How come a dog's mouth is cleaner than a human's?

To complete this test you will need access to certain supplies. However, take a swab of the inside of a dogs mouth and place it in a petri dish on top of a nutritional solution and do the same thing to yourself. Cover the petri dishes with their counterparts. Then incubate the petri dishes in a warm environment and wait 24 to 48 hours. Then remove the petri dishes and see how many more germ spots have grown on top of the nutritional solution.