Pet Myths: A dogs mouth is cleaner than a humans

I'm not sure where/how this one got started but I hear this a couple of times a month. I hear these voices, asserting with absolute certainty that it is a proven fact that a dogs mouth is cleaner than a humans, every time I catch one of my bulldogs eating some steaming fetid mass on our property before I run after them and rinse their mouth out. 

I'd like to find one human, just one, that could watch a dog eat a 1/4lb scat burger left by the local fox or bobcat and tell me that, yes, I'd let my dog kiss me goodnight. As someone once said, "A dogs tongue is an all purpose tool: washcloth, scrubber, toilet paper" Basically a dog isn't terribly choosy about where they stick their tongue and what they will eat. As an example, I give you Big Tuna, our youngest English Bulldog with a voracious appetite. She won't turn down any meal, no matter how long it has been dead and baking in the sun. I recall on one occasion (yes, this scared me for life) I caught her staring at me, a somewhat guilty look on her face. Then I noticed something sticking out of her mouth. I proceeded to grab the object and engaged her in a brief tug of war (she's wasn't going to give it up easily which is always a warning sign) before removing something that was approximately two to three inches long. Upon closer inspection, I realized that it was the atrophied remains of a squirrels arm, complete with dried skin, radius, ulna, etc. Obviously the hawks didn't finish their meal or dropped the offensive limb from a pine tree ( I don't believe it was an unusually aggressive rare meat eating orchid either). Yes, there are even more disgusting stories that I can regale you with but I'll save those. 

So back to the ever elusive point I was originally trying to make: a dogs mouth is not cleaner than a humans mouth.