A mixing chamber for a handpiece of a medical device, in particular a dental abrasive jet device, having a first supply line for a first fluid stream, in particular a liquid fluid flow, and a second supply line for a second fluid flow, in particular a powder/air mixture, where the two supply lines extend along a central axis and the second supply line-ends within the mixing chamber in an outlet the mixing chamber having a mixing region, in which the first fluid flow is deflected towards the second fluid flow, downstream of the outlet, and an accelerating region in which the first supply line extends parallel to the second supply line over the length of at least 3 mm.