Trephine Drills With Central PinDSI Trephine drills with a central pin are made for conducting a precise socket for a bone ring. The drills have an integrated central pin that stabilizes the drill during the procedure and delivers filigree accuracy for the socket. To begin the drilling sequence with this trephine drill, first, you need to perform an initial socket preparation with a lance drill to center the pin in it. DSI Trephine drills are built from high quality stainless steel.