Functional handpiece 1 having an elongate handpiece body which has at its rearward end a connection element for connection with a flexible supply line, and has at its forward end a light emission element of a light permeable material for the illumination of the treatment site, and has in the light emission element an outlet opening for a medium such as water or air or spray, the light emission element forming a forward region of the functional handpiece and being releasably connected with the remaining region of the functional handpiece, and the light emission element having a plug-in fitting for the light emission element. In order to improve the functional handpiece with the regard to the illumination of the treatment site, the light emission element is connected with the remaining region of the functional handpiece by means of a latching device, the latching device having a latching nose directly or indirectly arranged on the light emission element, which can spring in radially inwardly and can self-actingly spring out behind a latching edge on the plug-in fitting.