Soluble Fluoride in Na2FPO3/CaCO3-Based Toothpaste as an Indicator of Systemically Bioavailable Fluoride

Abstract

Fluoride chemically soluble in toothpaste is an indicator of fluoride bioavailability when the teeth are brushed and the same should be expected systemically when toothpaste is ingested. A four-phases study was conducted, in which eight participants were subjected in each phase to one of the assigned treatment groups: Group I: fresh sample of a Na2FPO3/CaCO3 toothpaste with 1,334 μg F/g of total soluble fluoride (TSF); groups II–IV: aged samples of toothpaste presenting TSF concentrations of 1,128, 808, and 687 μg F/g, respectively. In all phases, the participants ingested an amount of toothpaste equivalent to 70.0 µg F/kg body weight, as total fluoride (TF). Blood was collected before (baseline) and up to 180 min after toothpaste ingestion as indicator of fluoride bioavailability. Total urine (24 h before and 24 h after ingestion) was collected as indicator of absorbed fluoride that was excreted. F concentration in blood plasma and urine was determined with a fluoride ion-specific electrode. The areas under the curve of F concentration vs. time (AUC=ng F/ml x min) and the peaks of fluoride concentration in blood plasma (Cmax) were calculated. The net amount of fluoride excreted (mg/day) was calculated by subtraction. A significant correlation of the amount (mg) of TSF ingested was found between the AUC (r= 0.76; p<0.01) and Cmax (r= 0.86; p<0.01) in plasma, and the fluoride excreted (r= 0.65; p<0.01). For TF no statistical correlations were found (p>0.05). Data suggest that the concentration of TSF found in Na2FPO3/CaCO3-based toothpastes is a useful predictor of how much fluoride will be systemically bioavailable when this type of formulation is ingested.

Remineralizing Potential of Bioactive Glass–Ceramic over White Spot Lesions

“…Additionally, despite dilution in water to create the slurry, sodium fluoride is poorly soluble in water. 27 The ET with Bio showed intermediate surface roughness results, attributed to the presence of Bio particles with an average size of 4 µm. Bio particles are highly bioactive and undergo a rapid multistage surface reaction when in contact with an aqueous media, ultimately resulting in the formation of hydroxycarbonate apatite.…”

“…Additionally, despite dilution in water to create the slurry, sodium fluoride is poorly soluble in water. 27…”

Optimization of a Validated Protocol That Determines Bioavailable Fluoride in Toothpastes

“…Cury et al [1981] have used fluoride ion-specific electrode (F-ISE) by the direct technique to determine total fluoride (TF) and total soluble fluoride (TSF) in toothpastes. The protocol [Cury et al, 2010] is considered feasible, reliable, and inexpensive and was recently validated either to estimate the local bioavailability of fluoride in saliva when the teeth are brushed [Coelho et al, 2020] or the systemic effect when the toothpaste is ingested [Caldas da Rocha et al, 2022]. Other protocols of analysis have been developed [Bijle et al, 2020], but not properly validated in terms of fluoride bioavailability.…”

Dose-response relationship between toothpaste soluble fluoride absorbed in the gastrointestinal tract and saliva fluoride secretion

“…Fluoride toothpaste is a risk factor for dental fluorosis 1 when it is ingested during brushing, but the dose (mg F/day/kg body weight) that children are exposed has been overestimated 2 because it is based on the total fluoride (TF) concentration (soluble + insoluble) present in the toothpaste formulation, but not on the chemically soluble fluoride (TSF = F ion + FPO 3 2− ion) fraction 3 . Dental fluorosis is a hypomineralization of enamel 4 provoked by body circulating fluoride due to fluoride ingestion during enamel formation 5 .…”

“…To discard possible confounding factors, in the present study we used the same Na 2 FPO 3 /CaCO 3 -based toothpaste formulation with 1,450 ppm F of total fluoride, but different concentrations of soluble fluoride. If whole saliva is able to differentiate how much of the total fluoride of a toothpaste formulation is bioavailable to be absorbed in gastrointestinal tract, as shown for blood 3 , a dose-response effect might also be found for saliva. If this dose-response effect is proven, saliva will indeed be able to replace blood to estimate the fluoride bioavailability of toothpastes.…”