Well, we gave you advice, I do hope you take it. If not, hopefully someone else having this problem will find this thread and will take our advice.
If you really are gonna fret about any time another dog puts his mouth on yours, then be prepared to either keep your dog away from other dogs, or get him a plastic bubble because sorry, but they are DOGS and thats how they play and communicate.
Maybe you could pass by a local dog park (Without your dog) just to observe. you can learn a lot about dog body language just by looking and checking them out playing with eachother. so next time you know what is prefight behavior and what is play