Any person licensed to practice dentistry or dental hygiene in this state who has retired or may hereafter retire from such practice in this state is not required to register as required by this chapter; provided, that such person files with the board an affidavit on a form to be furnished by the board, which affidavit states the date on which such person retired from such practice and other such facts as tend to verify such retirement as the board deems necessary. If such person thereafter reengages in the practice of dentistry or dental hygiene in this state, such person shall apply for registration with the board as provided by this chapter.