For thousands of years humans lived together intimately without bottled mouthwash, toothpaste, underarm deodorant or dipilatory creams.
Then, some smart merchandizer started advertising an incessant message: YOUR BREATH STINKS, YOUR TEETH AREN'T WHITE, YOU'RE PITS ARE ODIOUS, and HEY LADY, YOU'VE GOT A MOUSTACHE ON YOUR LIP!
I don't think we need advertisers to tell us that stinky breath is stinky.
Actually the practice of brushing your teeth is pretty old. Ziddina already mentioned the Egyptians.
According to the second most holy book to muslims after the Quaran, the Sahih Bukhari, Muhamad would brush his teeth every morning with a Siwak.
"Allah's Apostle said, 'If I had not found it hard for my followers or the people, I would have ordered them to clean their teeth with Siwak for every prayer.' (Translation of Sahih Bukhari, Friday Prayer, Volume 2, Book 13, Number 12)
"Allah's Apostle I said, 'I have told you repeatedly to (use) the Siwak. (The Prophet put emphasis on the use of the Siwak.) (Translation of Sahih Bukhari, Friday Prayer, Volume 2, Book 13, Number 13)"
And that, by the way, is much better advice than you'll find anywhere in the Bible.