Spray lacquer is the only thing I'll use on teeth, and even at that I try to avoid getting too much into the tooth surfaces. I spray from the center of the wheel out and try to avoid the tooth surfaces.
We did some testing on the Weird Gears Shark Bait. It is a hand operated kinetic sculpture. We tested without any finish, with finish sprayed from the center, and then with finish sprayed into the tooth surfaces. The last was a bad idea. Finish on the tooth surfaces greatly increased internal friction. It takes up space and also fluffs up the wood making for excessive internal friction.
It is best to avoid any finish on the tooth surfaces, but if you must, use spray lacquer lightly. It dries hard, but still, on humid days it is subject to moisture in the air that will make it tacky.