Plasma as an indicator of bone fluoride levels in rats chronically exposed to fluoride.

OBJECTIVE: This study evaluated the use of plasma, bone surface (periosteal) and whole bone as biomarkers of chronic fluoride (F) exposure. METHODS: Forty male Wistar rats were assigned to 4 groups (n=10/gr) that differed according to the F concentration they received in the drinking water. Groups 1, 2, 3 and 4 received water containing 0 (control), 5, 15, and 50 mg F/L, respectively. The rats were killed at 120 days of age. Plasma and femur were collected and analyzed for fluoride with the ion specific electrode by the direct method or after hexamethyldisiloxane-facilitated diffusion. Data were tested for statistically significant differences by ANOVA and linear regression (p<0.05). RESULTS: Mean (+/- SE) plasma F concentrations ranged from 0.030 +/- 0.002 to 0.187 +/- 0.013 (mg/mL). The concentrations in surface and whole bone ranged from 610 +/- 32 to 4,693 222; and 647 +/- 22 to 3,439 +/- 134 microg/g, respectively. The surface/whole F concentration ratios were 0.941, 1.414, 1.173 and 1.377, for groups 1, 2, 3 and 4 respectively. For plasma and whole bone, the difference among all groups was statistically significant, except for group 2 compared to group 1. For bone surface, all groups differed from each other except for group 2 compared to group 3. A significant positive correlation was found between bone surface and whole bone F (r(2)=0.94), as well as between plasma and bone surface (r(2)=0.71) and plasma and whole bone (r(2)=0.74). CONCLUSIONS: Data suggest that both bone surface and whole bone are suitable biomarkers of chronic F exposure in rats and plasma may be used as indicator of bone fluoride levels.

Bone surface and whole bone as biomarkers for acute fluoride exposure.

This study compares fluoride concentrations ([F]) in surface and whole bone for up to 27 days following an acute oral dose of F. Four groups of rats received single oral F dose (50 mg/kg body weight), and the control group received deionized water (n = 10/group). Groups were euthanized at 1, 3, 9, or 27 days after F administration. Plasma and femurs were collected. F on the femur surface was removed from a circular area (4.52 mm(2)) by immersion in 0.5M HCl for 15 s. The solution was buffered with total ionic strength adjustment buffer and analyzed with an electrode. The subjacent bone was sectioned and ashed at 600 degrees C. Ash and plasma were analyzed for F with the electrode following hexamethyldisiloxane-facilitated diffusion. Data were analyzed by Kruskall-Wallis and Dunn's test and by linear regression (p < 0.05). Peak plasma and bone surface [F] occurred on day 1 (0.26 +/- 0.14 microg/mL and 1801 +/- 888 microg/g, respectively). Bone surface [F] at 3, 9, and 27 were not statistically different from control. A significant increase in whole bone [F] was observed 3 days after F administration and the [F] remained relatively constant thereafter. The mean (+/- SD) surface/whole bone [F] ratios for the control and F groups were 2.45 +/- 0.98, 3.92 +/- 1.32, 1.61 +/- 0.82, 1.73 +/- 0.39, and 1.09 +/- 0.28, respectively. Plasma and bone surface [F]s were positively correlated (r = 0.74). Thus, bone surface was found to be a suitable biomarker for acute, sublethal F exposure 1 day after F administration. Whole bone [F] were significantly increased at 3, 9, and 27 days after F administration.

[Comparison of 2 techniques for enamel remineralization]. / Comparação de duas técnicas para remineralização do esmalte.

Six patients enrolled at the Hospital of Rehabilitation of Craniofacial Anomalies, University of São Paulo, aging 16 to 20 years, were selected. All patients presented with white spots in both sides of the superior arch, which totalized 41 spots. The left side of the arch was submitted to remineralization by means of the conventional technique with Reminer, a commercially available product. In the right side, a modified technique was employed, with the utilization of fluoridated dentifrices every night, during 8 weeks. It was observed that successful remineralization occurred in 62% of the spots when the conventional technique was employed, whereas, when fluoridated dentifrices were utilized, there was partial remineralization in 10% of the spots. The utilization of Reminer was more effective than the utilization of fluoridated dentifrices.