Evaluating the microgap and sealing capability in four implant systems with different interlockings under different tightening torques: an in-vitro study.

Purpose: This study assessed the microgap width and adhesion of three bacterial species in four dental implants with different interlocks under four screwing torques.

Materials and methods: Ten samples of four implant systems with various interlockings, including full-hexagonal (FHI), cylindrical-conical trilobe-index (TLI), Morse-taper with octagon terminal index (OI), and hexagonal interlock (slip-fit) (HI-SF), were used. The abutments were screwed to the fixtures under torques of 10, 20, 30, and 40 Ncm. The microgap between the abutment and the platform was assessed using a Scanning Electron Microscope (SEM). The leakage of 3 bacteria, including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, was evaluated under 30 Ncm torque.

Results: The TLI system showed the widest gap under all torques compared to others. There was no significance among all systems under different screwing torques. Regarding the leakage, there was no adherence to E. coli and S. aureus and 36.4% of Ps. aeruginosa to the HI-SF, followed by the OI system. The FHI and TLI systems showed the highest bacterial adherence.

Conclusion: Even with low torque, the studied systems showed gap widths narrower than acceptable width. Implant systems with FHI and OI demonstrated misfits of less than 2 µm upon 10 Ncm and less than 1 µm when the torque increases, giving them priority to be used in areas with poor bone quality. The HI-SF demonstrated a high ability to resist the adherence to E. coli and S. aureus, followed by OI. However, Ps. aeruginosa demonstrated a high ability to adhere to all systems.