Abstract: An injection device for a dental anesthetic or the like is constituted such that the linkage between the rear end side of an operating rod provided so as to freely go in and out of a main body and a drive mechanism operated by a motor provided in the main body is made detachably and the connecting or disconnecting operation of the drive mechanism and the rear end side of the operating rod is carried out by means of a manipulation portion provided in the main body.

Abstract: A dental detection apparatus for the position of a root apex comprises two oscillators for generating the currents having two different frequencies passing between a single electrode contacting to a patient's body and a reamer, a differential amplifier for detecting the difference .DELTA.

Abstract: A block-like tool has a hole in its upper surface and contains a hollow needle projecting at one of its ends into said hole and opening at its other end to the atmosphere. Said hole is disposed removably to receive and stably support therein the lower end of an empty, tubular ampule, which is hermetically sealed at its lower end by an elastic diaphragm. Said needle pierces said diaphragm when the ampule is mounted on the tool, whereby the interior of the ampule is also brought to atmospheric pressure through said needle thus enabling the withdrawal of an elastic plug from the ampule, and the refilling of the ampule with a solid alginate without encountering pneumatic resistance.