California Code, Business and Professions Code - BPC § 1912

Any procedure performed or service provided by a registered dental hygienist that does not specifically require direct supervision shall require general supervision, so long as it does not give rise to a situation in the dentist's office requiring immediate services for alleviation of severe pain, or immediate diagnosis and treatment of unforeseeable dental conditions that, if not immediately diagnosed and treated, would lead to serious disability or death.