In combination these help change the pH of the dog's mouth to make it a more hostile place for bacteria and to discourage tartar formation. (dogplaqueremovaltips.com)
This changes the properties of his saliva, to make the mouth a more hostile place for plaque to develop. (dogplaqueremovaltips.com)
But outer space is an extremely hostile place and could kill you if you aren't protected. (science.howstuffworks.com)