The Branemark screw type titanium fixture has an external hex (0.7mm) that has many inherent problems during implant placement and requires an additional surgery. Problems also arise during prosthetic transfer, and in use of multiple abutments, the abutment/implant interface results in screw loosening and prosthetic complications. An extension of this external implant hex to 3mm in height provided a solution to these problems.
The 3mm hex extension was designed specifically to protrude the oral mucosa during the three-month healing period, with no second stage surgery required. Eight years life table analysis indicated no significant difference in survival between two-stage (91.6 %) and the one-stage (89.7%) P>0.05. A total of 172 consecutive patients with more than 800 implants over a period of 96 months were evaluated.
This 3mm extension provides a stable support for the final prosthesis, hence no abutment is necessary. The removal of the abutment implant interface eliminates all prosthetic complications. A prefabricated, castable coping matching the external hex of the extension can be used as transfer, tissue spacer and as prosthetic coping for the final restoration.
A dynamic, functional comparative analysis of a screw retained versus cement retained prosthesis cemented at this hex extension, oscillating at 24º at 0.02Hz at 15kg resulted in the following: the cement group failed on average at 2.6 M cycles (SD=2.27M cycles) for n=20, and screw retained samples failed at 2.17 M cycles (SD=1.27M cycles) when n=18 (P>0.05).
Thus, using implants with a 3mm external hex eliminates all but 6 components in the restoration of single tooth replacement to an edentulous maxilla fixed-detachable type of restoration.
1. Bernard J-P, Belser UC, Martinet JP, Borgis SA.: Osseointegration of Branemark Fixtures Using a Single-step Operating Technique. A Preliminary Prospective One-year Study in the Edentulous Mandible. Clin Oral Implants Res 1995;6:122-129.
2. Preiskel HM, Tsolka P. Telescopic prostheses for implants. Int J Oral Maxillofac Implants 1998; 13:352-357.