Protective effect of phosphates and fluoride on the dissolution of hydroxyapatite and their interactions with saliva

MM Manarelli, JP Pessan, ACB Delbem, JG Amaral, Paiva MF, Michele Barbour

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)
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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. 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 (500F); 1100 ppm F (1100F); 1100F/1% TMP; 1100F/8% TMP; 1100/1% TRI; 1100F/8% TRI. In the second phase, HA discs were immersed in pooled human saliva (37º C/ 2h) and treated with PLA; 1100F/1% TMP; 1100F/8% TMP; 1100F/1% TRI; and 1100F/8% TRI. After treatments, final dissolution rate were measured from three consecutive 30-min assays. Statistical analysis were performed using 2-way ANOVA followed by Fisher’s 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 (1100F) significantly reduced HA
dissolution by 20.7%. When fluoride and phosphates were associated, 1100F/1%TMP, 1100F/8%TMP and 1100F/8% TRI showed the highest percentage reductions of dissolution (40.3 to 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.
Original languageEnglish
Pages (from-to)96-101
Number of pages6
JournalCaries Research
Issue number2
Early online date26 Jan 2017
Publication statusPublished - Mar 2017


  • Fluoride
  • Polyphosphates
  • Saliva
  • Pellicle
  • Hydroxyapatite


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