Helene Meyer Tvinnereim

Heavy metals in human primary teeth: some factors influencing the metal concentrations

Human primary teeth have been used as indicators of heavy metal exposure for several decades, but the knowledge about the influence of factors such as tooth type and the presence of caries and roots on metal concentrations is limited. Samples of tooth powder from more than 1200 Norwegian primary teeth without fillings have been analyzed for lead, zinc and cadmium content, and 554 of them for mercury. The material represents all groups of tooth types (incisors, canines and molars), carious and non-carious teeth, and teeth with and without roots. Here we investigate how tooth group and the presence of caries and roots are related to metal concentrations in the teeth. We find that carious teeth have higher metal concentrations than non-carious teeth; the difference was statistically significant for lead, mercury and zinc. Teeth with roots have higher lead and zinc concentrations than teeth without roots. We find differences in metal concentrations between the tooth groups for lead, mercury and zinc. Significant, positive correlations are found between lead and the three other metals and between mercury and zinc. We conclude that metal concentrations in primary teeth are affected by the presence of caries and roots and by tooth group.

Zinc in primary teeth from children in Norway.

Human primary teeth have been used as indicators of exposure to several heavy metals both in Norway and elsewhere. Local dentists in all 19 counties of Norway collected 2747 primary teeth during 1990-1994. Samples of tooth powder from whole, ground teeth were analyzed for zinc concentration by flame atomic absorption spectrophotometry. The overall geometrical mean was 144.5 micrograms of Zn/g of tooth substance (S.D. = 1.6). The result represents a small increase (5.2%) compared with a similar investigation in the 1970s. However, the mean zinc concentrations in the geographically matching parts of the two materials did not differ significantly. The variation in tooth zinc concentrations between the different counties declined from the 1970s to the 1990s. We found no correlation between the tooth zinc concentration and available environmental data on zinc in drinking-water, discharge of zinc from industrial point sources or population density in the same geographical areas. The zinc concentrations varied significantly with caries status, tooth type and root length. Few samples had a zinc concentration below 90 micrograms/g, indicating that most children consume sufficient zinc. Some very high values could not immediately be explained, but may be caused by contamination from zinc-containing dental restorations.

Lead in primary teeth from Norway: changes in lead levels from the 1970s to the 1990s

Lead is one of the most important and widely distributed pollutants in the environment. In the human population children are particularly at risk. Local dentists in all 19 counties in Norway collected 2746 primary teeth from 1990 to 1994. Tooth substance from whole, ground teeth were analyzed for lead concentration by electrothermal atomic absorption spectrophotometry. The geometrical mean for the entire material was 1.27 micrograms lead/g tooth substance (S.D. 1.87). The mean lead levels in each of the counties were significantly lower than those obtained in a corresponding study in the 1970s. Two counties, Oslo and Vest-Agder, had significantly higher lead levels than the majority of the other counties. Tooth lead concentration and atmospheric deposition of lead in the same areas were significantly and positively correlated, as shown by analysis of naturally growing moss. We conclude that lead concentrations in primary teeth from children in Norway have been reduced by approx. 50% from the 1970s to the 1990s. The reduction probably reflects a decrease in the environmental lead burden in Norway.

Trace elements in primary teeth from six areas in Hungary

One hundred and eighty five primary teeth were in 1989–90 collected by local dentists from six different areas in Hungary. The teeth were analyzed for lead, cadmium, mercury and zinc. Both rural, industrialized and urban areas were represented. It was found that the city of Veszprem had significantly higher tooth lead levels than the other areas investigated, including the capital. Two areas had significantly higher tooth‐mercury levels than the other areas, but were just represented by four and six primary teeth, respectively. No area had significantly different cadmium or zinc levels than the other areas investigated. Further study of lead levels in primary teeth from Hungary is suggested.

Lead in deciduous teeth from larger cities of some countries

Altogether 4805 whole primary teeth from Norway, Portugal, Thailand, Hungary, Poland and Chile have been analyzed for lead. The teeth represented named urban, rural and industrialized areas, including the capitals of those countries. It was found that with the exception of teeth from Bangkok, which had a significantly higher tooth lead level than other Thai and foreign teeth, all capitals were either significantly lower or not significantly different from the level of the respective whole country, including the capital. The material represented times and countries where unleaded gasoline was not yet in common use. It is concluded that leaded gasoline may not be a primary source of lead burden in children in a country as a whole.

Qualitative and quantitative fracture analyses of high‐strength ceramics

The aims of this study were to assess the applicability and repeatability of qualitative and quantitative analyses of the fracture patterns of four different high-strength ceramics. Ten bar-shaped specimens of four high-strength ceramics with different material composition and fabrication methods had been fractured by three-point bending in water (n = 40). Commonly used fractographic patterns for brittle materials, such as mirror and mist, were used to characterize and quantify the fractured surfaces of these specimens. The analyses were performed twice, on separate occasions, by the same operator. Assessment of the association between fractographic patterns and fracture stress was carried out, and repeatability assessments of the measurements were performed. The fracture initiator site and the common fractographic markers surrounding this site were found in all specimens. Statistically significant correlations were found between certain fracture patterns and stress at fracture. The repeatability of the measurements of the different fractographic patterns varied among the materials. Fracture analyses seem applicable as a tool to determine the fracture initiation site and to estimate the force vectors involved in the fracture of dental high-strength ceramics.

Lead and cadmium in primary teeth from Illinois, USA

It has been shown that primary teeth may be used as indicators of lead and cadmium exposure in children. Two‐hundred‐and‐twenty‐seven primary teeth from Illinois, mainly from Chicago and surrounding areas, were analysed for their content of lead and cadmium by atomic absorption spectrophotometry. The lead and cadmium values from Chicago were significantly higher than the corresponding values in the various surrounding districts and in the rest of the material as a whole. Significant correlations between lead and cadmium were found for the whole material, for the city of Chicago, and for the material outside Chicago. Effects of the age of the housing and of urbanization were found for lead. A small effect of the age of the housing was found for cadmium. The authors conclude that further research is needed.