Influence of Slurry Diluents on Toothpaste Efficacy Against Erosive Tooth Wear: In Vitro and In Situ Studies.

Different diluents are used to prepare toothpaste slurries in vitro and in situ erosive tooth wear studies. This study aimed to evaluate the influence of diluents on the anti-erosive potential of toothpastes with different active agents. Bovine enamel specimens were assigned to groups (n = 12) according to slurry type (in vitro deionized water, in vitro remineralizing solution, clarified human saliva, or in situ human saliva) and toothpaste formulation: placebo (0 ppm F), sodium monofluorophosphate (1450 ppm F - MFP), sodium fluoride (1450 ppm F - NaF), stannous fluoride + sodium fluoride (1100 ppm F SnF₂ + 350 ppm F NaF - NaF/SnF₂), or chitosan (0.5%) + sodium fluoride (700 ppm F) + amine fluoride (700 ppm F) - Chi/NaF/AmF. A 5-day erosion cycle was performed, intercalating four erosive challenges (1 min, 1% citric acid, pH 3.5) and two remineralizing treatments, applied before the first and after the last erosive challenge each day (brushing for 15 seconds and immersion in slurry for up to 2 minutes). Surface microhardness (SMH) and tissue loss by contact profilometry were measured, and percentage SMH loss (%SMH) was calculated. Across all toothpastes, in situ human saliva resulted in the highest SMH and lowest tissue loss. Under in vitro conditions, NaF/SnF₂ and Chi/NaF/AmF slurries with human saliva yielded the best outcomes. For other formulations, no significant differences were observed between in vitro diluents. Results indicate that the diluent type influences SMH and profilometry outcomes, depending on the active agents. Toothpaste containing Sn, chitosan, and fluoride showed the most significant anti-erosive potential.