The last two people I fought for to get implants covered in Medicare were turned down. As most here know, I came out of the dental implant industry and designed and sold them worldwide through my company. They have never been covered even by dental insurance and were always private pay, (my wife is still a rep for Astratech, part of the giant pharma company Astra Zeneca, one of the world's largest implant manufacturer's and the reason I am able to donate my time to OCF instead of work at McDonald's for a living.)
The only people I have seen get Medicare covered implants are completely edentulous on the arch in question, and those are always mandibular arch reconstructions done with a pair of implants and a bar between them that a denture then snaps to. This is a nice restoration and very effective, though most people who are partially edentulous think of porcelain crowns on top of individual implants, which I have not seen covered no matter the cause for the tooth loss. Medicare in interested in restoring function only, which the two implants and over denture design does quite well, and will spend no money for things more.