California Code, Business and Professions Code - BPC § 1931

(a)(1) A dental hygienist in alternative practice may provide services to a patient without obtaining written verification that the patient has been examined by a dentist or physician and surgeon licensed to practice in this state.

(2) If the dental hygienist in alternative practice provides services to a patient 18 months or more after the first date that the person provides services to a patient, the person shall obtain written verification that the patient has been examined by a dentist or physician and surgeon licensed to practice in this state.  The verification shall include a prescription for dental hygiene services as described in subdivision (b).

(c)(1) The dental hygiene board may seek to obtain an injunction against any registered dental hygienist in alternative practice who provides services pursuant to this section, if the dental hygiene board has reasonable cause to believe that the services are being provided to a patient who has not received a prescription for those services from a dentist or physician and surgeon licensed to practice in this state.

(2) Providing services pursuant to this section without obtaining a prescription in accordance with subdivision (b) shall constitute unprofessional conduct on the part of the registered dental hygienist in alternative practice, and reason for the dental hygiene board to revoke or suspend the license of the registered dental hygienist in alternative practice pursuant to Section 1947.