Offer valid through 12/31/10. Buy 3 Prophy Gems (100/box), get 1 free! To receive your free good, please send a copy of your Patterson invoice to: Biotrol, PO Box 7926, Algonquin, IL 60102 or fax to 847-458-0063. Qualifying purchase(s) must be on one invoice. Requests must be received no later than 1/15/11. For questions about free goods, email [email protected].