Caries-preventive effect of anti-erosive and nano-hydroxyapatite-containing toothpastes in vitro

OBJECTIVES The aim of the study was to investigate the caries-preventive effect of newly developed fluoride and fluoride-free toothpastes specially designed for erosion prevention. The hypothesis was that these products might also show superior caries-inhibiting effect than regular fluoride toothpastes, since they were designed for stronger erosive acid challenges. MATERIALS AND METHODS Enamel specimens were obtained from bovine teeth and pre-demineralized (pH = 4.95/21 days) to create artificial caries lesions. Baseline mineral loss (ΔZB) and lesion depth (LDB) were determined using transversal microradiography (TMR). Ninety specimens with a median ΔZB (SD) of 6027 ± 1546 vol% × μm were selected and randomly allocated to five groups (n = 18). Treatments during pH-cycling (14 days, 4 × 60 min demineralization/day) were brushing 2×/day with AmF (1400 ppm F-, anti-caries [AC]); AmF/NaF/SnCl2/Chitosan (700 ppm F-/700 ppm F-/3500 ppm Sn2+, anti-erosion [AE1]); NaF/KNO3 (1400 ppm F-, anti-erosion [AE2]); nano-hydroxyapatite-containing (0 ppm F-, [nHA]); and fluoride-free toothpastes (0 ppm F-, negative control [NC]). Toothpaste slurries were prepared with mineral salt solution (1:3 wt/wt). After pH-cycling specimens presenting lesion, surface loss (mainly by NC and nHA) were discarded. For the remaining 77 specimens, new TMR analyses (ΔZE/LDE) were performed. Changes in mineral loss (ΔΔZ = ΔZB - ΔZE) and lesion depth (ΔLD = LDB - LDE) were calculated. RESULTS All toothpastes caused significantly less demineralization (lower ΔΔZ) than NC (p 0.05, ANOVA). CONCLUSION/CLINICAL RELEVANCE While both anti-erosive and anti-caries toothpastes reduced mineral loss to a similar extent, the fluoride-free nano-hydroxyapatite-containing toothpaste seemed not to be suitable for inhibition of caries demineralization in vitro.