A dog biting, mouthing or otherwise putting his teeth on someone can be a sign of disrespect. He wants your attention and he will get it, just as he would if he was pushing around a member of his pack. First try letting out a very loud, deep, OUCH to break him out of that behavior then ignore him. No eye contact, talking, etc. He is a piece or furniture to you at that point. If the "ouch" doesn't do it get an air horn, hide it in your pocket and when your dog puts his teeth on you blow it as he does. This has worked for me and several friends with dominant dogs. Usually within a few episodes. I believe you should hide it from him because he will quickly figure out he can put his teeth on you if you don't have it in your hand. Reward and praise when he greets you without jumping.
