Havent had pants made by Ambrosi but cant say enough good things about NSM pants. She makes a great, higher rise, comfortable pant. My first pair from Mina were a little too full at the bottom for me but that was easily corrected on subsequent pairs.
I think they are plastic. Most all I've seen in that style of button and used on the interior of the trouser are plastic. Could be something different that is available in Italy, no way to know from the picture.