Thornton went after Orpik during a stoppage in play Dec. 7, slew-footing him to the ice and punching him twice. Orpik sustained a concussion and was taken off the ice on a stretcher. Earlier, Orpik hit Boston's Loui Eriksson, knocking him out of the game with a concussion.
Thornton was assessed a match penalty.
Orpik hasn't played since the game.
The suspension will cost Thornton $84,615. He served three games of the ban before the length of the suspension was determined.