Abstract: A digital compensation circuit for improving the temperature stability of dielectric resonator oscillators is disclosed. A temperature sensor indicates a measure of ambient temperature which is correlated with an amount of phase shift necessary to compensate for frequency drift in a dielectric resonator oscillator. The correlation is made using a correction table or correction function which is determined empirically in a calibration process. The necessary phase shift is then supplied via a voltage controlled phase shifter. This phase shifter is part of the RF oscillation loop which also includes an amplifier, directional coupler and dielectric resonator filter (including microstrip).

Abstract: A syringe for extruding heated thermoplastic materials through a hollow needle is disclosed. This syringe is particularly useful in obturating root canal cavities, or other dental cavities, with gutta-percha or similar materials.

Abstract: An electrically heated endodontic syringe for injecting thermoplastic material, such as gutta percha, into a root canal cavity includes a syringe barrel for holding a supply of thermoplastic material, a heater body threadedly attached at one end to the syringe barrel and an injection needle threadedly secured to the other end of the heater body by means of a hub. A manual plunger is provided in the syringe barrel for ejecting thermoplastic material from the barrel through the heater body, hub and needle into the root canal cavity. The barrel and plunger are made of materials having a low coefficient thermal conductivity of less than about 20 Btu/(hr)(ft.sup.2) (F..degree./ft) and a thermally insulating washer is positioned between the barrel and the heater body to minimize heat transfer to the barrel. The heater body, hub and needle are made of materials having a high coefficient of thermal conductivity of at least about 200 Btu/(hr) (ft.sup.2) (.degree.F./ft) to maximize heat flow to the needle.