No. Just cut them when they are long.
It's actually nasty at the thought of it. I'm not saying MY nails have scum and dirt, but biting them would just put that into your mouth..
I can think of a few things that are very common and way nastier if the definition of nasty is dirt and bacteria:
- Showering without frequently cleaning out the shower head
- Eating a girl out (unless she just showered, WITH a clean shower head

)
- Leaving food on the counter and eating it the next day
- Licking your finger when turning a paper
- Coughing / other people coughing near you
It's obviously only since I bite my nails that I felt the need to go in defensive stance, but the nail thing really strikes me as retarded. Then again, my nails are generally always short due to biting, so there's nowhere for the "dirt" to get stuck, and maybe you can't relate due to being used to having long nails
I do hate that I do it though, cause it looks bad, both your fingers and you while you're doing it. It's a subconscious compulsion that I don't really always control. I bet the hair under my arms is nastier after a workout session than my fingernails can ever be. And obviously I'd love to lick the hair under my arms after a workout session without even flinching.