Abstract: A device for treating teeth with a tooth treating medium, such as a fluorine-containing agent, in which two U-shaped trough members are formed of a soft synthetic plastic. One of the trough members is designed to be applied about the upper teeth and the other about the lower teeth. The upper and lower trough members are interconnected at their bottom by a single centrally located connector element. A forwardly projecting handle on the connector element enables the device to be hygenically handled. The two U-shaped members are centered relative to each other by two sets of intermeshing ridges thereon.