Effect of iron II on hydroxyapatite dissolution and precipitation in vitro.

The aim of this study was to evaluate the effect of iron II on the dissolution and precipitation of synthetic hydroxyapatite (HA). HA powder was suspended in solutions of iron (0.84 µg/ml, Fe0.84; 18.0 µg/ml, Fe18; 70.0 µg/ml, Fe70), fluoride (1,100 µg/ml, F1,100), and deionized water and submitted to pH cycling. After pH cycling, the samples were analyzed by infrared spectroscopy and X-ray diffraction. The concentrations of fluoride, calcium, phosphorus, and iron were also analyzed. The data were submitted to ANOVA, and analyzed by Tukey's test (p < 0.05). The infrared spectrum showed a reduction in all bands corresponding to phosphates and hydroxyls and an increase in the carbonate band in the groups with iron. The intensity of the phosphate bands increased and that of the hydroxyl bands decreased in the group F1,100. It was observed that there was a higher concentration of Ca in the group F1,100, with no significant difference between the groups Fe18 and Fe70 (p > 0.05). There was an increase in Fe concentration in the HA directly related to the Fe concentration of the treatment solutions. Results show that the presence of Fe causes the precipitation of apatite with high solubility.

Effect of mouth rinses with fluoride and trimetaphosphate on enamel erosion: an in vitro study.

The effect of mouth rinses containing fluoride (100 µg/ml) and sodium trimetaphosphate (TMP) on enamel erosion was evaluated in vitro. Bovine enamel blocks were subjected to erosive challenges 4 times per day for 5 min, followed by treatment with placebo, 225 µg F/ml, 100 µg F/ml, 100 µg F/ml and TMP (0.2, 0.4 and 0.6%) solutions (30 s) and storage in artificial saliva, over a duration of 5 days. TMP groups showed lower enamel wear than fluoride-only and placebo groups (p < 0.05). Addition of TMP at a TMP:NaF molar proportion between 1.24:1 and 3.72:1 to a solution containing 100 µg F/ml presented a greater protective effect under erosive conditions than a solution containing 225 µg F/ml, in the absence of TMP.

Effect of different fluoride concentrations of experimental dentifrices on enamel erosion and abrasion.

It has been suggested that fluoride products are able to reduce erosive tooth wear. Thus, the purpose of this in vitro study was to evaluate the effect of dentifrices with different fluoride concentrations as well as of a low-fluoridated dentifrice supplemented with trimetaphosphate (TMP) on enamel erosion and abrasion. One hundred twenty bovine enamel blocks were assigned to the following experimental dentifrices: placebo, 1,100 microg F/g, 500 microg F/g plus 3% TMP and 5,000 microg F/g. The groups of enamel blocks were additionally subdivided into conditions of erosion (ERO) and of erosion plus abrasion (ERO + ABR). For 7 days, the blocks were subjected to erosive challenges (immersion in Sprite 4 times a day for 5 min each time) followed by a remineralizing period (immersion in artificial saliva between erosive challenges for 2 h). After each erosive challenge, the blocks were exposed to slurries of the dentifrices (10 ml/sample for 15 s). Sixty of the blocks were additionally abraded by brushing using an electric toothbrush (15 s). The alterations of the enamel were quantified using the Knoop hardness test and profilometry (measurements in micrometers). The data were analyzed using a 2-way ANOVA test followed by a Bonferroni correction (p < 0.05). In in vitro conditions, the 5,000 microg F/g and 500 microg F/g plus 3% TMP dentifrices had a greater protective effect when compared with the 1,100 microg F/g dentifrice, under both ERO and ERO + ABR conditions. The results suggest that dentifrices alone are not capable of completely inhibiting tooth wear.

In vitro evaluation of dentifrice with low fluoride content supplemented with trimetaphosphate.

One way to reduce dental fluorosis is by reducing the fluoride (F) concentration in dentifrice, but low-F dentifrice should be as effective as a standard dentifrice. This study evaluated in vitro whether the supplementation with sodium trimetaphosphate (TMP) of a dentifrice with low F content (500 microg/g) would provide a similar effect to that of a standard dentifrice. Bovine enamel blocks were submitted to a pH cycling regime incorporating daily exposures to a slurry of dentifrice: a low-F dentifrice with or without 0.1-3.0% TMP; an F-free, phosphate-free dentifrice (negative control), or a dentifrice with 1,100 microg/g F (positive control). The addition of TMP to dentifrice with or without F was associated with higher surface hardness and decreased loss of integrated subsurface hardness after pH cycling. The combination of 1% TMP and 500 microg F/g had a greater effect than the positive control dentifrice. It is concluded that the addition of TMP to the 500-microg F/g dentifrice allowed a similar or larger effect as compared with a standard dentifrice in this in vitro model.

