I'm not familiar with Mercedes differentials specifically, they're not limited slip differentials are they?
Are you talking about the small bevel pinions or larger bevel gears inside the differential (the bevel gears are fixed to the axle shafts, and the bevel pinions are mounted to the differential carrier gear and mate to the two bevel gears)? Because the small bevel pinions rotate whenever there is relative movement between the two rear wheels. So, like, every time you turn.
Also, the bevel pinions transmit the full driving load from the carrier gear (which is driven by the drive shaft) to the bevel gears (fixed to the axles). So if that tooth with the missing chuck happens to be engaged when you're driving, you'll have much higher stresses in the remaining tooth, so it could be a problem.
All of this could be WAY off if I misunderstood your initial question. I'm just going off of how differentials work in general. And, for goodness sake, find the chuck of tooth and put it on your shelf
