Why do astronauts get all the good words, like space shuttle and EVA (extra-vehicular activity or spacewalk) and Tang? Did I say Tang? Yes indeed. And I got stuck with words like gums and molars and amalgam.
I mention Tang because amalgam filling material was first used in the T’ang dynasty in China around the 700’s a.d. and first introduced to the U.S. in 1833. Some people still refer to it as “lead fillings” because of the color it turns when it corrodes. Amalgam is made of 50% mercury and a 50% powder mix comprised of silver, tin and copper. All of those metals are necessary to make amalgam do what it does, turning from a gel when first mixed to a hard alloy after several hours.
Table salt also known as sodium chloride is required by the human body. But if we were to break sodium chloride down into its 2 components the metal sodium could burn holes through us just by touching it and the chlorine gas would kill us if we breathe it. In like manner it is the mercury in the amalgam filling which has always caused our health concerns. The American Dental Association has stated that mercury is of no health concern when it is combined with the other metals in a filling. What they fail to state is that not all the mercury in a filling combines completely with the other metals. There are always small wells of pure mercury spread throughout the hardened filling. Is there enough elemental mercury there to cause health problems? Now there is the million dollar question.
White composite fillings are successful because of the bonding process to make them physically attach to the tooth structure. Amalgams, on the other hand, are held in the cavity preparation by physical undercuts in the tooth. On a microscopic level the space that remains between the hardened amalgam and the prepared cavity is wide enough for the bacteria that causes tooth decay to walk side by side hand in hand (assuming bacteria have hands). The only reason cavities don’t occur immediately is that the black corrosion product of the tin/mercury alloy (called gamma 2) is anti-cariogenic – it inhibits tooth decay. The bad side effect of the gamma 2 is that it also contributes to a faster breakdown of the amalgam. So if you have old black corroded amalgams, be happy and sad at the same time. Because your teeth with those old fillings are more protected than the ones with the shiny silver. Although for not as long.
Lead fillings, Chlorine and Tang