Comparison of methods for evaluating mineral loss: hardness versus synchrotron microcomputed tomography.

This study analyzed degrees of demineralization in bovine enamel using synchrotron microcomputed tomography (SMCT) and hardness measurements (Knoop hardness number, KHN). For 5 days, 40 bovine enamel blocks were individually subjected to a pH cycling model and treatment with fluoride dentifrices (placebo, 275, 550 and 1,100 microg F/g) diluted in deionized water twice a day. Surface hardness number and cross-sectional profiles of hardness and mineral concentration (by SMCT) were determined. Integrated hardness (KHN x microm) for sound and demineralized specimens was calculated and subtracted to give the integrated loss of hardness (DeltaKHN) for the lesions. Increasing fluoride concentration in the dentifrices led to higher values for surface hardness after pH cycling and mineral concentration (g(HAp) cm(-3)), and lower values for DeltaKHN (p < 0.05). From the present results, it may be concluded that hardness measurements revealed demineralization in all groups, which was lower in groups treated with dentifrice with a higher F concentration. SMCT and hardness measurements gave similar results in areas with higher demineralization, but diverged in areas with lower demineralization.

In vitro evaluation of the effectiveness of acidic fluoride dentifrices.

This study evaluated the effectiveness of acidic low-fluoride dentifrices compared to conventional neutral dentifrices. Enamel blocks were submitted to pH cycling and treatment with slurries of dentifrices containing 0, 275, 412, 550 and 1,100 microg F/g (pH 4.5 or 7.0), and also a commercial dentifrice (1,100 microg F/g) and a commercial children's dentifrice (500 mug F/g). Variations in surface microhardness and in the mineral content in enamel after pH cycling were calculated. Enamel blocks treated with acidic dentifrices exhibited less mineral loss compared to neutral dentifrices (ANOVA; p < 0.05). The acidic dentifrices with 412 and 550 microg F/g had the same effectiveness as the neutral 1,100-microg F/g dentifrice and commercial 1,100-microg F/g dentifrice.

Glucose metabolism in the erythrocytes of the buffalo (Bubalus bubalis).

14CO2 production from [1-14C] glucose, the rate of glycolysis measured by the value of lactate production and the activities of various enzymes were determined in buffalo erythrocytes. Buffalo red cell glycolytic metabolites were estimated and used for the calculation of the mass action ratios of reactions catalyzed by the glycolytic enzymes of Bubalus bubalis. A comparison of the values of the mass action ratios with the equilibrium constants of the various glycolytic reactions indicate that hexokinase, phosphofructokinase, phosphoglycerate kinase and pyruvate kinase reactions are displaced from equilibrium, suggesting a regulatory role for each of these enzymes in buffalo erythrocyte glycolysis.

In situ evaluation of low-fluoride toothpastes associated to calcium glycerophosphate on enamel remineralization.

OBJECTIVES: This study aimed to evaluate the effect of low-fluoride toothpastes with calcium glycerophosphate (CaGP) on enamel remineralization in situ. METHODS: Volunteers (n=10) wore palatal devices holding four bovine enamel blocks. The treatments involved 5 experimental phases of 3 days each according to the following toothpastes: placebo, 500 ppm F (500 NaF), 500 ppm F with 0.25% CaGP (500 NaF CaGP), 500 ppm F with 0.25% CaGP (500 MFP CaGP) and 1100 ppm F (1100; positive control). After this experimental period, the fluoride, calcium, and phosphorus ion concentrations from enamel were determined. Surface and cross-sectional hardness were also performed. Data were analysed by 1-way ANOVA, Student-Newman-Keuls' test and by Pearson's correlation. RESULTS: The addition of 0.25% CaGP improved the remineralization potential of low-fluoride toothpastes and the NaF as source of fluoride yielded the best results (p<0.001) as evidenced by the hardness analysis. The 1100 ppm F toothpaste provided higher presence of fluoride in the enamel after remineralization (p<0.001). The addition of CaGP to the NaF and MFP toothpastes led to similar calcium concentration in the enamel as the observed with the positive control (p=0.054). CONCLUSIONS: Toothpastes with 500 ppm F (NaF or MFP) and CaGP showed similar remineralization potential than 1100 ppm F toothpaste. CLINICAL SIGNIFICANCE: Toothpastes containing 500 ppm F associated to CaGP, with both fluoride source (NaF or MFP), showed a potential of remineralization similar to commercial toothpaste. Although there is a need for confirmation in the clinical setting, these results point to an alternative for improving the risk-benefit relationship between fluorosis and dental caries in small children.

