Assessment of dentinal fluid flow reduction following simulated brushing with desensitizing toothpastes using sub-nanoliter fluid flow measurement system.

BACKGROUND: This study aimed to quantitatively evaluate dentinal fluid flow reduction following brushing with desensitizing toothpastes using a sub-nanoliter fluid flow measurement system, and to determine the relationship between formulation viscosity and permeability reduction. METHODS: Bovine dentin specimens (n = 10) were subjected to standardized brushing with six toothpaste slurries (Bamboo salt sensitive, Bamboo salt medicare, Colgate, Sensodyne, Median, and Reference slurry) for cumulative counts of 5,000 and 10,000 strokes under simulated pulpal pressure. The percent reduction in dentinal fluid flow (DFF) was calculated relative to baseline and a linear mixed-effects model was used to assess differences in DFF reduction among toothpastes and brushing stages. Toothpaste viscosity was measured using a rheometer and a correlation analysis was conducted to evaluate the association between viscosity and DFF reduction. RESULTS: One desensitizing toothpaste containing stannous fluoride demonstrated a significantly greater reduction in DFF compared with the reference slurry after 5,000 brushing strokes (p < 0.05). No significant additional reduction was observed with continued brushing to 10,000 strokes, and no significant interaction between toothpaste type and brushing stage was identified. A positive association was observed between viscosity measured at 50 s⁻¹ and DFF reduction rate after 5,000 brushings (Spearman ρ = 0.77), although this association did not reach statistical significance. CONCLUSIONS: Desensitizing toothpastes can induce measurable reductions in dentinal fluid flow, with stannous fluoride formulations demonstrating the greatest effect under the present experimental conditions. The majority of tubule occlusion occurred during the initial brushing phase (5,000), with limited additional benefit from continued brushing. Formulation viscosity may contribute to dentinal permeability reduction but does not appear to be the sole determinant of desensitizing efficacy.