S.C. Code Ann. § 40-15-330

Upon completion of the dental technological work, the appliance shall be returned to the dentist by whom ordered or his office, the name or number of the written work authorization accompanying the invoice. Each work authorization or copy thereof shall be retained and filed by the person doing the dental technological work for a period of at least three years. The work authorization or copy thereof shall be available for inspection by the board, or its duly authorized agents, on the premises during such period.