The present study focused on clinical and radiographic characteristics of staged implants placed in autogenous bone grafts covered by either a PRF membrane (PRF group) or a standard procedure (gold standard) involving coverage of the autogenous bone graft using a deproteinised bovine bone mineral and a resorbable collagen membrane (control group).

The PRF group demonstrated a high implant survival; however, two out of 13 implants were lost in the control group. The difference between the groups was non-significant, although implant survival in the control group to some extent differs from that reported in previous studies on survival of implants placed in bone grafts [12, 13]. One implant (first premolar, regular platform (4.3 mm), length: 13 mm) and the corresponding implant-supported crown were lost 20 months after final crown placement due to failed osseointegration. The reason for the implant loss remains unclear since no preceding biological complications were reported. The fact that the biopsy was taken from a relatively narrow bone block may have compromised the clinical outcome of the implant treatment, although none of the bone blocks were clinically loosened during the biopsy procedure. Harvesting of bone biopsies of larger autogenous bone blocks followed by implant placement has previously been described [37, 38], but no follow-up on implant survival has been reported. Another possible explanation for the loss of the second implant (central incisor, narrow platform (3.75 mm)) were problems with rotation of the ASC abutment in relation to the metal adaptor when tightening the abutment screw at the time of placement of the final crown. While counter-torqueing the abutment screw, the implant loosened and was finally lost. Only original components were used when fabricating the implant-supported crown, and the reason for the minimal rotation remains unclear.