Dental amalgam and selenium in blood.

It has been suggested that selenium (Se) exhibits protective effects against mercury (Hg) toxicity in humans due to formation of a Hg-Se complex bound to selenoprotein P in blood. The aim of the present study was to investigate Se concentrations in persons who had been examined with respect to general health problems associated with dental amalgam fillings. The Se concentrations were determined in whole-blood samples of 80 individuals by hydride generation atomic absorption spectrometry. The subjects comprised two main groups: 21 healthy controls with amalgam fillings and 20 patients who claimed symptoms from existing amalgam fillings. The median concentration of Se in blood (119.2 microg/L) was statistically significantly lower in subjects who claimed symptoms of mercury amalgam illness than in healthy subjects with amalgam (130.3 microg/L). The difference was more evident in individuals with more than 35 amalgam surfaces (P=0.003). Additional control groups without amalgam fillings comprised 19 healthy controls without amalgam experience and 20 subjects who have had amalgam fillings removed due to suspected symptoms associated with amalgam. The Se concentrations in these groups were not different from those with amalgam. It is indicated that persons with ill health self-related to dental amalgam might have a Se metabolism different from that of healthy people.

Neuron loss in cerebellar cortex of rats exposed to mercury vapor: a stereological study.

Mercury vapor produces tremor in humans and experimental animals. We have previously reported that mercury vapor intoxication over an 8-week period induces only subtle changes in dorsal root ganglia and nerve roots in rats. In the present study we have carried out stereological analyses of the cerebellum of the same rats, and demonstrated significant losses of Purkinje cells (12.7%, 2P = 0.005) and granule cells (15.6%, 2P = 0.016). All sizes of Purkinje cells were lost with an equal probability, i.e. there were no indication of any preferential loss of any subpopulation of the neurons. The volume of the granular cell layer was significantly reduced (18.9%, 2P = 0.0 15), whereas the volumes of the molecular layer and the white matter were unchanged. Previous stereological studies have demonstrated that methyl mercury intoxication primarily induces degeneration in the peripheral nervous system, while sparing the cerebellum. We therefore suggest that metallic mercury vapor and methyl mercury have different toxicological profiles in rats, where metallic mercury vapor mainly affects the central nervous system and methyl mercury mainly affects the peripheral nervous system.

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.

Diagnostic value of a chelating agent in patients with symptoms allegedly caused by amalgam fillings.

The chelating agent 2,3 dimercaptopropane-1-sulfonate (DMPS) has been used in a mercury mobilization test for diagnoses in illnesses allegedly associated with the presence of amalgam restorations. DMPS is an accepted antidote to heavy metal poisoning. The aim of the present study was to evaluate the diagnostic value of DMPS in patients with symptoms self-related to their amalgam fillings. The subjects consisted of four groups: 19 healthy controls without amalgam experience; 21 healthy controls with amalgam fillings; 20 patients who claimed symptoms of "mercury poisoning" from dental amalgam; and 20 patients who had amalgam fillings removed because of such symptoms. DMPS (2 mg/kg body weight) was injected intravenously, and urine was collected prior to the injection, 30 and 120 min after the injection, and throughout the next 22 hrs. The samples were analyzed for total mercury by cold vapor atomic absorption spectrophotometry. The total median amounts of mercury excreted over 24 hrs for those with complaints allegedly associated with amalgam and for the healthy controls with amalgam fillings were similar. Persons with amalgam fillings excreted about three times more mercury than those without. The controls, who had never had amalgam fillings, and the subjects who had had their fillings removed excreted median amounts of 8.5 microg and 7.2 microg mercury, respectively. The present DMPS challenge test did not differentiate between patients with or those without complaints self-related to their amalgam fillings but did confirm the higher mercury values in patients with dental amalgam.

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.

Mercury and silver in saliva from subjects with symptoms self-related to amalgam fillings.

