Sealing capability of implant-abutment junction under cyclic loading: a toluidine blue in vitro study

The aim of the present in vitro study was to evaluate the leakage observed in external hexagon (EH) and cone Morse (CM) tapered implant-abutment connections, using toluidine blue.

A total of 60 implants, 30 with a screw-retained EH abutment and 30 with a CM taper internal connection, were used. Toluidine blue was placed into the deepest portion of the internal compartment of the 2 different implant systems, and cyclic loading was applied for each group as follows: 10 samples underwent 1 × 10⁶ loading cycles, 10 samples underwent 3 × 10⁶ cyclic loading and the least 10 samples underwent 6 × 10⁶ cyclic loading.

No significant differences between the EH and CM groups were detected when the lowest loading cycles were applied (p = 0.2624), while differences were found when the samples were loaded with 3 x 10⁶ and 6 x 10⁶ cycles (p = 0.00124), with significantly lower toluidine leakage in CM group.

In conclusion, the results of the present in vitro study demonstrated that flow of the toluidine blue to the external portion of the implant-abutment assembly occurred in both types of implant-abutment connections, with very different percentages. Indeed, the CM taper internal connection seems to be more resistant to the leakage of dyes when compared with EH connections.