A reusable dental syringe including a conventional medication filled carpule and a conventional double ended needle cannula which is to be retracted into a compact enclosure to permit the safe handling and disposal of the cannula while avoiding an accidental needle stick and the possible spread of disease....http://www.google.com.au/patents/US4919657?utm_source=gb-gplus-sharePatent US4919657 - Dental syringe having a medication filled carpule and a retractable needle cannula
