Mich. Comp. Laws § 333.16641: Work authorization for dental laboratory services required; retention and inspection of work authorizations and copies.

Sec. 16641.

A dentist shall not use the services of a dental laboratory without furnishing a written work authorization to the dental laboratory and a carbon copy to the patient for constructing, repairing, or altering prosthetic dentures, bridges, orthodontic or other appliances, or structures to be used as substitutes for or as a part of human teeth or jaws or associated structures, or for the correction of malocclusions or deformities.

A dentist shall retain a written work authorization furnished to a dental laboratory or a copy of the authorization for not less than 3 years and allow the board, its agents, or employees to inspect the file of written work authorizations or copies.