The amount of mercury released into saliva from dental amalgam fillings is currently being debated. Mercury enters saliva as vapor, ions and particles of amalgam. The aim of the present study was to determine mercury and silver concentrations in saliva of persons with amalgam fillings. Moreover, it was the aim to investigate whether amalgam particles were present in samples of stimulated saliva in control subjects. In that case, we also wanted to determine the influence of these particles on the mercury concentrations found. Fifty-three patients with a wide range of complaints self-related to their amalgam fillings were examined by the Dental Biomaterials Adverse Reaction Unit of Norway. Among other tests, stimulated saliva was collected from each patient and analyzed for mercury and silver. Mercury and silver correlated with the amount of amalgam present. There was a strong correlation between mercury and silver concentrations. Amalgam particles were found by energy dispersive X-ray analysis. It appears that a considerable part of the mercury and silver were present as amalgam particles. The present study shows that amalgam particles in saliva have to be controlled for when analyzing mercury in saliva from subjects with amalgam fillings.

A stereological study of dorsal root ganglion cells and nerve root fibers from rats exposed to mercury vapor.

Although mercury vapor is known to produce tremor and peripheral neuropathy, neuropathological studies of the effects of the vapor are few in number. The aim of the present study has been to evaluate the effect of mercury vapor on the morphology of the dorsal root ganglion and the spinal nerve roots. Adult male rats were exposed to mercury vapor for 33 days. The exposed rats developed somatic signs of intoxication and became increasingly irritable. The total numbers and volumes of A- and B-cell perikarya in the dorsal root ganglia, the total number of myelinated axons in the roots, and the cross-sectional areas of axon and myelin in the nerve roots were estimated using unbiased stereological principles. The mean cross-sectional area of myelin associated with nerve fibers in dorsal nerve roots of the exposed group was significantly reduced by 20% (2P=0.014). A tendency towards a reduction was seen in axon area of myelinated nerve fibers in the dorsal nerve roots (2P=0.087) and in the total numbers and mean volume of A-cell perikarya (2P = 0.059 and 2P=0.087, respectively). No differences between the two test groups were found for any of the parameters measured in B-cells and ventral nerve roots. It is concluded that mercury vapor, in a dose sufficient to produce intoxication, induces only minor changes in dorsal root ganglion and nerve roots in rats.

The effect of selenium on the localization of autometallographic mercury in dorsal root ganglia of rats.

The autometallographic technique was used to demonstrate the localization of mercury in dorsal root ganglia of adult Wistar rats. The animals were either exposed to mercury vapour, 100 micrograms Hg m-3, 6 h day-1, 5 days per week, or treated with organic mercury in the drinking water, 20 mg CH3HgCl per litre, for 4 weeks. The effect of orally administered sodium selenite on the pattern of intracellular distribution of mercury in these two situations was investigated. In rats exposed to mercury vapour alone, faint staining was present in ganglion cells. The selenite induced a conspicuous increase in the number of stained cells and in the intracellular staining intensity. In rats treated with organic mercury, mercury deposits were detected within ganglion cells and macrophages. The number of mercury-containing cells was increased by co-administration of selenite. In addition, satellite cells, the capsule and vessel walls were faintly stained. Twenty weeks after cessation of the organic mercury treatment, mercury staining was reduced. Again, selenite treatment enhanced staining intensity. When studied using the electron microscope, mercury was restricted to lysosomes, irrespective of treatments. The present study shows that the deposition of autometallographic mercury in the dorsal root ganglia depends on the chemical type of mercury, the co-administration of selenite and the length of the survival period.

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.

Mercury content in rat teeth after administration of organic and inorganic mercury. The effects of interrupted exposure and of selenite.

Rat molars are indicators of exposure concentration and target organ content in chronic mercury vapor exposure. We wished to study the accumulation and persistence of organic and inorganic mercury in rat teeth and the effect of selenium on mercury retention. Male Wistar rats received either inorganic or organic mercury (with or without addition of selenite), selenite only, or no mercury or selenite (controls) in the drinking water for 4 weeks. Group A was killed after exposure. Group B was killed 20 weeks later. The mercury content was measured by cold-vapor atomic absorption spectrophotometry. The mercury content in the molars in group B was 66% and 77% less than in group A after inorganic and organic exposure, respectively. In the incisors the corresponding reductions were 90% and 97%. Selenite had limited effect on mercury retention in group A and none in group B. We suggest that rat molars and, by inference, human deciduous teeth may serve as indicators of organic and inorganic mercury exposure.

