Implants with external hexagon and conical implant-abutment connections: an in vitro study of the bacterial contamination

Abstract Prevention of microbial leakage at the implant-abutment junction is a major challenge for the construction of two-stage implants in order to minimize inflammatory reactions and to maximize bone stability at the implant neck. The aim of the present in vitro study was an evaluation of the leakage observed, over a period of 28 days, in Cone Morse taper internal connections and in screwed-abutments connections. In the present study ten specimens of Cone Morse (Group 1) and ten of internal hexagon (Group 2) implants were used. The inner parts of five implants, per group, were inoculated with Pseudomonas aeruginosa (PS) suspension and five implants, per group, with Aggregatibacter actinomycetemcomitans (AA). The possible penetration of bacterial suspension into the surrounding solution was determined by the observation of turbidity of the broth. In Group 1, bacterial contamination was found in three out of five implant-abutment assemblies seeded with the PS and in two samples out of five in the assemblies seeded with AA, with a total of leaked assemblies in this group of 5 out of 10. In Group 2, bacterial contamination was found in 4 out of 5 implant-abutment assemblies seeded with the PS, and in 4 out of 5 samples seeded with AA, with a total of leaked assemblies of 8 out of 10. The present data confirm the reported high permeability to bacterial leakage of screw-retained abutment connections, and the lower infiltration rates, although not significantly, of Cone Morse taper internal connections.