Yeah, I've hear of this issue in danes. Luckily Gunther has been a dream. He only once started chewing on the couch, but he was caught in the act, so that stopped quickly. One other time he started chewing on the corner of the cupboards, but I think that was b/c his bed was there, and the cupboards were right where his head would be. I moved the bed, and no more chewing.
A friends' dane like to turn all the corners in her house into blunt curves, if you know what I mean. She ate walls.
I agree confining is the thing to do until he outgrows this.