Abstract: A fountain toothbrush has in its handle a toothpaste reservoir constantly pressurized by a charge of actuator gas acting through a cup-like piston disposed at the upstream end of the reservoir. The gas pressure pushes the piston and toothpaste downstream while resiliently urging the piston sidewall against the reservoir boundary wall to forwardly extrude toothpaste adjacent the boundary wall. A valve for selectively passing toothpaste from the reservoir to the brush head includes an apertured gate and a structurally separate actuator for translating the gate in a valve chamber in opposition to a bias spring. Separating the gate from the actuator permits the gate to be positively sealed against the chamber outlet by the toothpaste in the closed valve position. A lengthwise segment of the gate has a reduced thickness dimension so as not to fill the upstream side of the valve chamber, thereby avoiding the creation of a partial vacuum that would otherwise hold the gate in its open position.