A control method is provided for controlling a heating of a thermal optical element, the thermal optical element having a matrix of heater elements. A preset number of objects are counted and stored in dedicated chambers, the combination of the numbers of objects within the chambers being known to comprise any number of objects which is desired for dispensing. A flow connection, starting from the area of the intermediate space between the seals, extends to the interior space and is provided with a nonreturn valve, through which a flow can proceed only in the direction of the interior space. This engagement between the protuberance and the recess locks the cartridge onto the manicuring machine during normal use without the need for a separately actuated locking pin. The bottom electrode must be specifically fabricated using a refractory metal to allow the formation of the solid-state electro-optic material.