Can I restore this with a screw retained custom abutment?

The internal screw threads already seem damaged... I'm afraid you can't.

No, you cannot, but it’s not clear from the description if the prosthesis failed clinically or your decision is based on the X-rays “symptom” only?

Do you have a panorex to post? I'm curious about the occlusion, it seems that this was a retreat of the medial implant,breakage of the abutment screw? There seems to be no threads in that implant abutment and it is failing again.Also the second molar appears to be failing with the premolars soon to follow. Bruxism? Traumatic occlusion? To just try and treat the loose implant crown may miss etiology of the failure.

Something is fishy about that anterior abutment. It's possible someone already damaged the threads and possbily attempted to cement a custom post into the implant body. You can attempt to section the anterior crown free and try to rotate it out or cut it down to expose the screw (if there is one). I would inform the patient that there is a good chance the top portion of the implant is damaged or will be damaged trying to loosen the crown. If you can't get the screw or post free, you'll have to drill it out. Your options after that are to: 1) drill into the implant and create a longer post-space for a custom post, or 2) trephine the anterior implant, graft, and replace (you may attempt to replace immediately with a wider diameter implant if the ridge is wide enough.

Too late, if you look closely the threads are gone already. Go back to square one, remove the implant with a trephine and replace with a new fixture the same day.

whatimplantisthis.com to identify implants If it is a press-fit style implant/abutment connection, you may be salvageable, existing abutment obviously doesn't fit closely. Evaluate your options after you access the connection. If #19 is loose, it's splinted mate, #18 will fail. Almost looks like they customized the implant/abutment connection instead of the abutment/restoration connection. Please update us when you learn more.

Run away from this case dude! This nightmare now becomes yours if you accept "trying" and inevitably failing with this. If the prosthesis loose? Why are you even thinking about replacing this restoration?

CRS and Dr. G are right. . . need a better PA for starters and reimplantation is a must. Based on what you've got, looks as though the abutment on the posterior implant was not tightened flush to the fixture (cantilevering). Looks like Zimmer or 3M implants based on my experience. . . please review implant specs before placing! Implants with straight-body design allow too much stress from occlussal force on the top of the implant as well as the cortical bone surface (this can present micro-movement of the screw and cause cantilevering). Trephine, augment and start over. Please update!