Accumulation of Amalgam Derived Mercury in the CNS
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Uncharged mercury ions will be oxidised in the blood and, although this process is rapid, it is not immediate. This is ample time for circulation and transport across the blood brain barrier. Once inside the CNS it will be oxidised to Hg2+ and in this form cannot escape back across the blood brain barrier. This is one of the mechanisms by which mercury is locked into the CNS. To suggest that mercury vapour does not readily pass into the CNS is incorrect. It is well documented that CNS is one of the main target organs for both mercury vapour and inorganic mercury.
Three mechanisms are known by which mercury is transported into the CNS:
a) Inhaled mercury is absorbed from the lungs and into the blood, by which route it is transported throughout the body and across the blood brain barrier. (53,54,55,56) .
b) Stortebecker and others (43) have demonstrated that mercury vapour in the oral cavity will adhere to the oro-nasal mucosa and pass directly through the bone at the base of the skull to enter the brain.
c) Some mercury from amalgams will be transported through the tooth and also from the oral mucosa, and undergo retrograde axonal transport back to the brain. Transport along nerve fibres has been shown to be at a rate of approximately 10mm per day (58,59,60) .