Yoshifumi Takahashi

Release of mercury from dental amalgam fillings in pregnant rats and distribution of mercury in maternal and fetal tissues.

Mercury vapor released from a single amalgam restoration in pregnant rats and mercury concentrations in maternal and fetal rat tissues were studied. Dental treatment was given on day 2 of pregnancy. Mercury concentration in air sample drawn from the metabolism chamber with the rat was measured serially for 24 h on days 2, 8 and 15 of pregnancy. An average mercury concentration in the air samples from the rats given amalgam restorations was 678.6+/-167.5 ng/day on day 2. The average mercury concentration in the air samples tended to decline as time elapsed but a marked amount (423.2+/-121.5 ng/day) was observed even on day 15. The amount of mercury in the air samples increased 7--20-fold after chewing. The placement of the single amalgam restoration (3.8--5.5 mg in weight) increased the levels of mercury approximately three to 6 times in the maternal brain, liver, lung, placenta and 20 times in the kidneys. The highest mercury concentration among fetal organs was found in the liver, followed by the kidneys and brain. Mercury concentrations in maternal organs and fetal liver were significantly higher than those of the controls, and concentrations in maternal whole blood, erythrocytes and plasma, and in fetal whole blood were also significantly higher. Mercury concentrations in the fetal brain, liver, kidneys and whole blood were lower than those of the maternal tissues.

Placental transfer of mercury in pregnant rats which received dental amalgam restorations.

Mercury vapor released from one, two and four amalgam restorations in pregnant rats and mercury concentrations in maternal and fetal organs were studied. Dental treatment was given on day 2 of pregnancy. Mercury concentration in air samples drawn from each metabolism chamber with a rat were measured serially for 24 h on days 2, 8 and 15 of pregnancy. On each day of pregnancy, the amount of mercury in 24 h air samples was in proportion to the amalgam surface areas. Linear regression analysis showed relatively high correlation coefficients between the mercury content and amalgam surface areas, and the coefficients were statistically significant. A highly significant correlation was also found between the number of amalgam fillings and their surface areas. Mercury concentrations in major maternal organs with one, two and four amalgam fillings tended to increase with the increasing amalgam surface areas. Spearmans rank correlation test revealed significant correlations in the brain, liver, kidneys and placenta but not in the lung. Furthermore, significant correlations were also found between the mercury concentrations in all maternal organs and the amount of mercury in 24 h air samples on day 15 of pregnancy. Mercury concentrations in fetal brain, liver and kidneys were much lower than those of the dams but liver and kidneys showed positive correlations between the mercury content and maternal amalgam surface areas. Similar correlations were observed between the mercury concentrations in fetal organs and the amount of mercury in 24 h air samples on day 15 of pregnancy. In fetal brain, no significant correlations were found between either maternal amalgam surface areas or the amount of mercury in 24 h samples on day 15 of pregnancy but significant uptake of mercury was found in the samples from the dams given four amalgam fillings. The results of the present study demonstrated that mercury vapor released from the amalgam fillings in pregnant rats was distributed to maternal and fetal organs in dose-dependent amounts of the amalgam fillings.

Dissolution of metallic mercury in artificial saliva and eleven other solutions

Dissolution of metallic mercury immersed in various solutions for one, three, seven, and 14 days was investigated by flameless atomic absorption spectrophotometry. Solutions used in this study were artificial saliva, compounds of the four groups forming the artificial saliva (inorganic salts, amino acids, vitamins, other organic compounds) wholly or in part, 0.9% NaCl solution (saline solution), Ringers solution, and distilled water. Artificial saliva showed a level of mercury dissolution seven times higher than that of saline or Ringers solution. A large amount of dissolution, similar to that in artificial saliva, was found in the solution of the other organic compounds (containing glutathione) and in a solution containing only glutathione. Mercury dissolution in the solution of vitamins was small. There was a similarity in dissolution amounts between the solution of inorganic salts and that of amino acids. Glutathione played a major role in the dissolution of mercury.

A Study of Interface Bone and Microcirculation of Implants under Occlusion.

インプラント界面骨と微小循環について, 実験的にビーグル犬下顎骨にチタン・インプラント (ADSインプラント) を植立, 上部構造を装着して9カ月間咬合させた後, 主に骨付き微細血管鋳型法を用いて試料を作製, これを走査型電顕で観察した。その結果, インプラントと接する界面組織は骨ならびに小塊状の線維性結合組織であった。この小塊内には特異な分布形態・走行を示す毛細血管が小数分布し, この毛細血管と近接する界面骨には骨吸収窩 (ハウシップ窩) が観察された。これに対して血管の存在しない界面骨の表面には, ハウシップ窩は観察されなかった。いずれにせよ, インプラント界面全体に分布する毛細血管は極めて少なかった。一方, 界面骨の裏側, すなわち骨髄側には近接して特異な毛細血管網が密に分布する箇所があり, この部位の骨表面には無数のハウシップ窩が観察された。以上のことから, 界面骨の厚さは骨髄側でコントロールされ, 一度形成された界面骨の代謝活性は極めて低く, 環境変化に素早く対応することが出来ない状態にある, ということが微小循環の面から示唆された。