My male Lab has never chewed anything up.
You might ask how I trained for such behavior.
Actually, I had nothing to do with it. I have a FM CBR who is a month older than my Lab. Anytime the lab would begin to chew on something, the Chessie would walk over and take the object away, she would not chew on it herself, she just didn't want the lab to have it. If he tried to take it back, which I only witnessed twice, she would chew on him.
Therefore, I probably have one of the few Labs whos' never chewed anything up.