i'm not too sure, but my uncles dog used to bite me playfully when he was a puppy, then when i next saw him 3 years later, he full on attacked my face (luckily moved and got a couple of scratches on nose and cheek, but took a nasty gash in the wrist when i covered my face)! i think he was trying to be playful again...i do actually love dogs though, so let us know how it goes will you?