Effect of rinsing with water immediately after neutral gel and foam fluoride topical application on enamel remineralization: An in situ study.

OBJECTIVE: The aim of this study was to evaluate, in situ, the effect of rinsing with water immediately after neutral fluoride foam application (Foam) or fluoride gel application (Gel). DESIGN: Ten volunteers wore acrylic palatal appliances containing 4 enamel blocks selected by surface hardness with artificial caries. Five experimental regimes of 3 days each were set according to treatment: placebo; Gel and Foam followed by no rinsing or consuming of liquids or solids for the next 30min; Gel and Foam followed by immediately washing with water jet. After each phase, surface hardness was again measured for analysis of mineral gain, evaluated through percentage of surface hardness recovery (%SHR) and integrated loss of subsurface hardness (ΔKHN). The concentration of loosely bound fluoride (CaF2) and firmly bound fluoride (FA-like) formed and retained were also determined. RESULTS: Fluoride treatments produced greater remineralization (%SHR and ΔKHN) compared to placebo group (p<0.05). There was no difference in the ability to promote remineralization and in the concentration of fluoride formed and retained, in each analysis, between Gel and Foam (p>0.05). CONCLUSION: The data suggest that rinsing with water immediately after topical application does not seem to have an influence on the ability of fluoride to promote remineralization.

In vitro evaluation of acidified toothpastes with low fluoride content.

Fluoride toothpastes are a risk factor for the development of dental fluorosis. Products with low fluoride content offer a higher security, but their effectiveness must be proven. The aim of this in vitro study was to compare two acidified toothpastes with low fluoride concentration (412 and 550 microg F/g) with neutral toothpastes. Bovine enamel blocks were selected by surface microhardness (SMH) and randomized to twelve groups of 13, according to the fluoride concentration in toothpaste (placebo, 275, 412, 550 or 1,100 microg F/g) and pH (7.0 or 5.5). Two commercially available toothpastes were also studied: a 1,100-microg F/g, pH 7.0 paste (positive control) and a children's paste (500 microg F/g, pH 7.0). The blocks were subjected to pH cycling for 7 days. The toothpaste treatment was done twice daily. Surface and cross-sectional microhardnesses were assessed to calculate the percentage change of SMH (%SMH) and the mineral loss (DeltaZ). The amount of fluoride, calcium and phosphorus in the solutions after the pH cycling was also analyzed. Compared to neutral toothpastes, the acidified toothpastes reduced the %SMH in all F concentrations. Higher F and lower Ca and P concentrations were found in solutions for the acidified toothpastes. Regarding DeltaZ, only the positive control, 1,100-microg F/g (acidified and neutral) groups were not statistically different. The acidified toothpastes showed a dose-response relationship with all variables. For the low-fluoride toothpastes evaluated, only the 550-microg F/g acidified paste had the same anticariogenic action as the 1,100-microg F/g neutral paste.

Metabolism of carbohydrate in vitro of the submandibular salivary glands (SMG) from mice injected with isoproterenol.

The effect of a single dose of isoproterenol, a beta-adrenergic drug, on the metabolism of carbohydrate in vitro of SMG from mice was studied. At the end of 30 and 60 min of incubation the slices of SMG from the experimental groups, sacrificed from 2 to 18 hr after injection of IPR, presented higher glucose uptake. At the end of 60 min of incubation slices of SMG from mice injected with IPR and sacrificed from 2 to 28 hr after the stimulation, formed quantitatively more lactate. After the incubation periods in the presence of glucose, glycogen content was higher for the SMG from the experimental groups.

Changes in some metabolites contents of the carbohydrate metabolism in mouse submandibular salivary gland after stimulation by isoproterenol.

1. The effect of isoproterenol, a beta adrenergic drug, on the metabolism of carbohydrates in the submandibular salivary glands of mice was studied. 2. Alterations in the concentration of some three carbon metabolites were observed in groups of animals killed at various times after the stimulation. 3. Citrate was also determined showing some variation in its contents.

The effect of isoproterenol on some aspects of the anaerobic metabolism of carbohydrates in mouse submandibular gland.

1. The effect of isoproterenol, a beta-adrenergic drug, on some aspects of the anaerobic metabolism of carbohydrates in the submandibular salivary glands of mice was studied. 2. Alterations in enzymatic activities and in the concentrations of some metabolites were observed in groups of animals killed at various times after the stimulation. 3. The potential capacity of the pentose phosphate cycle was greater than that of glycolysis up to 20 hr after the stimulation.