A special license shall be required for the practice of each special area of dentistry recognized by the American Dental Association, in order for a dentist to hold himself out to the public as limiting his practice to, being a specialist in, or giving special attention to any special area of dentistry. No dentist shall announce or hold himself out to the public as limiting his practice to, or as being a specialist in or giving special attention to, any special area of dentistry without first having obtained a special license therefor from the board as herein provided. The volume of business performed in any limited area of dentistry and the restriction of a licensed dentist’s activity to any one or more limited areas of dentistry shall not in themselves constitute a holding out to the public that the dentist is a specialist.