Retractable dental syringe

A retractable dental syringe, comprising:

• a tubular housing adapted to accept a carpule, the tubular housing having a front portion, an intermediate portion and a rear portion;
• a carpule having a fluid chamber, a front seal and a rear seal for enclosing fluid in the chamber, the carpule having a mouth in front and being sized to fit said housing;
• a depressible plunger which empties the carpule by moving the rear seal forward to an end-of-injection position;
• needle structure in fluid communication with the carpule, the needle structure being retractably mounted in the front of the housing for retraction into the carpule;
• whereby the mouth of the carpule is adapted to release the retractable needle for retraction into the carpule in response to depression of the plunger beyond the end-of-injection position of the plunger.

A method of operating a syringe, comprising:

• providing an elongated tubular housing having a front portion containing a retractable needle structure having a retractable needle holding part and a separable part which releases the needle holding part and needle for retraction;
• providing a carpule for the tubular housing, the carpule having a mouth in front with a front seal and a back portion with a slidable and separable two-part seal, the carpule having a fluid chamber between said seals in fluid communication with the needle;
• providing a depressible plunger having a tubular front portion in pressing contact with one part of the separable two-part seal;
• depressing the plunger to move the two-part seal forward to a sufficient extent as to expel substantially all fluid from the fluid chamber through the needle;
• and
• moving the carpule toward the needle structure in response to additional depression of the plunger to thereby automatically retract the needle holding part into the carpule through the mouth of the carpule.