20 Clinical evidence and Science Seal of the CONELOG® implant-abutment connection Harder et al. (2012) investigated in-vitro, the leakage of bacterial endotoxins from conical implant-abutment connections in two implant systems (Straumann Bone Level, CONELOG®) (8). The test specimens were inoculated with endotoxin and submerged in human whole blood. Endotoxin leakage was assessed in terms of changes in gene and protein expression involved in inflammatory processes in the blood cells. With both implant systems, leakage could be demonstrated even under unloaded conditions. The authors concluded that based on the study results, the prevailing opinion of a good sealing capacity with conical implant-abutment connections should be reconsidered. Further research with synchrotron radiography by Wiest et al. (2018) with the aim to validate a finite-element simulation revealed microgap formation with CONELOG® implants under loading (9). In all load applications with a force from the side it could be shown that the abutment is canted within the connection leading to gap formation. This study will be used as basis for investigating the impact of specific parameters such as screw pre-load on the micromovements since first modelling showed that the preload or screw mounting force has limited influence on microgap formation. KEY TAKE OUTS: SEALING PROPERTIES OF IMPLANT-ABUTMENT CONNECTIONS In general, butt-joint and conical connections all showed microgaps and micromovements allowing the penetration of bacteria irrespective of the connection design. The CONELOG® and the CAMLOG® implant-abutment connection, however, showed good sealing properties in studies. Therefore, both connections seem to be resistant to bacteria penetration which could also be shown in limited bone resorption over time in various clinical studies (refer to chapter: Clinical evidence for CAMLOG® and CONELOG® implants). 24.300 6 7 6 7 6 N = Screw Vent Camlog Replace Select Frialit-2 Brånemark 1.200.000 1.000.000 800.000 600.000 400.000 200.000 0 172.800 43.200 345.600 64.800 System Chewing cycles Fig. 14_Box plot diagram showing the chewing cycles reached before microbial leakage occurred in the individual systems. … median value. * extreme value. The CAMLOG® Implant System clearly reached the highest mean number of cycles among the tested systems (adapted from Steinebrunner et al. 2005) SCIENCE BEHIND THE IMPLANT-ABUTMENT CONNECTIONS
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