Autometallographic demonstration of mercury in rat molars.

Male, adult Wistar rats were exposed to 500 micrograms/m3 mercury vapor 6 h per day, 5 days a week for 4 wk. They were subsequently killed by transcardial perfusion. The molars were extracted, demineralized, and embedded in resin before sectioning. Autometallographic development was performed according to the method of Danscher & Möller-Madsen. Mercury deposits were found in small amounts in several areas of the pulp, but with larger accumulations of grains in relation to odontoblasts. Mercury also could be seen in odontoblastic processes in the dentin and predentin. Our conclusion is therefore that systemic uptake of mercury vapor leads to accumulation of mercury in the odontoblasts and that the mercury may be transported into the dentin tubules in the odontoblastic process.

Detection of mercury in rat spinal cord and dorsal root ganglia after exposure to mercury vapor.

Adult male Wistar rats were exposed to mercury vapor, 50 micrograms Hg/m3, 6 hr/day, 5 days/week, over 1-, 2-, 3-, 4-, 6-, and 8-week periods. Sections from the spinal cord and dorsal root ganglia from spinal levels C1, C5, T6, and L1 were stained with the autometallographical technique and the distribution of mercury deposits described at light and electron microscopical levels. A quantitative analysis of the amount of mercury in blocks of the spinal cord was performed using cold vapor atomic absorption spectrophotometry. After an exposure period of 2 weeks, silver-enhanced mercury grains could be observed in spinal cord neurons located in Rexed laminae IV-X. Ventral horn motoneurons were heavily stained in all of the spinal cord segments. Ependymal cells and glial cells of both the spinal gray and white matter contained cytoplasmatic mercury accumulations in rats exposed to mercury vapor for 4 weeks. In the dorsal root ganglia, only ganglion cells showed a faint mercury staining and the amount of staining was notably less than that seen in the ventral horn motoneurons. At the ultrastructural level, mercury was seen primarily within lysosomes of target cells. The quantitative mercury measurements demonstrated that spinal cords from rats exposed to mercury vapor for 6 or 8 weeks contained a significantly higher concentration of mercury than those from control animals.

Mercury contents of indicators and target organs in rats after long-term, low-level, mercury vapor exposure.

Five groups of Wistar rats received graded concentrations of mercury vapor from 10 to 100 micrograms Hg/m3 6 hr, 5 days a week, from 4 to 11 weeks of age. One group breathing ambient air served as controls. The mercury levels of the indicators blood, hair, molars, and incisors as well as the target organs kidney cortex, cerebrum, cerebellum, liver, lung, spleen, tongue, and femur were measured by cold-vapor atomic absorption spectrophotometry. The mercury vapor had no negative influence on the weight gain of the animals. The results showed that the kidney cortex had the highest concentration of mercury. The mercury contents of all the indicators and all the target organs, with the exception of femur, were positively and significantly correlated with the exposure concentration. The rat molars had the highest correlation coefficient with the kidney mercury values, but no indicator had a significant correlation with all target organs. Rat molars are to some degree comparable to human deciduous teeth regarding time of mineralization and eruption. Based on the results presented in this study, we tentatively suggest that human deciduous teeth can be useful indicators of chronic mercury exposure not only at the exposure concentration level, but also as indicators of the mercury uptake in organs such as kidney and cerebrum.

Mercury in primary teeth in preindustrial Norway.

Seventy-nine primary (deciduous) teeth were excavated in 1978 underneath the floor of the stave church in Uvdal, Buskerud County, Norway. The mercury content of 57 teeth was measured by means of cold vapor atomic absorption spectrophotometry. As a comparison, 124 primary teeth from modern Norway were analyzed. A significant statistical difference was found between the two sets of material. In the Uvdal material a correlation was found between the mercury and copper contents. For the modern material a correlation was found between mercury and lead, and between mercury and zinc. The authors maintain that the values found for the Uvdal material represent base-line values for mercury in primary teeth, and probably reflect uptake from natural environmental sources only. Furthermore, these values may be used for reference in studies of other preindustrial, as well as modern, primary teeth. Our findings also indicate a higher level of mercury in modern than in preindustrial primary teeth in Norway.

