What is not within the dental hygienist's scope of practice?

The correct answer highlights an important aspect of the dental hygienist's scope of practice. While dental hygienists are trained to provide various preventive and therapeutic services, the administration of local anesthesia typically falls outside their traditional responsibilities and requires additional certification or training beyond the standard education for hygienists.

Performing dental cleanings involves tasks like scaling and polishing teeth, which are core functions within the hygienist's role. Taking dental radiographs is also well within their scope, as assessing dental health often necessitates imaging. Additionally, applying fluoride treatments is recognized as a preventive measure that hygienists are authorized to perform.

Thus, while a dental hygienist plays a vital role in dental care, administering local anesthesia usually requires specific competency guidelines set by dental boards and may not be universally permitted in all practice settings without further qualifications.