MERCURY LEVELS IN PLASMA AND URINE AFTER REMOVAL OF ALL AMALGAM RESTORATIONS - THE EFFECT OF USING RUBBER DAMS

Objective. The aim of the present study was to determine whether remov al of all amalgam restorations might significantly affect mercury leve ls in plasma and urine and whether the use of rubber dams might reduce patient exposure to mercury during amalgam removal. Methods. All amal gam restorations were removed from 18 subjects during a single treatme nt session in which a rubber dam was used and from 10 subjects when a rubber dam was not used. All amalgam restorations were removed by the same dentist using high-speed cutting, water coolant, and high-volume evacuation. The levels of mercury in plasma and urine were analyzed bo th before and during the subsequent twelve months after amalgam remova l. In order to determine whether removal of all amalgam restorations m ight cause an exposure large enough to significantly increase the merc ury levels in two indicator media for mercury exposure, i.e., plasma a nd urine, and to determine if the removal might cause a significant de crease in the mercury levels found over time, the one-tailed, paired S tudents' t-test was used. For each individual, the pre-removal levels were compared with both the levels found in plasma on d 1 and in urine on d 10, and also with the levels found 1 y after removal. Furthermor e, in order to examine whether the use of rubber dams had any effect o n the mercury levels found after removal, the changes in the mercury l evels found were compared between the groups using the Wilcoxon-Mann-W hitney rank sum test. Results. After removal of all amalgam restoratio ns, 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 signi ficantly below the pre-removal levels for both groups. When the change s in the mercury levels found were compared between the groups, the no n-rubber dam group showed a significantly higher increase of mercury i n plasma than the rubber dam group the day after removal (p=0.0010). C ompared to the pre-removal mercury levels in plasma and urine, the lev els found 1 y after removal of all amalgam restorations were on averag e 52 +/- 23% (range 4 - 89%) lower in plasma and 76 +/- 21% (range 20 - 94%) lower in urine. Significance. The study showed that dental amal gam had a statistically significant impact on the mercury levels found in plasma and urine in the patients tested, and that the use of a rub ber dam during removal of all amalgam restorations significantly reduc ed the peak of mercury in plasma following removal.