My 4-1/2 month old Tibetan Spaniel mix puppy used to nip/bite a lot when i first got him a couple of months ago, but has been improving since the day we brought him home(nipping/biting less frequently, being more calm overall). However, just recently he began nipping alot more (as much if not more than when i first got him). I noticed that his puppy teeth were coming out (few loose teeth and a couple already fell out) and was wondering if that could be the cause of the increased biting. What steps should i take? I'm worried that he will continue this behavior and his improvement in behavior over the past couple of months has been reversed.