human mouth
No, the human mouth is not clean. The human mouth is full of bacteria. It is a warm, wet, environment which is a great place for bacteria to grow. Brushing and using mouth wash can help eliminate some of this bacteria.
The human mouth is filled with good bacteria. This bacteria is necessary as it helps to break down food for digestion. Bad bacteria in the mouth comes from leftover food particles that fester if teeth are not brushed properly.
It maybe helpful because the bacteria in a human mouth is used to "clean" food, but since a dog pants constantly or what not. Their bacteria in their mouth is highly altered constantly keeping the dog's mouth free from harmful bacteria.
A dog's mouth is cleaner because it contains less bacteria although these bacteria are more harmful to humans
In your intestines, on your skin, in your mouth, etc
The bacteria share the same abiotic factors like human beings in order to survive, grow and flourish.
The human anus, or butt, is actually cleaner. The mouth excretes germs and bacteria of a more potent manner. But be aware of the fact that you are way more likely to get sick from having someone's anus in your mouth than having someone's spit in your mouth.
Yes. There are billions of different bacteria living inside your mouth. About 100,000 per tooth and millions on your tongue. The only way to get rid of harmful bacteria is wash your mouth daily and brush your teeth 3 times a day. Many of the bacteria is harmful that lives in your mouth so be careful what you put inside it because then it could multiply!
Actually, yes. Some truly nasty bacteria such as streptococcus (the bacteria that causes strep throat, among other things) is one of many that can be found on toilet seats. A dog's mouth on the other hand, can house colonies of bacteria. Now, just to put that in perspective, the human mouth also houses colonies of bacteria but a dog's mouth has been shown to house significantly more colonies than those of a human. For more information on both bacteria found on toilet seats and bacteria found in a dog's mouth, see the related links.
Bacteria is always present in the mouth.
Bacteria grows everywhere. There is even bacteria growing inside you, mainly in your mouth and your intestines. But your body, and most other living things, have ways of stopping the bacteria from overrunning them. Dead things do not, so bacteria can survive and reproduce as much as they want.