Implant failed: How long should I wait to place another?

Why do you think it failed? That helps determine the treatment rationale.

Was the site infected at the time of the placement surgery? Did you adequately sanitize the site? Did you over heat the bone when prepping the osteotomy? Did you strip the bone when placing the subsequently placed implant? These are the basic questions as per early failure. As to when to revisit. Graft and renter at 4 to 6 months. Longer is better.

Should have placed one size bigger diameter implant immediately, and grafted buccul aspect if bone was less than 3 mm, seems you dint have primary stability at 1 st surgery and if extraction was done you used final diameter drill

Thank you everybody for your comments, I think the implant failed for a number of possible reasons, the patient had periodontal problems with severe bone loss, infected pockets,etc. Before the surgery the patient had a cleaning and scaling done and was place on antibiotics.The sites of extraction were curetted, I don't think I over heat the bone , the osteotomy was small ( just went 3-4 mm apically from the socket and have good stability at the moment ) At the site of one of the failed implants, the buccal plate was thin but I grafted it, also an immediate denture was delivered and few days later was adjusted exactly at the site of that implant. So I think here, there were few things that went wrong and I failed to forecast.

Evaluate the implant by I.O.P.R if no radiolucencies I suggest to retighten the implant and leave it 3 months under observation monthy x-ray if resorption seen evaluate extend may remove and GBR with insertion large diameter

Remove the implant and replace it at the same sitting after debriding. This is provided that you can place a wider diameter implant or a longer one so as to achieve primary stability and that you have adequate perimeter bone. Immediate replacement has less morbidity, less time investment and because of RAP phenomenon there will be accelerated healing.