Wash. Rev. Code § 18.29.050
Any person licensed as a dental hygienist in this state may remove deposits and stains from the surfaces of the teeth, may apply topical preventive or prophylactic agents, may polish and smooth restorations, may perform root planing and soft-tissue curettage, and may perform other dental operations and services delegated to them by a licensed dentist or dental therapist. Any person licensed as a dental hygienist in this state may apply topical anesthetic agents under the general supervision, as defined in RCW 18.260.010, of a dentist or a dental therapist: PROVIDED HOWEVER, That licensed dental hygienists shall in no event perform the following dental operations or services:
(4) The taking of any impression of the teeth or jaw, or the relationships of the teeth or jaws, for the purpose of fabricating any intra-oral restoration, appliance, or prosthesis, except that a dental hygienist may take an impression for any purpose that is either allowed:
[ 2023 c 460 s 20; 2015 c 120 s 1; 2013 c 87 s 1; 2003 c 257 s 1; 1997 c 37 s 1; 1971 ex.s. c 235 s 1; 1969 c 47 s 4; 1923 c 16 s 27; RRS s 10030-27.]
Effective date—2023 c 460 ss 1-22: See note following RCW 18.265.005.