Abstract: In general, the invention consists of an indicator means for indicating the usage of an endodontic instrument by providing a visual indication of the number of sterilizations of the instrument. The indicator includes a modified “stop” or “washer” which is used with each endodontic instrument. The “stop” includes a dye compatible base which is impregnated with a diffusible dye composition. The base is made of a dye compatible material which enables the diffusible dye to migrate or diffuse as a result of a specific number of sterilizations at a specific temperature from an interior portion in the base where the dye is not visible to an exterior position where the dye is visible. Since the “stop” is also sterilized along with the instrument, the “stop” will change color after a specified number of sterilizations of the instrument has occurred.