Abstract: A chuck for receiving a plain shank of a dental burr is rotatably mounted in the head of a dental handpiece and is driven by a pinion or by turbine vanes. The chuck comprises a sleeve adapted to receive the shank of a burr and provided with at least one elongate clamping claw which is movable radially between an inner clamping position and an outer releasing position. Facing grooves in the clamping claw and in an actuating member which is movable axially relative to the sleeve define a ramp way for a row of bearing balls. The ramp way extends in a direction which is generally axial but is inclined at an angle of 1.degree. to 4.degree. to the axis so that the clamping claw is moved radially by axial movement of the actuating member. The clamping claw is spring biased to clamping position and is movable to releasing position by a push button for moving the actuating member axially relative to the sleeve and thereby moving the clamping claw radially outwardly.

Abstract: The contra-angle is provided with means for illuminating the site of treatment. The light source is incorporated inside the body of the contra-angle, and in front of this light source is inserted an optical element arranged to deflect the light rays towards the site of treatment. This optical element comprises a total reflection prism embedded in a recess in the body of the contra-angle.