The following practices, acts, and operations are excepted from the operation of this chapter:
(1) The practice of dental hygiene in the discharge of official duties by dental hygienists in the United States armed services, coast guard, public health services, veterans' bureau, or bureau of Indian affairs;
(2) Dental hygiene programs approved by the secretary and the practice of dental hygiene by students in dental hygiene programs approved by the secretary, when acting under the direction and supervision of persons licensed under chapter
18.29 or
18.32 RCW acting as instructors;
(3) The practice of dental hygiene by students in accredited dental hygiene educational programs when acting under the direction and supervision of instructors licensed under chapter
18.29 or
18.32 RCW; and
(4) The performance of dental health aide therapist services to the extent authorized under chapter
70.350 RCW.