Abstract: An endodontic syringe for injecting thermoplastic material, such as gutta percha into a root canal cavity. The syringe includes a drive motor and mechanism for reversible axial translation of a plunger, a removable gutta percha cartridge and needle, and a heating element surrounding the cartridge to heat the gutta percha to a fluid condition. Forward movement of the plunger, against a piston within the cartridge, ejects gutta percha for the cartridge and needle. Reverse movement of the plunger returns it to its starting position, at which the used cartridge can be removed and replaced.The cartridge and needle are of aluminum or aluminum alloy.

Abstract: A controllable frequency ultrasonic signal generator for driving an ultrasonic transducer via a switching type output circuit for the efficient transfer of energy thereto. The signal generator includes a phase lock loop feedback control for locking the operation of the oscillator to the resonant frequency of the transducer for following variations in transducer resonant frequency due to loading changes, temperature changes, tool tip variations, and the like.