First, a bit of history. This isn't an assembly line. Therefore, we need to split the process into basic principles and flexible options. Minimal head tilt. Which brings us to a flexible view of posture and positioning .
Spines get nourishment through motion.
If you convert to a fixed focal length, for example with a microscope, you do so at great personal risk, especially if you perform long detailed procedures such as endo or crown and bridge. Allows the operator to sit, stand or sit-stand in function. Allows the assistant to sit, stand or sit-stand in function. I'm already working more hours than I'd like to admit. Our studies have shown that, even in successful practices, significant time and energy are spent every day on unproductive effort.