Protective Effect of Phosphates and Fluoride on the Dissolution of Hydroxyapatite and Their Interactions with Saliva

Abstract

This study aimed to investigate the effect of phosphates and fluoride, alone or in combination, and the influence of salivary pellicle on hydroxyapatite (HA) dissolution. The baseline dissolution rate of HA discs was measured using a pH-stat system (0.3% citric acid, pH 3.2). In the first series of experiments, HA discs (n = 8/group) were treated with: a placebo solution (PLA, deionised water); sodium trimetaphosphate (TMP), sodium tripolyphosphate (TRI) and sodium pyrophosphate (PYRO) at 1 or 8%; 500 ppm F; 1,100 ppm F; 1,100 ppm F/1% TMP; 1,100 ppm F/8% TMP; 1,100 ppm F/1% TRI; 1,100 ppm F/8% TRI. In the second phase, HA discs were immersed in pooled human saliva (37°C/2 h) and treated with PLA, 1,100 ppm F/1% TMP, 1,100 ppm F/8% TMP, 1,100 ppm F/1% TRI, and 1,100 ppm F/8% TRI. After treatments, final dissolution rates were measured from 3 consecutive 30-min assays. Statistical analyses were performed using 2-way ANOVA followed by the Fisher test (α = 0.05). The type and concentration of phosphate tested significantly influenced HA dissolution; 8% TRI showed the highest reduction (36.9%) among all treatment solutions. Fluoride alone (1,100 ppm F) significantly reduced HA dissolution by 20.7%. When fluoride and phosphates were associated, 1,100 ppm F/1% TMP, 1,100 ppm F/8% TMP, and 1,100 ppm F/8% TRI showed the highest percentage reductions of dissolution (40.3-46.1%). Salivary pellicle led to a greater and more sustained protective effect of the treatment solutions compared to their counterparts without salivary coating. It was concluded that the association of phosphate and fluoride enhanced their protective effect against HA dissolution when compared with these compounds alone, especially in the presence of salivary pellicle.

Film-Forming Polymers for Inhibition of Hydroxyapatite Dissolution: A Screening Study

“…When LPP was associated with fluoride, the same situation was not observed. Although it has been suggested that each polyphosphate has an ideal molar ratio with fluoride [Manarelli et al, 2017], in our study, the combination of LPP in all concentrations with NaF (225 ppm F − ) resulted in similar levels of inhibition of HA dissolution. These results supported the findings that phosphate polymers have a synergetic effect with fluoride against HA dissolution [Scaramucci et al, 2015;Manarelli et al, 2017].…”

“…Although it has been suggested that each polyphosphate has an ideal molar ratio with fluoride [Manarelli et al, 2017], in our study, the combination of LPP in all concentrations with NaF (225 ppm F − ) resulted in similar levels of inhibition of HA dissolution. These results supported the findings that phosphate polymers have a synergetic effect with fluoride against HA dissolution [Scaramucci et al, 2015;Manarelli et al, 2017]. In addition to the ability of adsorbing to HA, it was hypothesized that sodium polyphosphates could retain Ca 2+ and CaF + in their molecule, when fluoride was present, by replacing Na + .…”

“…In terms of limitations of the study, although the pHstat method does not fully reproduce the events that occur in the oral environment, it is suitable for chemical analysis of erosion, as a preliminary assessment of different variables [Barbour et al, 2005[Barbour et al, , 2011Scaramucci et al, 2015;Manarelli et al, 2017], when the experiment involves many groups, as was the case of the present study. Although the dissolution of HA differs quantitatively from the enamel and dentin, which contains other components, a previous study observed that HA had a qualitatively erosion behavior similar to that of enamel and dentin.…”

Fluoride release from two types of fluoride-containing orthodontic adhesives: Conventional versus resin-modified glass ionomer cements—An in vitro study

“…A lot of studies concerning the fluoride release of fluoride varnishes used hydroxyapatite discs as carrying objects [30][31][32]. Fluoride release is a three-dimensional process in which every surface area will release ions, as long as there is contact with the surrounding solution.…”

Self‐perceived oral symptoms and periodontal status among young intravenous heroin addicts: A cross‐sectional case‐control study

“…One explanation for this is a reduction in the salivary flow rate among individuals in the test group. Saliva is a complex oral fluid that besides helping in speech, mastication, and deglutition, protects the teeth and oral mucosal surfaces from pathogenic microbes . In the study by http://Protrka et al., salivary flow was assessed among heroin addicts and nonaddicted controls.…”