Dental implants with locking taper connection versus screwed connection: microbiologic and scanning electron microscope study

The aim of this study is to carry out an analysis of the Fixture-Abutment Interfaces (FAI), comparing different connection systems, to evaluate the role of geometric discrepancy, which is present between the abutment and the fixture, in favoring the permeability to bacterial colonization. Two types of commercially available FAI were studied, 16 screwed FAI (Sweden-Martina Italia) (4 of Ø 3.8 mm diameter, 4 of Ø 4.7 mm diameter, 4 of Ø 5.7 mm diameter and 4 of Ø 6.7 mm diameter) and 4 FAI (Bicon) (Ø 3.5mm diameter). The assays were carried out in vitro, placing the different dental implants in contact with broth culture of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Streptococcus pyogenes to test the infiltration inside the FAI. Furthermore, scanning electron microscope (SEM) analysis was carried out to evaluate the gap at the fixture-abutment interface. In all the locking taper FAI and in the screwed FAI with a diameter of 3.8 mm there was no trace of bacterial infiltration of the species examined. In the screwed FAI with a diameter of 4.7 mm, 5.7 mm and 6.7 mm there was an increasing level of bacterial infiltration in relationship to the diameter. Therefore, this paper shows that there exists an important correlation between the diameter of the screwed implant and the permeability to microbic infiltration that is directly proportional to the diameter of the implant.