With as much bone loss to the apical I would try to counter rotate the fixture which may break what little integration remains. If this doesnt work then you can use a peizo to carefully circumferentially remove bone to implant connection or in the absence of a peizo a trephine on a implant drill with alot of irrigation is needed to cut to the level of the implants apex. I would then currette the site aggressively, flush with saline with doxy in it, then pack the site with a graft laced with doxy get primary closure place on systemic antibiotics and let it heal for 2-3 months before attempting a new implant.

I usually use a round bur intially and then switch to my mectron unit. Piezosurgery is the way to go especially in the mandible to avoid nerve damage. However I have broke some tips when I touched the implant.

Only way I know is via a trephine. I think its the best and only way.