Endodontic ozone apparatus for the treatment of root canals includes the source of ozone, an aqueous medium, and a system for ozonating the aqueous medium. A syringe includes a needle insertable into the root canal and a plunger may be utilized for charging the syringe with ozonated aqueous medium. An ozone sensor, which may be an ink, is utilized for determining the ozone content in the aqueous medium before introduction of same into the root canal of a patient.