Hi Jeannie,
I haven't heard of this symptom in GD but people with Graves' disease often have chemical sensitivities and hypersensitivity reactions. I once had a reaction to something in a filling and my mouth erupted in blisters. It was at a time when antibiotics were added to fillings and later I was found to have a penicillin reaction. I've had a few weird experiences like that in my many, many dentist visits.
Since your symptoms went away after the fillings were removed, it's even more suspect that your reaction was to something in the fillings. Your sister may also be having a similar hypersensitivity reaction but may not develop Graves' disease. Best, Elaine