I am at age 61 and had tooth 14 and 15 implants done in 2015, but failed in 2024, due to tooth 15 bone lost. Both teeth crowns are joint with sinus lift. The doctor who did my implants originally tried to save tooth 15 implant by doing bone graft but could not fully recover tooth 15 bone. He said it has risk to restore crown on tooth 15 implant as it may loss bone again. Should I leave tooth 15 implant without crown? Tooth 18 also has crown.