Degree of Bacterial Microleakage at the Implant-Abutment Junction in Cone Morse Tapered Implants under Loaded and Unloaded Conditions

Purpose Different results have been reported on the internal colonization of Cone Morse connections under in vitro dynamic loading. The aim of the present in vitro study was to evaluate the bacterial leakage in Cone Morse implant-abutment connections, both under loaded and unloaded conditions. Methods A total of 20 implants with a Cone Morse taper internal connection were used in this study. Ten were loaded under a special testing equipment (Test Group), while 10 were left unloaded (Control Group). The inner part of all implants was inoculated with 0.1 μl of a viable Enterococcus faecalis suspension. A force of 120 N was applied to the loaded implants, for a total of 500,000 cycles at 1 Hz. All the samples were checked daily, for a total of 14 days, and presence or absence of turbidity recorded. Results In the unloaded assemblies, bacterial contamination was found in 2 out of 10 implant-abutment junctions, on the 12th and 13th days. In the loaded implant-abutment connections, bacterial contamination was found in 2 out of 10 implant-abutment assemblies, on the 13th and on the 14th days. Conclusions The resistance of the Cone Morse implant-abutment junction reported in the literature and confirmed in the present study, where no differences in the percentages of microbial leakage were found in assemblies unloaded and in those subjected to a dynamic loading procedure, could help to explain the histological results in man of a lack of peri-crestal bone resorption in Cone Morse implants, placed below the level of the alveolar crest.