"A dog's mouth contains a lot of bacteria," confirms Dr. Gary Clemons, a veterinarian in Milford, Ohio. "Remember, a dog's tongue is not only his wash cloth but also his toilet paper."
'''If you don't mind my falling back on a gut feeling, I'll conclude by reiterating that I have personally witnessed a human being allowing a dog to lick the inside of his mouth, and it was... unpleasant to behold. Say what you will about the relative cleanliness of the canine mouth vs. the human, I'd rather be French-kissed by a human being than a dog any day. I'm just fussy that way'''
http://urbanlegends.about.com/od/dogs/a/dog_breath.htm
Is a dog's Mouth Cleaner than a Human's?
Very interesting reading.....esp for a rainy day.