secured on the rotor conical end tip forming with the housing vertax wall 12 a one ball thrust bearing the stepped rotor has a front portion of a larger circumference than its rear portion the radially extending dimensions of the rotor vane 39 s front portions 6a being greater than the corresponding radially extending dimensions of the rotor vane 39 s rear portions 6b the rotor has pins 21 equally spaced on its front main body portion 6c to extend forwardly thereof the shaft 7 flexibly connected with the rotor is secured in the rear bearing 24 and the front bearing 25 of the front cover 5 there are radial slots 26 equally spaced on a shaft flange 23 that forms a rear portion of the shaft the pins 21 engaged with slots 26 form a coupling between the rotor and shaft that permits limited axial and radial floating movement of the rotor relative to the shaft and working chamber an opposite shaft end has a shaped blind hole 27 for the brush installation to perform different tasks in everyday tooth and gum care sets of different types of exchangeable and disposable brushes can be used with the same hydraulic.