I don't know the answers to your questions but I am going to forward them to a person I know that is very familiar with Boron. When I receive her answer, I will let you know.
Okay, I have your answer already.
Not a chemist but as I understand it heat / cold has no effect. Boron neutralizes fluoride with or without heat.. Finding true research on it is very difficult because of the ban that has been placed over it by WHO so it is worldwide not just United States. We do use it in our detox baths to neutralize fluoride and provide boron.