Great you've found this forum Ohno!
I've never had a TPA, but I'm amazed at the number of patients I see with one. I've only observed a small number being put in, and none have touched the roof of the patients mouth. The patients were told to expect it to be a week or two before they felt totally comfortable with the TPA, and during that time, to read outloud the Rainbow Passage as often as they could. Also to sing and recite from books. The orthodontists' recommended additional warm salt water rinses to help sooth their mouth.
Most patients appear to adjust well before their next appointments and report that they quickly forgot they have a TPA. Hope this also happens for you.
Take care!