Which part of the standard syringe is responsible for penetrating the rubber stopper of the dental cartridge?

The harpoon is the part of the standard syringe that is specifically designed to penetrate the rubber stopper of the dental cartridge. This component plays a crucial role in the aspiration process, allowing the operator to check for the presence of blood in the cartridge, which indicates whether the needle is within a blood vessel. When the dentist or dental hygienist pulls back on the thumb ring, the harpoon engages with the rubber stopper. This mechanism ensures the integrity of the anesthetic delivery system and plays a key role in achieving successful local anesthesia while minimizing the risk of complications.

The other parts of the syringe, while important for the overall functionality and handling of the syringe, do not have the same direct role in puncturing the rubber stopper. The needle adapter secures the needle to the syringe; the finger grip provides stability and control during the procedure; and the thumb ring allows the operator to actuate the syringe. Each component is vital, but the harpoon specifically handles the critical task of accessing the anesthetic within the cartridge.