Abstract: The invention relates to a turbine handpiece (1), in particular for medical or dental-medical purposes, having a drive shaft (2), rotatably mounted in the forward end region of the handpiece (1), with which a tool can be connected by a mounting device, whereby there is arranged on the drive shaft (2), fixed for rotation therewith, a turbine wheel (4) in a turbine chamber (5), in which a delivery line (11) for a flowing pressure medium opens at an inlet opening (11a) and from which a discharge line (12) extends at an outlet opening (12a), whereby a apparatus (22) is provided which after a switching-off of the pressure medium supply, during the running on of the turbine wheel (4), prevents a release of the pressure medium rotating in the turbine chamber (5) through the discharge line.

Abstract: In a medical, in particular dental turbine handpiece, having a supply line (8) and a discharge line (9) for the turbine compressed air, whereby a valve (12) is arranged in one line, which valve is controllable by a pneumatic parameter in the other line, the valve (12) is arranged in the discharge line (9) and is so controllable that it closes when a limit value of the parameter in the supply line (8) falls below a minimum value.

Abstract: In a medical or dental treatment instrument, in particular a straight or angled handpiece (1), having a drive shaft (6) for a tool, which drive shaft is mounted in the forward end region of the treatment instrument, in at least one roller bearing (11, 12), rotatable around its middle axis (8), and is drivable for example by a turbine, whereby the roller bearing (11, 12) is blocked or sealed against contaminants with of a blocking ring (31) effective between its outer ring (37) and its inner ring (34). The blocking ring (31) bears with its surface facing the inner ring (34) on the inner ring (34) and is releasibly or non-releasibly attached thereon.