|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1993 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1992 : ¥1,600,000 (Direct Cost : ¥1,600,000)
This study was carried out to obtain information regarding the accumulation and influence of mercury released from dental amalgam in a livin body. To address this object we have employed an experimental animal model in which pregant rat received amalgam tooth fillings. We measured a total mercury in organs and blood samples of mother and their fetus. The results obatined in this study were summarized as follows.
Experiment 1.Mercury from dental amalgam appeared in maternal and fetal organs after amalgam tooth restorations in the mother rtas. In mothers, the mercury concentrations of the brains, livers, kidneys and placentas from the experimental group were significantly higher than those of the controls, and the highest mercury was found in the kidneys, followed by placenta, liver and brain. In fetuses, the mercury concentrations of the brain, liver from the experimental group were significantly higher than those of the controls. The highest mercury concentration among fetal organs was
found in liver, followed by kidneys and brain.
Experiment 2.With the increasing number of amalgam fillings, mercury concentrations in organs of mother and their fetuses tended to increase, while body weight of fetus tended to decrease.
Experiment 3.In order to examine the influence of amalgam fillings on growth of fetuses, 4 teeth were fillied with the glass ionomer cement instead of amalgam. In mothers, growth curves of the experimental animals was lower than that of the control animals. Intake of the diet and water were significantly lower than those of the controls at the early pregnant stage. Althogh, significant difference was not observed, body weight of the fetus was lower than that of the controls. These results indicated that dental treatment itself seemed to influence the intake of the diet and water at the early pregnant stage and to slow the growth of mother rats and their fetuses. These findings of this study and the results of the experiment 2 suggested that it was likely that amalgam fillings themselves did not influence the growth of fetuses.
Experiment 4.This study was carried out to examine the relation between amalgam fillings in pregnant rats and marcury concentrations in organs of offspring's of second and third generations. The mercury contents in the brain, liver, kidney and spleen of the experimental animals of the second generation were higher than those of the controls, although significant differences were not observed. In the third generation, mercury concentrations were almost the same between experimental and control groups.
Experiment 5.This expriment was carried out to examine the chemical form of mercury accumulated in organs of mother rats and their fetuses. In mothers, the mercury contents in the whole blood, erythrocyte and plasma of the experimental animals were significantly higher than those of the controls. In fetuses, the mercury contents in the whole blood of the experimental animals were significantly higher than that of the controls. Fetus to mother ratio, and Erythrocyte and plasma ratio of the experimental animals were lower than those of the controls. On the other hand, PF ratio of the experimental group was higher than that of the control group. Chemical transformation of elemental mercury after introduction into fetuses remains unclear, though it is suggested that elemental mercury undergoes an oxidation process similar to that occurring in maternal animals. Ratios of mercury concentrations in erythrocytes and plasma depend upon the chemical forms of mercury compounds ; after mercury exposure to mercury vapor, more mercury is found in red cells than in the plasma, but after inorganic mercury exposure, the reverse is true. In this experiment, the erythrocyte to plasma ratio of mothers of the experimental group was significantly lower than that of the control group. This indicates that the chemical form existing in the blood stream is possibly inorganic. In the fetal organs, blood returning from the placenta through the umbilical veins enters fetal circulation through the ductus venosus, mainly by passing through the liver. Furthermore, it is known that catalase has a great capacity to oxidized mercury vapor into ionic mercury and that this enzyme is contained abundantly in liver. The chemical form of mercury passing through the placental barrier is possibly elemental. Although we could not examined the mercury concentration ratio of erythrocytes and plasma in the blood sample of the fetus, mercury in the fetal circulation system is possibly inorganic because the highest mercury accumulation was found in the liver. Consequently, it is most likely that part of the mercury released from the dental amalgam filling passing the placenta is oxidized into ionic mercury in fetal liver and accumulates in that organ. Less