Abstract / Summary
Objectives: To evaluate the remineralization efficacy and surface effects of 1450 ppm fluoride toothpaste fortified with synthetic hydroxyapatite (Syn-HAP) of varying particle sizes and concentrations on synthetic enamel.
Material and methods: Nano-sized Syn-HAP (nanoSyn-HAP) was synthesized via a mechanochemical process and characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Sixty disc-shaped synthetic pellets underwent artificial caries induction and were randomly divided into five groups: Untreated (negative control), commercial 1450 ppm fluoride toothpaste (FT), FT plus 5% micrometer-sized Syn-HAP (FT+5mHAP), FT plus 5% nanoSyn-HAP (FT+5nHAP), and FT plus 10% nanoSyn-HAP (FT+10nHAP). Specimens then underwent a 15-day pH cycling regimen with twice-daily treatments. Knoop microhardness was evaluated at baseline, post-caries induction, and post-treatment; surface roughness and scanning electron microscopy (SEM) were assessed at baseline and post-treatment. Data were analyzed using ANOVA and Bonferroni post-hoc tests (p < 0.05).
Results: XRD confirmed a pure hydroxyapatite phase, and TEM indicated that 93% of particles were smaller than 50 nm. All toothpaste-treated groups exhibited significant microhardness recovery versus the untreated group (p < 0.05), with no significant differences among them. The untreated and FT groups showed significantly increased roughness after 15 days (p < 0.01), whereas all Syn-HAP groups maintained smoothness comparable to baseline, with significantly lower roughness than FT (p < 0.01). SEM corroborated these findings, revealing smoother surfaces with particle integration in the Syn-HAP groups.
Conclusions: Under the conditions of this in vitro study, supplementing 1450 ppm fluoride toothpaste with Syn-HAP produced surface microhardness recovery that did not differ significantly from that of standard fluoride toothpaste, while significantly improving the preservation of surface smoothness. Syn-HAP-fortified formulations therefore offer a promising approach for caries management, combining effective surface hardening with superior surface integrity, although confirmation in in situ and in vivo settings is required.