Nano-sized TMP enhances the anticaries effects of a low-fluoride toothpaste in situ

Objectives: To assess the effects of a low-fluoride toothpaste containing nano-sized sodium trimetaphosphate (TMPnano) on enamel demineralization, as well as on the composition of dental biofilm formed in situ.
Methods: Volunteers (n=19) were randomly assigned into 4 experimental groups, following a double-blind, crossover protocol, according to the following toothpastes: Placebo (without F/TMP), 250 ppm F (250F), 250F plus 0.05% TMPnano (250 TMPnano) and 1,100 ppm F (1100F). Volunteers wore palatal appliances containing 4 blocks of bovine enamel, which were subjected to cariogenic challenges (30% sucrose solution) 6 times/day, and to treatment with slurries of the same toothpastes twice/day, during 7 days. Specimens were analyzed by surface (SH) and cross-sectional (ΔKHN) hardness, as well as for fluoride (F), calcium (Ca), and phosphorus (P) concentrations. The biofilm formed on the specimens were analyzed for F, Ca, P and insoluble extracellular polysaccharide (EPS) concentrations. Data were submitted to one-way ANOVA (repeated measures), followed by Student-Newman-Keuls post-hoc test (p<0.05).
Results: The 250 TMPnano toothpaste promoted the lowest ΔKHN among all groups (p<0.001), and a similar percentage of SH loss when compared with 1100F. Groups treated with 1100F and 250 TMPnano toothpastes presented similar enamel F, Ca, P concentrations. Regarding biofilm data, the highest F concentration was observed for 1100F; Ca content was similar between 1100F and 250 TMPnano, and P content was similar among all groups. Moreover, similar EPS values (p<0.001), ionic activities of CaHPO₄⁰, CaF⁺ and HF⁰ (p<0.05) and degree of saturation of HA and CaF₂ (p<0.05) were observed in biofilm treated with 250 TMPnano and 1100F.
Conclusions: The addition of nano-sized TMP to 250F toothpaste enhanced its anticaries effects, reaching levels similar to those observed for 1100F for most of the variables studied, while the effects of the TMP-containing formulation on the subsurface lesion were significantly higher among all groups.