Bacterial colonization of the implant-abutment interface using an in vitro dynamic loading model

Background: Previously, we demonstrated that the geometry of the fixture–abutment interface influences the risk of bacterial invasion into the internal part of the implant, although the contribution of loading on this invasion was not evaluated. The aim of the present study is to use an in vitro dynamic‐loading model to assess the potential risk for invasion of oral microorganisms into the fixture–abutment interface microgap of dental implants with different fixture–abutment connection characteristics. Methods: Twenty‐eight implants were divided into two groups (n = 14 per group) based on their microgap dynamics. Group 1 was comprised of fixtures with internal Morse‐taper connection that connected to standard abutments. Group 2 was comprised of implants with a four‐groove conical internal connection that connected to multibase abutments. The specimens were immersed in a bacterial solution of Escherichia coli and loaded with 500,000 cycles of 15 N in a wear simulator. After disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated, and cultured under appropriate conditions. The difference between loosening and tightening torque value was also measured. Results: One of the 14 samples in Group 1 and 12 of the 14 of samples in Group 2 developed multiple colony forming units for E. coli. Implants in Group 1 exhibited an increase in torque value in contrast to implants in Group 2, which exhibited a decrease. Conclusion: This study indicates that differences in implant design may affect the potential risk for invasion of oral microorganisms into the fixture–abutment interface microgap under dynamic‐loading conditions.