Abstract: A dental handpiece head comprises a tool holder (17) driven by an eccentric crankpin (10) engaged in a vertical groove (18) of the tool holder. The axial displacement of the tool holder is limited by a finger (13) engaged in a transverse cutting (12) of the tool holder, the walls of which cutting define two axial limit stops. The relative position of these limit stops and of the groove (18) is such that when the tool holder is pushed back by the reaction to the penetration of the tool into the dental canal, the tool holder is driven only in alternating rotation, whereas it is driven in a combined rotational and translational movement when a traction force is exerted on the tool.This construction has the effect of suppressing the percussions of the tool in the tooth.

Abstract: The apparatus of the contra-angle type comprises an instrument holder sleeve driven in a combined movement of alternate rotation and translation by an eccentric stud fixed to the end of a flexible shaft consisting of a metal cable. It comprises a device for controlling the flexibility of the end of the cable, this device consisting of a ring mounted rotatably in a support which can slide in the body of the apparatus.