A compressed air handpiece comprising a handle (32) which connects to a head (34) within which a turbine (36) is housed, the turbine (36) comprising a movable wheel (38) from a periphery (40) from which extend a plurality of vanes (42) which define an outer diameter (44) of the movable wheel (38), the handpiece (30) also comprising injection means having the function of directing on the vanes (42) of the moving wheel (38) a flow of compressed air whose pneumatic energy is converted into kinetic energy when the flow of compressed air strikes the vanes (42) of the moving wheel (38) the handpiece (30) further comprising an exhaust duct (58) in the handle (32) of the handpiece (30) and through which the air escapes after striking the blades (42)； ) of the impeller (38), the handpiece (30) being characterized in that the exhaust duct (58) communicates with the head (38) via an o the opening which is at least opposite the zone in which the compressed air strikes the blades (42) of the impeller (38), and in that the means for injecting the compressed air extend to the interior of the exhaust duct (58), this opening completely surrounding the means for injecting the compressed air, the means for injecting the compressed air being in the form of an insert (46) at inside which is provided a conduit (48) for supplying the flow of compressed air and which is attached to the interior of the handle (32) of the handpiece (30).Pièce à main à air comprimé comprenant un manche (32) qui se raccorde à une tête (34) à l'intérieur de laquelle est logée une turbine (36), la turbine (36) comprenant une roue mobile (38) depuis une périphérie (40) de laquelle s'étendent une pluralité d'aubes (42) qui définissent un diamètre extérieur (44) de la roue mobile (38), la pièce à main (30) comprenant également des moyens d'injection ayant pour fonction de diriger sur les aubes (42) de la roue mobile (38) un flux d'air comprimé dont l'énergie pneumatique se transforme en énergie cinétique lorsque le
