Improved Enamel Acid Resistance by Highly Concentrated Acidulated Phosphate Sodium Monofluorophosphate Solution

Abstract

Sodium monofluorophosphate (MFP) is a component of fluoride-containing dentifrices and is more biosafe than the conventional sodium fluoride (NaF). MFP can respond not only on the tooth surface layer but also deep into the enamel. We aim to confirm that high concentrations of acid phosphate MFP (AP-MFP, 9000 ppmF), used in professional care, could lead to a highly biosafe fluoride application method that acts through the deep enamel layers. Sample groups were respectively treated in vitro with NaF, acidulated phosphate fluoride (APF), MFP, and AP-MFP, and the samples were compared against an untreated group. Characterizations after fluoride application confirmed that MFP and AP-MFP treatments improved the acid resistance of enamel compared to that of conventional methods. Furthermore, the acid resistance of highly concentrated MFPs improved by using phosphoric acid. Although the acid resistance from the AP-MFP method is not as good as that using APF, AP-MFP can act both on the surface layer and deep into the enamel. Moreover, AP-MFP retains fluoride ions as much as APF does on the tooth surface. The proposed fluoride application method using AP-MFP introduces a dental treatment for acid resistance that is highly biosafe and penetrates deep layers of the enamel.

Inhibition of Citric Acid-Induced Dentin Erosion by an Acidulated Phosphate Sodium Monofluorophosphate Solution

“…A substantial reduction in dentin loss was observed in the AP-MFP and dual groups, similar to that in the conventional APF group, after citric acid demineralization (Figure 1). These findings align with previous research indicating the capacity of MFP to enhance the acid resistance of hydroxyapatite (HAP) and dentin, as well as with the results of a study that used surface application of AP-MFP to enamel at a concentration of 9000 ppmF [13,22,23]. APF application reduced enamel loss to a more significant extent than AP-MFP application; however, there was no difference in dentin loss between the AP-MFP and APF groups in this study [23].…”

“…These findings align with previous research indicating the capacity of MFP to enhance the acid resistance of hydroxyapatite (HAP) and dentin, as well as with the results of a study that used surface application of AP-MFP to enamel at a concentration of 9000 ppmF [13,22,23]. APF application reduced enamel loss to a more significant extent than AP-MFP application; however, there was no difference in dentin loss between the AP-MFP and APF groups in this study [23]. This suggests that the improvement in acid resistance achieved by AP-MFP may be higher in dentin than in enamel.…”

“…In particular, the formation of many secondary particles larger than the expected size of CaF 2 particles was observed in the AP-MFP group, which may have caused the surface roughness in the AP-MFP group to be higher than in the APF group (Figures 2 and 4). It has been shown that APF is superior to AP-MFP in terms of dentine acid resistance in the surface layer of enamel (at 5-10 µm) [23,28]. The surface roughness results in this study may indicate that APF is superior to AP-MFP in terms of acid resistance in the surface layers of dentin and enamel.…”

“…In acidic environments, NaF forms an intermediate product known as dicalcium phosphate dihydrate (CaHPO 4 •2H 2 O), which effectively facilitates the incorporation of fluoride ions into HAP [35]. It has been reported that AP-MFP, similar to NaF, may have mechanisms that promote fluoride ion uptake into enamel in acidic environments [23]. Two hypotheses have been proposed regarding the mechanism by which MFP enhances acid resistance in the dentin when applied to the dental surface.…”

Eficacia De Los Fluoruros Para La Prevención De Caries Dental: Una Revisión Narrativa

“…En su composición se describe un 1.23 % o 2 % de fluoruro de sodio y 0.34 % de ácido fluorhídrico. El fosfato se presenta en forma de ácido ortofosfórico a una concentración de 0.98 % (Satou et al, 2022).…”