I recall once it being linked to tooth decay and then of course the old movies promoting abstinence that we were shown in high school alluded to a direct association to diabetes, cancer, arthritis and chronic flatulence.
 Bottom line!: You're probably more likely to contract a STD from little Suzy Rottencrotch working the checkout stand at the market than one of our communities safety conscious professionals. The ladies here don't like being looked at as petri dishes to be handled only while wearing surgical gloves, and if you think about it neither would you.

   AINQ.

Two suggestions, used seperately or together...
1.  Put a condom on your tongue.
2.  Place a plastic bag over your head.

Almost didn't bother replying to this... but I just couldn't resist.  Are you really serious... making DFK safer?  What do you want to do... coat your mouth with latex???????  Fluid transfer is how MOST infectious disease are caught.  The worst you can catch is an STD?  Are you kidding?  Ever heard of hepatitis?  Good grief.

That being said, I can honestly say that I've never caught anything by kissing.  I love DFK and can't imagine giving it up.  To me, the risk simply isn't big enough for me to be concerned over, statistically speaking.  

But, at the risk of sounding redundant, would you PLEASE get accurate information?  Then, calculate your risk, and take only those risks that you are willing to take.  

Okay, off my soap-box now.......