Numerical density and distributional pattern of dentin tubules.

By a new method the numerical density and distributional pattern of transversely cut dentin tubules and the diameters of their peritubular dentin walls were measured in sections near the dentin-enamel junction (DEJ), midway to the pulp, and near the pulp wall in human premolars. For each section the mean and standard deviation of these variables were expressed. At all three levels the measurements comprised the same bundle of tubules from the DEJ to pulp in the coronal dentin. The number of tubules per square millimeter increased more than three times, and the diameters of peritubular dentin decreased one-tenth, whereas central distances between tubules were halved from DEJ to pulp. Thus the pulpward reduction of intertubular dentin is quantified. The distribution of the tubules is not regularly hexagonal, but the distances between them at each given depth are still very uniform in all directions. The pattern of cross-cut tubules often showed distinct short curved rows. The quantitative method might be used to determine taxonomic affinities.

Survey of mental health of foreign students.

The multifaceted nature of problems foreign students face have led some researchers to conclude that these students tend to suffer from poor health during their overseas sojourn. This assertion is examined among foreign students at the University of Bergen by means of a questionnaire survey. Loneliness, tiredness, sadness and worrying were reported as a frequent source of problem by nearly one in four of over 300 respondents. Students reported a decline in their general state of health as well as a rise in the occurrence of syndrome-like tendencies resembling paranoia, anxiety, depression and somatic complaints. These tendencies were attributed to certain psychosocial factors such as information received regarding study opportunities, social contacts with other tenants in the hall of residence and future job opportunities. Scandinavian students on the whole tended to have better mental health than students from the other countries. The implications of impaired health among foreign students is discussed.

Finishing and polishing glass-ionomer cements.

Four different methods for finishing and polishing the surfaces of two different glass-ionomer cements were studied by measuring the roughness of specimens at different stages of the procedures. Method 1 consisted of the four 3M Sof-Lex XT discs. Method 2 included a round, fine-grit diamond and the Vivadent polisher. In method 3 a round Arkansas stone and the Vivadent polisher were used. Method 4 comprised medium and fine sand and fine cuttle paper discs. Petroleum jelly was always used, to prevent heating and desiccation of the specimens. The cements used were KetacFil and KetacSilver. The smoothest surface was found after removal of the strip. The Sof-Lex medium disc gave the least rough surface for KetacFil, whereas the fine cuttle disc gave the smoothest finish for KetacSilver. Discs in sequence are to be preferred to diamonds and stones.

A simple system for generating low-dosage mercury vapor for animal experiments.

A system using unlabeled, metallic mercury for generating low-dosage vapor for animal experiments is described. The system consists of four acrylic plastic chambers: one chamber containing the mercury source, one for mixing the mercury vapor with air, one exposure chamber, and one containing activated coal filters and mechanisms for regulating the airflow. The chambers are connected to each other by means of 80-mm-diameter polyvinyl chloride tubes reinforced with wire. Additional control and supporting equipment is also used. The system is easy to set up and requires minimal attendance during use. A standard deviation of 3-4% in the mercury vapor level during 6 h of exposure is typical. The conditions for the animals during exposure and the safety for the personnel during use are optimal.

Finishing and polishing of composites.

Four different methods for finishing and polishing the surfaces of two different composite materials were studied by measuring the roughness of specimens at different stages of the procedures. Method 1 consisted of four different Shofu SuperSnap discs. Method 2 included the Shofu Dura-White stone, the Shofu CompoSite point, and the Vivadent polisher for composite resins. In method 3 the four 3M Sof-Lex XT discs were used. Method 4 comprised a green stone, a carbide finishing bur, and the Vivadent polisher for composite. All four methods were completed by using Kerr Command Ultrafine Lustre Paste. The composites used were Silux and P30. After the initial finishing, all four methods gave significant effect when used on the Silux, but on the P30 only methods 2, 3, and 4 gave a significant improvement. However, the degree of effectiveness of the methods varied greatly.