Can a hygenist work without a doctor in the office?

In the United States, the answer depends on the specific state laws that govern the practice of dentistry and dental hygiene.

Some states allow hygienists to practice on patients of record without the dentist being in the office. Other states prohibit this. At least one state, Colorado, allows dental hygienists to practice completely independent of dentists. You should consult the Dental Practice Act of your specific state for the correct answer.