions were used to model the association of the chemical (pH, concentration of F − , Ca 2+ , and PO 4 3− and presence of Sn 2+ ) and physical (% weight of solid particles, particle size, and wettability) factors of the toothpastes to both outcome variables. Results Toothpastes caused different degrees of dSL and did not differ in Area-OT. All chemical and physical factors, except the presence of Sn 2+ , were associated with dSL (p < 0.001). Area-OT was associated only with the presence of Sn 2+ (p = 0.033). Conclusion Greater dSL was associated with lower pH, lower concentration of F − , higher concentration of Ca 2+ and PO 4 3− , greater % weight of solid particles, smaller particle size, and lesser wettability, whereas tubule occlusion was associated with the presence of Sn 2+ . Clinical relevance Depending on their chemical and physical composition, toothpastes will cause different degrees of dentine tubule occlusion and dentine surface loss. This could, in turn, modulate dentine hypersensitivity.

The aim of this study was to evaluate the protective effect of propylene glycol alginate (PGA) associated with sodium fluoride (NaF) against enamel erosion and erosion-abrasion. A 4-phase, split-mouth, double-blind, crossover in situ trial was conducted with the following solutions: F + PGA (225 ppm F^– + 0.1% PGA), F (225 ppm F^–), F + Sn (225 ppm F^– + SnCl₂, 800 ppm Sn²⁺), and negative control (distilled water). In each phase, 12 subjects wore removable mandibular appliances containing 4 enamel specimens, which were submitted either to erosion or to erosion-abrasion challenges for 5 days. Acquired salivary pellicle was formed in situ for 2 h. Erosion-abrasion consisted of acid challenge (1% citric acid solution, pH 2.3, 5 min, 4×/day), exposure to saliva in situ (2 h, 4×/day), brushing (5 s, total 2 min exposure to the slurry), and treatment with the solutions (2 min, 2×/day). For erosion, the same procedures were performed, without brushing. At the end, surface loss (SL; in μm) was evaluated by means of optical profilometry. KOH-soluble fluoride was quantified for erosion-only groups using extra specimens. For both challenges, the SL values found for F + PGA did not differ significantly from those of F and the negative control, and the SL value shown for F + Sn was significantly the lowest. Erosion-abrasion promoted significantly higher SL values than erosion. KOH-soluble fluoride analysis showed that F + Sn had a higher fluoride concentration in comparison with the negative control and F, while F + PGA did not differ from any of the other groups. In conclusion, PGA was not able to improve the protective effect of NaF against erosive enamel wear.