I think glass ionomers are extremely toxic. I had 4 spots of glass ionomers in my mouth. 2 7 years from cement for a bridge, one 2 years and another one was a somewhat open filling for 1 year, and I started gradually this year getting very sick. It was very difficult to find out why. Constipation, weight gain(everytime I tried to loose weight got very stomach sick), agressive attacks, cry fits, a miscarriage. It turns out it is fluoride poisoning. When you go to the doctor it is called fibromyalgia. What a hoax
Now I just need to remove one more glass ionomer. And I am getting much better finally.And I had far more problems than with the mercury, with which I also had problems by the way. In any case no doctor likes to treat you for fluoride poisoning, so think again about the glass ionomer. I do not wish anyone the same. Since I realised what was happening I already lost almost 20 lbs. In case your son gets problems, you can grab to calcium carbonate and magnesium supplements for relieve, but they will not go away until the last piece is gone.