Evaluation of novel nanoscaled metal fluorides on their ability to remineralize enamel caries lesions

Matthias Zirk,Julian Lausch,Richard J Wierichs,Sandra Schievelkamp,Marcella Esteves-Oliveira,Hendrik Meyer-Lueckel,Erhard Kemnitz

doi:10.1038/s41598-018-38225-8

Abstract

The aim of this in vitro study was to evaluate the ability of two nanoscaled metal fluorides (NMF) to remineralize shallow (SL) and deep (DL) artificial enamel caries lesions. NMF are synthesized via a non-aqueous fluorolytic sol-gel-synthesis and dissolve low fluoride concentration in aqueous solutions (n-CaF2: 7 ppm, n-MgF2: 70 ppm), whilst containing a nominal fluoride concentration of 3,400 ppm. For comparison, an aqueous sodium fluoride solution (NaF: 3,400 ppm), a sodium fluoride containing varnish (Duraphat: 22,600 ppm) and a fluoride-free negative control were investigated. Bovine enamel specimens with SL (n = 86, 4649–4795 vol%xμm) or DL (n = 145, 9091–9304 vol%xμm) were prepared and allocated to five groups each. In each group the respective agent was applied and pH-cycling was performed for 14 days (SL) and 90 days (DL), respectively. Mineral loss and lesion depth were assessed by transversal microradiography. For SL, all fluoride agents significantly remineralized the specimens compared to baseline (p > 0.05; Mann-Whitney test) to a similar extent. For DL, both NMF showed significantly higher mineral gain compared to the other fluoride agents (p < 0.05). In conclusion, the novel NMF- showing relatively low free fluoride concentrations- bear at least the similar potential for remineralization of early caries lesions as highly fluoridated agents being commonly used.

Highlights

Topical fluorides are commonly applied to prevent caries formation[1,2]
SL specimens treated with NMF and the sodium fluoride applications (NaF), n-CaF2, n-MgF2 and Duraphat showed a significant remineralization (ΔZEffect) compared to ΔZBaseline (p < 0.05; Wilcoxon test + Bonferroni adjustment; Table 1), which was not the case for the negative control (p > 0.05, Table 1)
The results of the present study indicate that nanoscaled metal fluorides, which dissolve low fluoride concentrations in aqueous solutions, promote remineralization of enamel caries lesions to a similar extent compared with a 3,400 ppm F− sodium fluoride solution or Duraphat after a short-term period of 14 days and present a significant greater ability to remineralize enamel caries lesions after an extended period of 90 days

Summary

Introduction

Topical fluorides are commonly applied to prevent caries formation[1,2]. Sodium fluoride (NaF) is the most frequently used fluoride compound[1]. Frequent applications of rather low concentrations of fluorides are recommended to inhibit demineralization and enhance remineralization[5]. Fluoride-containing varnishes (e.g. Duraphat) are applied to promote long-term remineralization by creating loosely bounded calcium-fluoride reservoirs[9]. These slow fluorides releasing CaF2-like reservoirs are not considered to be effective under higher cariogenic conditions[10]. Their influence on remineralization is somehow limited to directly accessible dental surfaces[10]. No significant differences were found for baseline values between groups (Kruskal-Wallis-test, Bonferroni adjusted); n = number sample size per group. Some engineered nanomaterials were developed in order to penetrate into the mineral structure, but their capability of remineralizing the dental enamel structure has not been fully elucidated, yet[4]

Methods

Results

Conclusion