Are fingernail lead levels a reliable biomarker of lead internal dose?

BACKGROUND: Potentially toxic elements, such as lead, can bioaccumulate and alter human physiology. Human biomonitoring is an essential tool to evaluate chemical exposures in different biological matrices (blood, urine, saliva, nails, and hair). Of these biological matrices, nails are favorable for their ease of sampling, transport and storage. The aim of this study was to investigate possible correlations between blood lead levels (BLL) and washed and non-washed fingernail lead levels (FLL) in 55 adults living in a lead-contaminated area. METHOD: Venous blood and fingernail (thumbs and forefingers) samples were collected. Nails from the left hand were washed with Triton X-100 (0.5 % m/v) and HNO3 solution, while nails from the right hand were not submitted to the pre-analytical procedures. Samples were analyzed by graphite furnace atomic absorption spectrometry, and pairwise correlations were used to correlate lead concentrations between BLL and FLL; nails from fingers of the same hand and between washed and unwashed fingernails. Principal component analysis was performed and scatter diagrams were plotted to investigate correlations. RESULTS: A non-significant positive correlation was found between BLL and washed forefinger nails lead (r = 0.219, p = 0.112) and between BLL and thumbnail lead levels (r = 0.182, p = 0.191). Comparison of fingernails from the same hand (thumb and forefinger), showed that lead concentrations of non-washed nails varied widely, even on analyses of transversal fragments from the same nail. Lead levels in non-washed forefinger nails were not correlated with non-washed thumbnails (r = 0.169, p = 0.219). Conversely, washed thumb and forefinger nails were found to be correlated (r = 0.39, p = 0.003). Washed and non-washed nails were also found to be correlated (p < 0.0001). CONCLUSION: In conclusion, the results showed that non-washed nails are not a reliable biomarker for lead exposure. Although washing nails before analysis may reduce external contamination, the correlation of lead concentrations between fingers is poor for fingernail lead levels to serve as an internal dose biomarker to lead exposure. In addition, levels in washed nails were not significantly correlated with blood lead levels. Fingernail lead levels seem to serve as an indicator of lead exposure sources in contact with the individual, but not as a reliable biomarker of internal dose.

Resin-Based Materials Protect Against Erosion/Abrasion-a Prolonged In Situ Study.

While patient compliance is key to preventive measures related to dental erosion, the application of resin-based materials could serve as an additional treatment to inhibit erosion progression. This in situ study evaluated the effect of applying resin-based materials, including resin infiltrant, on previously eroded enamel subjected to prolonged erosive and abrasive challenges. The factors under study were types of treatment (infiltrant [Icon], sealant [Helioseal Clear], adhesive [Adper Scotchbond Multi-Purpose Plus], and control [no treatment]); wear conditions (erosion [ERO] and erosion + abrasion [ERO + ABR]) and challenge time (5 and 20 days) in a single-phase study. The blocks were prepared from bovine enamel, eroded (0.01 M HCl, pH 2.3 for 30 seconds) and randomized among treatments, wear conditions, and volunteers. The application of resin-based materials followed the manufacturers' recommendations. Twenty-one volunteers wore the palatal intraoral device, in which one row corresponded to ERO and the other to ERO + ABR. In each row, all treatments were represented (2 blocks per treatment). For 20 days, the erosive challenge was performed 4 times/day (immersion in 0.01 M HCl, pH 2.3, for 2 minutes) for the ERO condition. For the ERO + ABR condition, two of the erosive challenges were followed by abrasion for 15 seconds with fluoride dentifrice slurry. Enamel and/or material loss was measured using profilometry (initial, after treatment, and after the end of the fifth and 20th days of in situ erosive challenge) and analyzed by ANOVA models and Tukey's test (α=0.05). The results showed that the application of resin-based materials did not cause superficial enamel loss. The infiltrant group showed a thicker layer of material above the enamel compared with the other materials (p=0.001). After the erosive challenge, there was no difference between the conditions ERO and ERO + ABR (p=0.869). All materials protected the enamel against erosion progression compared with the control group (p=0.001). Based on these results, we conclude that the application of resin-based materials results in protection of previously eroded enamel subjected to in situ erosive and abrasive challenge for 20 days.

Treatment of Dentin Hypersensitivity Using Nano-Hydroxyapatite Pastes: A Randomized Three-Month Clinical Trial.

OBJECTIVES: This randomized clinical trial tested the three-month desensitizing effect of two protocols using nano-hydroxyapatite formulations compared with Pro-Argin and fluoride varnish. METHODS: Twenty-eight subjects with 137 teeth presenting dentin exposure with a minimal hypersensitivity of four on the visual analog scale (VAS) took part of this study. The subjects were randomly assigned to four groups: Desensibilize Nano-P paste (20% hydroxyapatite [HAP], potassium nitrate, and sodium fluoride [NaF]; 9000 ppm fluoride [F]); Desensibilize Nano-P associated with experimental home-care pastes (10% HA, potassium nitrate, and NaF; 900 ppm F); Pro-Relief professional paste (8% arginine with Pro-Argin technology) associated with home-care toothpaste (8% arginine, sodium monofluorophosphate, 1450 ppm F); and Duraphat professional varnish (NaF varnish, 22,600 ppm F). The professional treatments were performed in weekly appointments over three weeks. The home-care products were used continuously for three months. A VAS was used to assess the tooth sensitivity response after standardized evaporative stimulus at baseline and after one month and three months. The baseline score was deducted from the final score, and the means were analyzed using nested analysis of variance, while the comparison between times was performed by a general linear model (p<0.05). RESULTS: At the first month all treatments were effective, but there were no significant differences among them (p=0.94). At the third month, despite the fact that NaF varnish had the lowest effect in reducing hypersensitivity, no significant difference was found among the treatments (p=0.09). Only Pro-Relief increased its effect over time (p=0.049). CONCLUSIONS: Nano-hydroxyapatite formulations (with or without home->care product association) were as effective as the other treatments in reducing dentin hypersensitivity over three months.