An oral hygiene appliance is of the kind which includes a supply of liquid, a pump and a hand-held tip for directing the liquid where desired. A housing defines a cavity which has a surrounding wall closed by opposing end walls, the pump being seated within the cavity. A reservoir is closed at one end and has a shape in conformity with the housing to telescope thereover in covering relationship. Defined in one end of the reservoir is a valve seat which cooperates with a valve that closes during removal of the reservoir from the housing. On that end of the reservoir also is a coupling element which cooperates with a coupling member disposed in the surrounding wall of the housing. When that coupling relationship is established, the reservoir is seated on top of a side surface of the housing which, in turn, is lying on a table or the like. An outlet in the housing communicates with the hand-held tip and the pump is connected between that outlet and the coupling member. Particular pump structure, electrical switching mechanism and other mounting and assembly features are described and illustrated.