Systems and methods related to ultrasonic microtube dental instruments designed to cut around a broken instrument by allowing the broken instrument to be placed within a lumen of the microtube instrument while simultaneously boring with the broken instrument and being guided by the broken instrument...http://www.google.com.hk/patents/US6976844?utm_source=gb-gplus-share專利 US6976844 - Ultrasonic microtube dental instruments and methods of using same
