Synergistic effect of fluoride and nano-sized TMP in toothpastes against enamel erosion in vitro

Objectives: To assess the effects of a fluoride (F) toothpaste containing nano-sized sodium trimetaphosphate (TMP) on enamel erosion in vitro, as well as the influence of enamel acquired pellicle.
Methods: Bovine enamel blocks (4 mm x 4 mm, n = 120) were selected by surface hardness (SH) and randomly assigned into five experimental groups, according to the toothpastes tested: Placebo (no F or TMP); 1100 ppm F (1100F); 1100F containing 3% micrometric TMP (1100F-TMP); 1100F containing 3% nano-sized TMP (1100F-TMPnano) and 5000 ppm F (5000F). Specimens were also divided into two experimental conditions: erosion in the presence of human saliva (ERO-HS, n = 60) or artificial saliva (ERO-AS, n = 60). The erosive challenge was produced by immersion in citric acid 4x/day (5 minutes each time), followed by a remineralizing period (ERO-HS or ERO-AS) among the erosive challenges. After each erosive challenge, blocks were exposed to slurries of the toothpastes (1 minute). Specimens were analyzed by profilometry (to determine enamel wear), as well as by final SH (SHf) and cross-sectional hardness (∆KHN). Data were submitted to two-way ANOVA followed by the Student-Newman-Keuls test (p < 0.001).
Results: SHf and ΔKHN values were significantly higher in groups treated with 1100F-TMP, 1100F-TMPnano and 5000F toothpastes when compared to Placebo and 1100F (p<0.001); 1100F-TMPnano and 5000F toothpastes had a greater protective effect against enamel wear when compared with the positive control (1100F), regardless the presence of the acquired pellicle (p<0.001).
Conclusions: The addition of TMPnano to 1100F toothpaste significantly increased the protective effect of the product against enamel erosion, reaching levels similar to those obtained after the use of 5000F. The presence of enamel acquired pellicle did not influence the effects of the products tested.