Evaluation of resistance against bacterial microleakage of a new conical implant-abutment connection versus conventional connections: an in vitro study

The aim of the present in vitro study was to evaluate bacterial microleakage from inside to outside the implant-abutment assembly in a new design of internal conical connection compared to eight different internal connections. The design of this connection should prevent or limit microbiologic leakage into the surrounding implant tissue, that could contribute to infections without bone loss (mucositis) or with bone loss (peri-implantits). In order to investigate bacterial microleakage, the inner part of each system was inoculated with an Escherichia coli suspension. Eight different groups were considered; each group was composed of 10 dental implants, for a total of 80 implants. Groups 1-7 were considered controls, while group 8 was the test connection (an internal connection characterized by a double taper principle). Results showed that in control implants (Group 1 to 7), little microleakage was observed after the first 6 hours (500 CFU/ μl) and, after 24 hours of incubation, they showed a significant bacterial contamination in all samples (>100.000 CFU/ μl). In group 8 (test connection) no contamination was found in the first 6 hours, with 7 out of 10 implants showing no contamination even after 96 hours. Statistically significant differences were found between Group 8 and the other groups (p<0.05), whereas no significant differences were found among implants of the control groups (from group 1 to 7). Within the limits of the present study, the new connection studied presented significantly less microleakage at 96 h in comparison with the other control internal connections.