Just to let you know that keeping root canaled teeth is having dead tissue in some energy meridians so be aware of the connections between the specific teeth and certain organs, and watch out for symptoms. Ozone therapy can temporarily provide inhospitable environment to bacteria but with time, as the materials degrade bacteria will find their way in (again its a dead tooth). Ozone therapy ideally should be done every few months to keep bacteria away (I dont have experience with this therapy by the way). I'm not sure how ozone therapy will be done after a crown is placed. You can get non metallic crowns; there should be all ceramic, and all porcelain, as well as resin type; all these are not as resistant as porcelain to metal crowns, but its definetely a better choice than having metals in your mouth (specially if you have different metals as this creates a battery effect which will leach the metals away faster and creates disturbances with its electrical output).
Mike