Lead associated caries development in children living in a lead contaminated area, Thailand

In an observational cross-sectional design, a sample of 292 children aged 6-11 years from two primary schools around a shipyard area, known to be an area contaminated with lead (from the industry), were examined to verify the cariogenicity of lead. The number of decayed and filled surfaces on deciduous teeth (dfs), and the number of decayed, missing, and filled surfaces on permanent teeth (DMFS), the salivary flow rate, pH, buffer capacity, oral hygiene, Lactobacillus spp. and mutans streptococci counts were recorded. The mean (range) of DMFS and dfs were respectively 1.3 (range 0-17) and 13.2 (range 0-45); and the geometric mean blood lead level (PbB) and SD were 7.2 and 1.5 microg/dl. The level of dfs, but not DMFS correlated with the blood lead level (R(s)=0.25, p=0.00 / R(s)=0.09, p=0.14). The odds ratio for DMFS>or=1 and dfs>5 for a doubling of PbB after adjusting for other factors were 1.28 (95%CI, 0.81-2.04; p value=0.35) and 2.39 (95%CI, 1.36-4.20; p value=0.004), respectively. The cariogenicity of lead is evident in deciduous teeth but not in permanent teeth for this age group.     

Chemical composition of enamel and dentine in primary teeth in children from Thailand exposed to lead

Enamel and dentine in teeth of children with high blood levels of lead were analyzed by means of secondary ion mass spectrometry (SIMS) and X-ray micro-analyses (XRMA) and compare with teeth from children with low blood levels of lead. The SIMS analysis revealed detectable levels of Pb in dentine close to the pulp. The XRMA analyses could not detect any lead. There were no differences found in lead level in enamel of high lead level exposed teeth from low level exposed. The results confirm that children with high blood levels of lead have an uptake of lead in dentine close to the pulp.     

Influence of polyacrylic acid (PAA)/Na2HPO4 mixture on biphasic calcium phosphate cement: Enhancing strength and cell viability

This study has investigated the effect of combination of new liquid phase mixture of disodium hydrogen phosphate (Na₂HPO₄) and polyacrylic acid (PAA) on the compressive strength, setting time, bioactivity, and cytotoxicity of biphasic calcium phosphate cement. The PAA was known as one of water-soluble and biocompatible polymers to improve the mechanical performances of the bone cement, but it usually inhibits the phase conversion to hydroxyapatite after the cement has already set. The aim of this work was to evaluate the incorporation of the mixture of PAA and Na₂HPO₄ into biphasic cement. We have found the crucial concentration for adding PAA/Na₂HPO₄ at 30:70 v/v% to enhance the mechanical strength, cell viability, and maintain bioactivity. The phase composition and crosslinking reaction between PAA and alpha-tricalcium phosphate (α-TCP) powder were detected by XRD and FTIR techniques. The beta-tricalcium phosphate (β-TCP) was added in the formula to achieve the biphasic cement, which composed of β-TCP and apatite/calcium deficient-hydroxyapatite (CD-HA) in the final product. The biphasic granule commercial product was used as comparison in the cell viability test. This work had been confirmed that the cement was a nontoxic material. Therefore, our results suggest that the PAA/Na₂HPO₄ could be beneficial for further clinical applications.     

Morphology of enamel in primary teeth from children in Thailand exposed to environmental lead

Lead is one of the major environmental pollutants and a health risk. Dental hard tissues have a capacity to accumulate lead from the environment. Eighty exfoliated primary teeth were collected from children residing around a shipyard area in southern Thailand, known for its lead contamination. The morphology of the enamel was examined by polarized light microscopy (PLM), microradiography (MRG), and scanning electron microscopy (SEM). The specimens derived from two groups of children, one group with high blood levels of lead (57 teeth) and one group having low blood levels of lead (23 teeth). The enamel irrespective of group appeared normal. However, in a majority of the specimens the enamel surface appeared hypomineralized, which was confirmed in SEM. No morphological changes connected to lead in blood could be found. The hypomineralized surface zone could possibly be attributed to an acid oral environment.     

Structural evaluation of ZnO substitution for CaO in glass ionomer cement synthesized by sol-gel method and their properties

Journal of Materials Science - The substitution of ZnO for CaO site and the limitation of ZnO addition in the sol-gel ionomer glass composition at different calcination temperatures were evaluated...