1. Does good dental care (mine) lessen the risk?

If you use an antibacterial mouthwash (Listerine), it might, but if you don't have E. coli in your system you won't digest your food well, which should cause you some discomfort, at least.

2. If I'm using the tip of my tongue to pass mostly water, am I increasing or decreasing the risk?

3. On a scale of 1-10 (10 being high risk), where does this fall?

Geez, I'm not a statistician! Lulu periodically gets after my mouth, has for years, and has never gotten sick, but I've also seen birds die from E. coli infections. I think it's almost impossible to totally avoid this risk, but I also think it's prudent to be aware of it and minimize it. I don't allow my birds unrestricted or frequent access to my mouth, or food that's been in it, (unlike people I know who let their parrots pick their teeth and think it's cool), but I don't get paranoid about keeping them away from my mouth, either.

Sometimes I think moderation is the answer to almost everything, and I HATE it! Our birds (and us) are constantly exposed to a veritable barrage of deadly bacteria in our tap water, air, food, etc. When we used to prep animals for surgery, we rinsed them off with tap water and I asked Doc once, "Aren't there bacteria in this water?" He replied, "Yes, there are. But the risk is minimal because it's a numbers game. It takes hundreds of bacteria to start an infection, not 1 or 10."

At a practical level, I get careful about it with stressed, molting, or sick birds and don't worry too much about it with healthy ones.

Side note, since I mentioned tap water, is that the additives and heavy minerals in tap water are not particularly good for your birds. I use a filter pitcher for bird water and boil any water that will be used for mixing baby formula. Also, if you travel with your bird or ship a bird, give bottled water while traveling, and for a few days gradually mix the "new" water with the bottled water to get the bird switched over. This avoids the birdie equivalent of the "Mexican Potty Trot" dance.

One more helpful tip: In the ongoing war against microscopic bugs, your microwave is one of your best allies. Four minutes in the microwave on high will kill ANYTHING - bacteria, viruses, fungi, etc. It's a quick, easy way to "sterilize" toys, blankies, water, twigs, food dishes, etc., without worrying about disinfectant residue. (It's best to put a small bowl of water in with dry objects so the oven doesn't explode. :-D )