Two-stage implant systems result in gaps and cavities between implant and abutment that can act as a trap for bacteria and thus possibly cause inflammatory reactions in the peri-implant soft tissues. These gaps between the components are inevitable, and their clinical significance has so far been mostly neglected by both manufacturers and clinicians. The aim of the study was to determine whether there is microbial leakage at the implant-abutment interface. Thirteen different implant-abutment combinations were subjected to an in vitro experiment, in which the penetration of bacteria (Escherichia coli) was observed for 10 assemblies of each type. All implant systems presented microbial leakage. When the Frialit-2 implant was supplied with a silicon washer, there were fewer c ases of leakage. The width of the marginal gap between the prefabricated components, measured with a scanning electron microscope, was less than 10 um in all systems.