Investigation of Implant Stability Quotient Values of Dental Implants Placed in Vascularized Bone Grafts

Vascularized autologous bone grafts are widely used for mandibular reconstruction. There have also been numerous reports of occlusal reconstruction by placement of implants in the grafted bone following reconstruction of the mandible. However, the histological structure of the bone used for the graft is different from that of healthy mandibular bone, and the osseointegration process of implants placed in grafted bone is not clear. In this study, implants placed in reconstructions using grafted bone were assessed by measuring the implant stability quotient (ISQ), and their values were compared to those from implants in healthy mandibular bone. The subjects were 5 implants placed in the sites of mandibular reconstructions with vascularized fibula flaps. The controls were 54 implants placed in the molar region of healthy mandibles. All implant placements were carried out by a two-stage procedure, and the ISQs were measured at first-stage surgery and at second-stage surgery. The ISQ values thus obtained and the change in ISO from first-stage surgery to second-stage surgery were examined statistically. There was no significant difference in the ISQ between the two groups at first-stage surgery, but the values of the ISQ and the change in ISQ were significantly greater in the mandibular reconstruction at second-stage surgery. This appears to be the result of histological differences between the reconstruction site and the healthy bone. The ISQ is an objective index of osseointegration of the implant. The present results suggest that observing changes in ISQ over time allows investigation of the usefulness of different types of bone grafts for implant therapy.