And the opposite for others. For example, getting cavities filled in the front of the mouth probably benefits from laying face up so that any saliva that's generated flows back down the throat instead of to the front of the mouth.

I'm guessing a lot of existing techniques and tools have an implicit bias for the patient being face up.

> I'm guessing a lot of existing techniques and tools have an implicit bias for the patient being face up.

Well, they have a bias for a human doing the dentistry. With all that entails.