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

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.

Cyclotriphosphate associated to fluoride increases hydroxyapatite resistance to acid attack.

This study evaluated the effect of sodium trimetaphosphate (TMP) associated or not with fluoride (F) on the structure and dissolution of carbonated hydroxyapatite (CHA). Synthetic CHA powder (1.0 g) was suspended in solutions containing TMP at 0-10%, associated with 0, 1100, 4500, or 9000 ppm F, and the precipitates were submitted to a pH cycle (n = 6/group). Samples were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. F, calcium (Ca) and phosphorous (P) concentrations were determined in CHA, while P and F were analyzed in the supernatants. Data were submitted to analysis of variance, Student-Newman-Keuls' test and Pearson's correlation coefficient (α = 0.05). Solutions containing 1100 ppm F with TMP between 2-4% and 4500 and 9000 ppm F with TMP between 4 and 8% led to higher Ca/P ratio (p < 0.05) in CHA. Alkali-soluble F deposition was directly related to TMP concentrations whereas an inverse pattern was observed for acid-soluble F incorporation (p < 0.05). Greater P adsorption in the CHA structure was observed with increasing concentrations of TMP for the 0 and 1100 ppm F solutions (p < 0.05). All diffractograms and FTIR spectra showed a similar pattern to that for pure hydroxyapatite. Thus, when TMP and F are coadministered, TMP interferes with F deposition on CHA, and an ideal TMP:F ratio can enhance the precipitation of CHA with lower solubility. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2553-2564, 2018.

Green synthesis of silver nanoparticles combined to calcium glycerophosphate: antimicrobial and antibiofilm activities.

AIM: To synthesize, characterize and evaluate the antimicrobial and antibiofilm activities of novel nanocomposites containing silver nanoparticles (AgNPs) associated or not to ß-calcium glycerophosphate. MATERIALS & METHODS: These nanocomposites were produced through a 'green' route using extracts of different parts of pomegranate. Antimicrobial and antibiofilm properties against Candida albicans and Streptococcus mutans were determined by the minimum bactericidal/fungicidal concentration and biofilm density after treatments. RESULTS: All extracts used were successful in producing AgNPs. Composites made with peel extracts showed the highest antimicrobial and antibiofilm activity against both microorganisms tested and performed similarly or even better than chlorhexidine. CONCLUSION: AgNPs associated or not to calcium glycerophosphate produced by a 'green' process may be a promising novel antimicrobial agent against oral microorganisms.

Longitudinal evaluation of fluoride levels in nails of 18-30-month-old children that were using toothpastes with 500 and 1100 µg F/g.

OBJECTIVES: This study aimed to evaluate the fluoride concentration in the fingernails and toenails of children aged 18-30 months during use of fluoride-containing toothpastes supplemented with calcium glycerophosphate (CaGP) or sodium trimetaphosphate (TMP). METHODS: According to the toothpaste used, children (n = 56) were randomly assigned into three groups: 500 µg F/g with 1% TMP, 500 µg F/g with 0.25% CaGP, and 1100 µg F/g. Fingernails and toenails were collected monthly over a period of 330 days, from the beginning of toothpaste use. Fluoride concentration in the water consumed by the volunteers and fluoride intake from diet and toothpaste were also determined. Fluoride analyses were performed with the electrode after hexamethyldisiloxane-facilitated diffusion or by the direct method, according to the samples. Data passed normality and homoscedasticity tests and were analyzed by 2-way analysis of variance (anova) and 1-way anova followed by Student-Newman-Keuls test (P < 0.05). RESULTS: Fluoride levels in the fingernails and toenails as well as fluoride intake from toothpaste were similar for the groups treated with 500 µg F/g with 1% TMP and 500 µg F/g with 0.25% CaGP toothpastes, but significantly lower than the 1100 µg F/g group (P < 0.05). No significant differences were noted among the groups regarding fluoride intake from diet and that by water consumed by the volunteers (P > 0.05). CONCLUSION: The results of the longitudinal study suggest that the level of fluoride present in nails was lower with the use of toothpastes with a low fluoride concentration.