Scope of Practice, Supervision Levels, and Delegated Duties
Domain 3 tests the boundary lines: what a hygienist may do, under whose authority, and what must be referred to the dentist.
Supervision tiers
- Direct supervision: the dentist is physically present in the office, has examined the patient and authorized the procedure, and is available to intervene.
- General supervision: the dentist has authorized the service but need not be on the premises; the patient must still be under the dentist's care, with a documented examination and a way to reach the dentist in an emergency.
Which services fall under which tier is set by Board rule, not by office custom. If the rule does not place the task under general supervision, the dentist must be present.
Within scope under supervision
Prophylaxis and scaling, root planing, polishing, fluoride application, sealants, periodontal charting, exposure of radiographs, oral hygiene instruction, and screening observations reported to the dentist.
Outside scope, always
Diagnosis and treatment planning, prescribing, cutting hard or soft tissue, and independent practice. Expanded functions such as local anesthesia or nitrous oxide are state-specific and tightly regulated - verify current Board authority before performing any of them rather than assuming a neighboring state's rule applies.
Worked example
A new patient arrives in pain while the dentist is off-site. The hygienist wants to "just scale and polish." Analysis: a patient in pain needs examination and diagnosis first. Scaling without a documented dentist examination and authorization is out of scope, and treating pain as a hygiene appointment risks delay of care. The correct step is to arrange dentist evaluation or referral.
Traps
Mistaking "the dentist said it was fine last month" for a current authorization, and accepting delegation of a task that is not delegable - the hygienist shares liability for practicing beyond scope.