Abstract: The invention relates to a medical or dental-medical apparatus (1), having a delivery line (31) for a liquid and having a screw bushing (17) onto which a container (14) for the liquid can be screwed, the delivery line (31) extending from the interior of the container (14) to the outside and penetrating the screw bushing (17), a compressed gas line (39) penetrating the screw bushing (17) from the outside inwardly, and the compressed gas line (39) being closable and openable by means of a valve (41). In order to simplify the operating effort, the screw bushing (17) is rotatably mounted in a rotary bearing (26) and stands in working connection with a switch cam (44) which, in a rotary position of the screw bushing (17) which is rotated in the screwing-on direction (45), opens the previously closed valve (41).