No provision of this chapter or of any other law shall prevent any person who holds a valid, unrevoked certificate to practice osteopathic medicine and surgery from using in combination with his or her name the designation "Osteopathic Physician and Surgeon" or the abbreviation of his or her professional degree, Doctor of Osteopathy (D.O.), provided he or she hold such professional degree, or any combination thereof upon his or her stationery, in any professional lists or directories or in other places where the same may properly appear as permitted within the canons of ethics approved by the board.