A cleaning powder device for use in a dental practice, comprising: - a main casing arm, elongated along a main longitudinal axis and comprising a distal end portion, configured as a nozzle for dispensing a mixture of air and abrasive powder, and a proximal end portion axially opposed to said distal end portion; - a secondary casing arm, elongated along a secondary longitudinal axis, incident with respect to said main axis and configured as a connector to a source of compressed air; - a pneumatic circuit formed in said primary and secondary arms between said connector and said nozzle; wherein - said main arm comprises, on said proximal end portion, releasable coupling means for a powder containment capsule, said releasable coupling means comprising a seat for inserting a neck of said capsule; - a free portion of a cannula, projecting along said main axis from said proximal end portion of said main arm, providing an insertion arrangement in an airtight fashion within said capsule; - said pneumatic circuit comprising, inside said cannula, two concentric channels with respect to said main axis, of which an external channel for the inlet of compressed air in said capsule, defined between an inner core and an outer shaft of said cannula, said external channel being in communication with a connector branch of said pneumatic circuit provided in said secondary arm starting from said connector, through at least one passage formed in said shaft, and an internal channel for drawing the air/powder mixture from the capsule, defined internally to said inner core, whereby said pneumatic circuit is configured inside said cannula to eject compressed air into the capsule, to create within it a turbulence allowing the mixing of air and powder, and to convey said mixture of air and powder towards said nozzle; wherein - said shaft has a shorter axial extension with respect to said core, leaving said core exposed for a free end segment, said segment comprising a plurality of orifices for communication between said capsule and said internal channel, said shaft comprising on its wall one or more air outlet holes of air from said external channel, formed in a region corresponding to said free portion of the cannula, and wherein - said releasable coupling means comprising locking means (21, 22) for said neck of said capsule, suitable for being released by manual intervention of an operator, said locking means (21, 22) comprising at least one locking member radially movable within said seat of said proximal end portion of said main arm, suitable for being engaged and disengaged with respect to said neck in order to axially retain the capsule in a locking or closing position, and to allow its insertion and extraction movement, in an open or release position. - a main casing arm, elongated along a main longitudinal axis and comprising a distal end portion, configured as a nozzle for dispensing a mixture of air and abrasive powder, and a proximal end portion axially opposed to said distal end portion; - a secondary casing arm, elongated along a secondary longitudinal axis, incident with respect to said main axis and configured as a connector to a source of compressed air; - a pneumatic circuit formed in said primary and secondary arms between said connector and said nozzle; - said main arm comprises, on said proximal end portion, releasable coupling means for a powder containment capsule, said releasable coupling means comprising a seat for inserting a neck of said capsule; - a free portion of a cannula, projecting along said main axis from said proximal end portion of said main arm, providing an insertion arrangement in an airtight fashion within said capsule; - said pneumatic circuit comprising, inside said cannula, two concentric channels with respect to said main axis, of which an external channel for the inlet of compressed air in said capsule, defined between an inner core and an outer shaft of said cannula, said external channel being in communication with a connector branch of said pneumatic circuit provided in said secondary arm starting from said connector, through at least one passage formed in said shaft, and an internal channel for drawing the air/powder mixture from the capsule, defined internally to said inner core, whereby said pneumatic circuit is configured inside said cannula to eject compressed air into the capsule, to create within it a turbulence allowing the mixing of air and powder, and to convey said mixture of air and powder towards said nozzle; wherein - said shaft has a shorter axial extension with respect to said core, leaving said core exposed for a free end segment, said segment comprising a plurality of orifices for communication between said capsule and said internal channel, said shaft comprising on its wall one or more air outlet holes of air from said external channel, formed in a region corresponding to said free portion of the cannula, and wherein - said releasable coupling means comprising locking means (21, 22) for said neck of said capsule, suitable for being released by manual intervention of an operator, said locking means (21, 22) comprising at least one locking member radially movable within said seat of said proximal end portion of said main arm, suitable for being engaged and disengaged with respect to said neck in order to axially retain the capsule in a locking or closing position, and to allow its insertion and extraction movement, in an open or release position.