It is probably teething. I learned the hard way by having EVERY SINGLE one of my pair of shoes demolished by my Chihuahua during his teething phase...I suggest you provide alot of toys and chewies for your doggy and watch for any teeth that might pop out on your floor
I think its so cute when that happens.
If the drooling doesn't stop though I'd look into it, although I don't know that much about teething to be honest. Hopefully someone else will give you a little more insight