Rune Eide

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.

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.

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

Abstract 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 = 0.015), 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.

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.

Abstract 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

Abstract 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.

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.

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.

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.

Blood mercury following DMPS administration to subjects with and without dental amalgam

The use of DMPS as a diagnostic tool in patients with symptoms allegedly caused by mercury from dental amalgam fillings is disputed. We have previously shown that the mercury concentrations in urine cannot be used in such a way. In the present study, we wished to evaluate the effect on blood mercury levels (B-Hg) following intravenously injected DMPS in four groups of subjects: 19 controls without amalgam experience; 21 healthy controls with amalgam fillings; 20 patients with self-reported symptoms from existing dental amalgams; and 20 patients who had removed amalgam fillings. A single dose of DMPS (2 mg/kg) was injected. Blood samples were collected prior to the injection and after 15, 30, 120 min, and after 24 h, and mercury was analyzed by cold vapor atomic absorption spectrophotometry. All groups showed an initial drop of 24 to 30% in the blood levels, approaching baseline values (2.5-5.5 microg/l) after 2 h. The subjects with no amalgam experience had the lowest mercury values. There was no significant difference between the three groups with such experience. There were no significant differences between the two groups with amalgam fillings present. Patients with symptoms allegedly caused by amalgam were not different from the control groups. There were indications that part of the urinary mercury excreted during the first 30 min originated from blood.