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Sealing effectiveness against Staphylococcus aureus of five different implant-abutment connections.

PURPOSE
To compare the sealing effectiveness of four different implant-abutment connections against Staphylococcus aureus (S. aureus). The null hypotheses stated that there was no difference on sealing ability among the implant-abutment connections tested.


METHODS
Five diverse commercially available dental implants were used to investigate the degree of microleakage at the implant-abutment junction (IAJ): Group 1: Torque Type conical implant with double conic connection - TTc (Winsix); Group 2: Torque Type conical implant with Cone Morse connection - TTcm (Winsix); Group 3: Free Lock connection - K type implant (Winsix); Group 4: Internal double hexagon - OsseoSpeed; Group 5: Internal hexagon - Aadva Implant. Nine implants were tested in each group and one group was used as the negative control (Group 4). The abutments were connected to implants according to manufacturers' recommendations. All procedures involving connection and disconnection of implants were performed in sterile conditions in a laminar flow biological safety cabinet. S. aureus ATCC 6538, a methicillin susceptible reference strain, was chosen for the experiments to test the degree of microleakage. Statistical analysis was performed in order to find significant differences among the five groups regarding sealing capability of the implant-abutment connections tested. The recorded data were statistically analyzed.


RESULTS
One implant from Group 4 was excluded from the study because of the growth of a contaminant after 48 hours of incubation in all three wells (i.e. Paenibacillus pabuli, environmental Gram-positive bacteria). Wells A and B (i.e. wells where the samples were passed before being located in the final well C) of all other samples (n = 46) remained sterile over the 72 hours of incubation, indicating the lack of external contamination during implant-abutment connection. Similarly, no bacterial growth was observed in the five negative controls (i.e. one implant for each type), which had been inoculated with sterile saline and processed as the others. Bacterial microleakage was demonstrated with three samples, including one sample of Group 1, one of Group 3 and one of Group 5, in which growth of S. aureus in wells C after 48 hours of incubation was demonstrated (Table 1). No statistically significant difference between groups was noticed (P> 0.05).


CLINICAL SIGNIFICANCE
Within the limitations of the present in vitro model, the results obtained suggest a tendency toward a better sealing capability for conical connections and internal hexagon.