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DENTAL AMALGAM & MERCURY POISONING of the amalgam metals, tance and stability of the amalgam materials A number of recent (1985) studies of dis- used for fillings will display variable rates similar metal corrosion showed that over a Of corrosion tolerance. Higher heat and 35 week period, mercury released from higher corrosion currents will entail a con- amalgams in contact with gold, ranged up to OMmitant increase in the vapourisation of 1650 micrograms per square cm of amalgam Mercury. Studies of the corrosion levels of surface. When different amalgams were in 4Mmalgam fillings of more than ten years age contact the amount of mercury released re ya br rey ey . Fi , -, pr ee ee mated that 240-560 milligrams of toxic mer- The real source of danger is not the cane wands bas beens relented chewing seer ‘ al years of the corrosion phase. mere presence of mercury in amal- Pl = gam fillings but the presence of two Fe al different metals in the mouth, such Pl: mame an extracted ieeth as mercury in amalgam and gold in ave shown that mercury migrates ray from amalgam fillings to root and other teeth, giving rise to an electro- : i ee galvanic current with the resultant jaw bone and can be enriched there. inflammatory reaction and the When there has been contact with release of mercury into the circula- gold, the level can reach more than tion® 'y = 1200ppm (parts per million, micro- = grams/gram tissue)... Such concen- al exposure limit of 25 micrograms/m’.* Exuded mercury vapour is not the only mechanism for mercury exposure in the oral cavity. Corrosion processes are also imper- ceptively occurring, continuously releasing small amounts of mercury. This takes place by a selective attack on the intermetallic compound with the highest half cell poten- tial, With conventional amalgam this is the gamma 2 phase which corrodes and releases tin and mercury ions.* Recently, S. Ayres has drawn attention to the findings of E.S. Lain in the early 1930s, that the electrolytic liberation of mercury from fillings is enhanced by the presence of more noble metals such as gold in the oral cavity.” Amalgam fillings in direct contact with the gold in bridges or in teeth adjacent to crowns are particularly susceptible of corro- sion. Since the gold serves as a cathode and the amalgam as an anode of a galvanic cell, the anodic process results in the dissolution Measurements on extracted teeth have shown that mercury migrates from amalgam fillings to root and jaw bone and can be enriched there. When there has been contact with gold, the level can reach more than 1200ppm (parts per million, micro- grams/gram tissue)... Such concen- trations must be regarded extremely toxic.” Given factors such as the nature of the amalgam, the age of the filling, degree of heat and electric current generated in the mouth, coupled with the acidity of certain foods and beverages, the corrosion resis- — NEXUS*65 JUNE-JULY 1992 Continued from page 19 There is yet another aspect of mercury Continued on page 66