What past problems have been solved by any forms of synthesis or amalgamation)?

I am not sure if this is on the path you are looking for, but modern day dentistry has discovered that the removal of decay replaced with an "amalgam" filling is the strongest, longest lasting tooth replacement material. All medical prescriptions are amalgamations, so in truth you could say that the majority of diseases and medical conditions are resolved or in remission because of the products of amalgamation.