Immediate implants covered with connective tissue membranes: human biopsies

Osseointegration has been shown to occur around implants placed immediately after tooth extraction in humans. To date, such osseointegration has been achieved only with titanium plasma-sprayed (TPS) implants placed in extraction sockets with a bone-to-implant distance of less than 2 mm. In a previous report, when this horizontal defect dimension (HDD) exceeded 2 mm, the resulting percentage of bone-to-implant contact was reduced, indicating that the immediate technique would be limited in most cases to non-molar teeth. In an attempt to improve the bone-to-implant contact and the initial bone-to-implant contact in a vertical dimension, the implant surface, the type of membrane, and the method of membrane placement used in a previous study by our group were modified.

Ten large-grit sandblasted, acid-attacked (SLA) titanium implants were placed into immediate extraction sites in 5 patients. HDDs of 0.0 to 1.5 mm (controls), 1.5 to 4.0 mm, and >4.0 mm were used. Following insertion, implants were completely covered with a connective tissue membrane. This was in contrast to the use of an expanded polytetrafluoroethylene (ePTFE) membrane penetrated by the neck of the implant in our previous report. Primary closure of soft tissue flaps was achieved in each case. Six months after placement, 7 of the implants were histologically examined.

Osseointegration occurred across all HDDs, with the percentage of bone-to-implant contact in the 0.0 to 1.5 mm HDDs similar to that seen in the >4.0 mm HDDs. The first bone-to-implant contact measured vertically was similar in both the smaller and larger HDDs.

Osseointegration was successful in immediate implant placement sites with horizontal defect dimensions wider than 4 mm in humans when SLA titanium implants were completely covered with connective tissue membranes. It remains undetermined whether the different type of membrane, placement of the membrane, type of implant surface, or a combination of these 3 factors were responsible for the improved osseointegration in HDDs >4 mm. Further study is needed.