Role of methylmercury exposure (from fish consumption) on growth and neurodevelopment of children under 5 years of age living in a transitioning (tin-mining) area of the western Amazon, Brazil.

Human occupation of the Amazon region has recently increased, bringing deforestation for agriculture and open-cast mining, activities that cause environmental degradation and pollution. Families of new settlers in mining areas might have a diet less dependent on abundant fish and their children might also be impacted by exposures to mining environments. Therefore, there is compounded interest in assessing young children's nutritional status and neurobehavioral development with regard to family fish consumption. Anthropometric (z-scores, WHO standards) and neurologic [Gesell developmental scores (GDS)] development in 688 preschool children (1-59 months of age) was studied. Overall, the prevalence of malnutrition [i.e., moderate stunting (≤2 H/A-Z), underweight (≤2 W/A-Z), and wasting (≤2 W/H-Z) were respectively 0.3% (n = 2), 1.6% (n = 11), and 2.5% (n = 17). Children's mean hair Hg (HHg) concentration was 2.56 µg/g (SD = 1.67); only 14% of children had HHg concentrations lower than 1 µg/g and 1.7% had ≥5 µg/g. The biomarker of fish consumption was weakly but positively correlated with GDS (Spearman r = 0.080; p = 0.035). In the bivariate model, attained W/H-Z scores were not significantly correlated with GDS. A moderate level of GDS deficits (70-84%) was seen in 20% of children. There was significant correlation between family fish consumption and children's hair Hg (HHg) (Spearman r = 0.1756; p < 0.0001) but no significant correlation between children's HHg and W/H-Z scores. However, the multivariate model showed that breastfeeding, a fish consumption biomarker (HHg), maternal education, and child's age were statistically significant associated with specific domains (language and personal-social) of the Gesell scale. In this mining environment, family fish-eating did not affect children's linear growth, but it showed a positive influence (along with maternal variables) on neurodevelopment. Health hazards attendant on a high prevalence of moderate neurodevelopment delays coexisting with exposure to multiple neurotoxic substances merits further investigation in poor environmental settings of tin-mining areas.

Titanium alloy mini-implants for orthodontic anchorage: immediate loading and metal ion release.

Removable osseointegrated titanium mini-implants were successfully used as anchorage devices in orthodontics. The early load is necessary to simplify the mini-implant methodology, but can lead to failure during osseointegration. The Ti-6Al-4V alloy was used instead of commercially pure Ti due to its superior strength. However, the corrosion resistance is low, allowing for metal ion release. The purpose of this work was to analyze the immediately loaded mini-implant fixation and to gauge the vanadium ion release during the healing process. Titanium alloy mini-implants were inserted in the tibiae of rabbits. After 1, 4 and 12 weeks, they were submitted to removal torque testing. There was no increase in the removal torque value between 1 and 4 weeks of healing, regardless of the load. Nevertheless, after 12 weeks, a significant improvement was observed in both groups, with the highest removal torque value for the unloaded group. The kidney, liver and lung were also extracted and analyzed by atomic absorption spectrometry. In comparison with the control values, the content of vanadium increased slightly after 1week, significantly increased after 4 weeks and decreased slightly after 12 weeks, without reaching the 1 week values. A stress analysis was carried out which enables both the prediction of the torque at which commercially pure (CP) Ti and Ti-6Al-4V deform plastically and the shear strength of the interface. This analysis reveals that the removal torques for CP Ti dangerously approach the yield stress. The results of this rabbit model study indicate that titanium alloy mini-implants can be loaded immediately with no compromise in their stability. The detected concentration of vanadium did not reach toxic levels in the animal model.