Power
As a dental assistant, you're not exactly considered a power broker. First, you don't have much control over your schedule. You work when the dentist determines that s/he needs you, and the dentist's appointments also determine your job tasks.
If you're assisting at a filling procedure, for example, you lay out exactly the equipment and supplies the dentist needs. If you're prepping for a tooth extraction, you probably add some extra damage control equipment. If the dentist is running behind schedule, you must stay until the last patient has departed. Too bad you'll be late to your son's baseball game. You don't have much choice in the matter.
However, you do wield a peculiar kind of power, without which the dentist would fall flat on his face: You can set the stage for the dentist's success. You prepare each appointment's equipment and supplies, update the patient's information, and help him calm down before the dentist arrives. When the dentist has completed his work, you efficiently deliver follow-up instructions to the patient.
In short, you're the vital link between the dentist and the patient. And there's definitely a sense of power in that.