The appliance includes a jet source of fluid, and a nozzle assembly (10) through which the fluid is directed and then out for application to the teeth. A flow interrupter assembly is mounted within the nozzle assembly, such that the interrupter assembly (20) is responsive to the fluid flow to produce momentary successive interruptions of the fluid flow by the action of the interrupter assembly moving from an original position to a flow interrupting position and then returning to its original position as the flow decreases and then is interrupted, due to the fluid flow itself, resulting in a cyclical perturbation in the fluid flow from the nozzle, by flow action alone.
