Abstract: A power driven mechanical toothbrush is disclosed. A replaceable toothbrush head member has tuft blocks retained generally therewithin and extending laterally outwardly from the a cam shaft. Each tuft block has at least one tuft of bristles, usually four, secured within the tuft block and extending upwardly therefrom. Each of the bristles has a distal end at a distance from its tuft block, and the bristles in each tuft are generally parallel to each other. The toothbrush head member is adapted to receive and retain the tuft blocks in sliding relation therein, so that each tuft block slides linearly in a direction parallel to the longitudinal tuft axis as guided by guide rails within the head member, between a retracted position and an extended position. Each tuft block is driven from its retracted position to its extended position by the rotatable cam shaft.