Previous in vitro studies have shown that a mean gap of less than 4 µm between prefabricated crowns and implants of the Ha-Ti implant system is not a barrier to infiltration by Staphylococcus aureus. These studies confirmed earlier in vivo work showing that a multitude of oral microorganisms could colonize and infiltrate these gaps. In the present investigation, 30 Ha-Ti implant-crown assemblies were tested for bacterial leakage after the gaps were sealed with the chlorhexidine-containing varnish Cervitec. S. aureus leakage into the totally submerged test specimens was detected in 1 of 5 samples incubated for 4 weeks, while no leakage was detected in specimens incubated for 3, 5, 6, 7, and 8 weeks. When the sealed test specimens were partially submerged (that is, excluding the screw hole of the crown) and incubated for 3 to 11 weeks, none of the internal surfaces of the 30 test specimens manifested contamination. The clinical relevance of gap sealing in maintaining inflammation-free marginal mucosa and in achieving clinically successful treatment of peri-implantitis has yet to be determined. Schlagwörter: bacterial leakage, dental implants, prefabricated crowns