| 摘要 |
A reusable dental syringe having a hollow cylinder, a prefilled medication carpule to be received within the cylinder, and a hypodermic needle cannula communicating with the carpule and extending outwardly from the cylinder for administering an injection. The syringe also includes a retaining collar which can be moved, against the normal bias of a compression spring, axially and distally through the cylinder and into engagement with the carpule. A slide lock is adapted to lock the retaining collar at the distal position within the cylinder. After a injection has been administered and the carpule emptied, the slide lock may be moved to release the retaining collar from the distal position. The compression spring is now free to return to its normal bias, whereby to drive the retaining collar and the empty carpule connected thereto axially and proximally through the cylinder. Accordingly, the needle cannula is automatically relocated from the outwardly extended position to a retracted position within the cylinder so as to prevent an accidental needle stick and the spread of a contageous, and possibly life threatening, disease.
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