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In 29 volunteers with a low amalgam load, the number of amalgam-covered tooth surfaces and the occlusal area of the fillings were determined. Concentrations of total mercury were measured in plasma and erythrocytes as well as in urine together with the excretion rate. Absorbed daily doses were estimated from intraoral Hg emission by two separate methods. The transfer of Hg from the fillings via the oral cavity and blood to urinary excretion was evaluated according to the most representative combination of parameters. This consisted of urinary excretion (1), Hg concentration in plasma (2), absorbed dose (3), and occlusal area (4). Pairwise correlation coefficients were 0.75 for parameters 1 vs 2 and 2 vs 3 and 0.49 for parameters 3 vs 4. Within 9 days after removal of the fillings, a transient increase was observed in plasma Hg levels only. This was reduced in those volunteers to whom a rubber dam had been applied during removal. Peak plasma Hg was 0.6 ng/ml on average and decreased with halftimes between 5 and 13 days. A significant decrease in Hg excretion was noted not before 100 days after removal. Being relatively insensitive to dietary mercury, the determination of total mercury in plasma and of its urinary excretion rate appears, under practical aspects, most suitable for the investigation of Hg uptake from amalgam.

Investigators established methods for the analysis of total mercury (Hg-total), oxidized mercury and mercury bound to sulfhydryl groups (Hg-S), mercury vapor (Hg0), and mercury from amalgam particles (APs) in fecal samples. Two individuals consumed mercury as a mercury-cysteine complex mercury vapor, and mercury from amalgam particles, and the cumulative excretion of mercury in feces was followed. Investigators found that 80% of the mercury from amalgam particles and mercury bound to sulfhydryl groups was excreted, but only 40% of the mercury vapor was excreted. Speciation of mercury excreted in feces from 6 individuals with a moderate loading of amalgam fillings showed that most of the mercury originating from the fillings consisted of oxidized mercury, which was probably bound to sulfhydryl-containing compounds. The proportion of amalgam particles in fecal samples from these individuals was low, and it did not exceed 26% of the total amount of mercury excreted.

From 1972-1993 (5 years internship and 16 years of my own practice) amalgam was by far the most prevalent dental filling material used by me (in the side tooth area). Different reasons led me to abandon use of this material in the spring of 1994. An amalgam-critical work which had appeared in the FASEB journal in 1989 (Hahn et al.) was certainly an important reason for my decision. Moreover, some of my own earlier observations (e.g. with Pat. No 2 and Pat. No 73) and the fact that alternatives to amalgam were widely available, were equally important reasons for me to discontinue using amalgam, a material I had considered highly reliable before.

With present knowledge it is impossible to estimate the risk of effects on the foetal brain induced by the mother’s exposure to mercury from amalgam. Available facts, however, do not support a dismissal of the risk. Therefore treatment of children and women of childbearing age with amalgam should be avoided. It is also recommended that use of amalgam for dental restorations in the population in general is abandoned and substituted with less toxic material, whenever this is available and affordable.

Seven multiple sclerosis subjects had their silver dental fillings (amalgams) removed which contained approximately 50% mercury. A visual evoked response (VER) test was performed before amalgam removal. Approximately six months after amalgam removal a second VER test was performed on all subjects, and the latencies of the VER decreased significantly. The mean latency of P1 for the right and left eye combined decreased by 23.1 milliseconds (P = 0.011) and N1 for the right and left eye combined decreased by 23.1 milliseconds (P = 0.026). It was hypothesized that mercury from dental amalgam was an etiological factor in reduced nerve conduction velocity in MS subjects.

Seven female subjects diagnosed with mulitple sclerosis were tested for hearing at threshhold frequencies of 250, 500, 1000, 4000 and 8000 Hz. The subjects then had their silver dental fillings (amalgams) removed. Between six and eight months after amalgam removal, testing for hearing was repeated. Six of the seven subjects showed improvement in hearing of the right ear and five of the seven showed improvement in the left ear. Four of the six frequencies tested in the right ear improved significantly and three of six improved significantly in the left ear. The total frequencies were averaged before amalgam removal and compared to after amalgam removal. Hearing improved an average of 8 db (p=0.02).

RESULTS:
After removal of all amalgam restorations, only the non-rubber dam group showed significant increases in the mercury levels found in plasma (p = 0.012) and urine (p = 0.037). However, one year later, the mercury levels in plasma and urine had sunk significantly below the pre-removal levels for both groups. When the changes in the mercury levels found were compared between the groups, the non-rubber dam group showed a significantly higher increase of mercury in plasma than the rubber dam group the day after removal (p = 0.0010). Compared to the pre-removal mercury levels in plasma and urine, the levels found 1 y after removal of all amalgam restorations were on average 52 +/- 23% (range 4-89%) lower in plasma and 76 +/- 21% (range 20-94%) lower in urine.

SIGNIFICANCE:
The study showed that dental amalgam had a statistically significant impact on the mercury levels found in plasma and urine in the patients tested, and that the use of a rubber dam during removal of all amalgam restorations significantly reduced the peak of mercury in plasma following removal.