NFL's Von Miller -- Grillin' Out Again ... Drops $57k On Mouthpiece

NFL superstar Von Miller just can't leave his mouth alone ... cause the SB MVP has copped yet another INSANE custom grill ... and TMZ Sports has pics of the $57k creation.

We kinda knew it was gonna happen ... when Miller hit up celebrity jeweler Johnny Dang to cop his 1st grill -- a $40k monster -- back in March we were told a 2nd was already in the works.

The new one's here now ... and it's crushing the starter piece, featuring yellow 18kt gold, VVS princess and baguette cut diamonds and boasting a $57k price tag ... nearly 20k more than the original.

We asked Dang why Von was so quick to grab another piece of bling, and he told us, "Because it is one of a kind ... no one has a grill like that."

Translation -- SWAG.