System for protection of soft tissues against a teeth whitening substance

The appliance includes a brushhead having conductive fiber bristles by which a potential is applied to electrochemically activate a teeth whitening substance, such as peroxide, in the vicinity of the teeth. An impedance appliance system (62) or an optical appliance system (27) provides information concerning whether the conductive fiber bristles are adjacent a tooth surface or gum region. The impedance system uses an electrical signal through the fiber to determine the impedance of a circuit which includes the tooth or gum surface, the impedance being different, depending on whether a tooth or gum surface is in the circuit. The optical system generates a light beam which is directed to the mouth surface through a conductive fiber, the color of the returning light indicating whether the surface is a tooth or gum region. If a tooth is determined, the teeth whitening substance is activated at that bristle, while if gum tissue is determined, the teeth whitening substance is not activated at that bristle.