On implant integration in membrane-induced and grafted bone

Abstract

Bone augmentation may be required in situations of severe jaw bone resorption to be able to use oral implants for reconstruction of the edentulous patient. The use of barrier membranes, bone grafts or a combination of the two have been suggested for this pupose. However, little is known to what extent augmented bone contributes to implant stability. The aims of the research undertaken have been to investigate the integration of titanium implants in membrane-induced and grafted autogenous bone with special emphasis on implant stability. Two animal models were developed, one for the study of membrane induced bone augmentation at exposed threads of implants and one for the study of implant integration in bone grafts. Histomorphometry, resonance frequency analysis (RFA) and removal torque measurements (RT) were mainly used as evaluation techniques. Titanium microimplants were used in patients to obtain histology of the bone graft/titanium interface at different healing intervals. The outcome of a particular grafting technique and delayed implant placement was evaluated in one prospective and in one cross-sectional clinical study using RFA. Membrane-induced bone augmentation at titanium implants and beyond the skeletal envelope was predictably achieved. However, this bone did not significantly contribute to the implant stability. Simultaneous placement of titanium implants in onlay bone grafts resulted in significantly higher stabilty, compared to implants placed without a bone graft. The use of a barrier membrane prevented graft resorption as long the membrane was in place but did not improve implant stability. Delayed implant placement after primary healing of onlay bone grafts resulted in a significantly higher stability and a higher degree of bone-implant contact when compared to simultaneously placed bone grafts and implants. Clinically retrieved microimplants placed in a delayed approach showed a significantly higher bone-implant contact and amount of bone within implants threads as compared to simultaneously placed microimplants, irrespective of 6 or 12 months healing. The use of a Le Fort I osteotomy with interpositional bone grafts and delayed implant placement, showed acceptable long term results. The implant stability in these cases, evaluated with resonance frequency, showed an increase with time. In conlusion and with obvious limitation to the tested experimental conditions a) membrane-induced bone did not contribute to implant stability in the model studied; b) delayed placement of titanium implants is preferable when using autogenous bone grafts and implants; c) implant stability increases with time after a Le Fort I osteotomy with interpositional bone grafts and delayed implant placement.