Resistance of internal-connection implant connectors under rotational fatigue loading

To aid in developing mechanically optimized implant-abutment connectors, the fatigue resistance of 5 connector configurations of the Replace Select system (Easy abutment, Easy abutment without antirotational mechanism, Multi-unit abutment, Esthetic Alumina abutment, Esthetic Zirconia abutment) was investigated. Other purposes of the study were to determine whether the connector's antirotational mechanism participates in fatigue resistance and to compare the results with previous data on Straumann connectors.

The repetitive, alternating, and multivectorial intraoral force pattern was reproduced by subjecting the test specimens to the rotating cantilever beam test. To this end, the samples were spun around their long axis while clamped into a revolving collet on one end and loaded normal to their long axis on the other end. The aim was to determine the load level at which 50% of the specimens survived and 50% fractured before 106 cycles. Means were determined using the staircase procedure. They were fitted with 95% confidence intervals for intergroup comparisons.

In the chosen testing configuration, 2 statistical groups emerged. The Easy abutments with and without antirotational mechanism were statistically similar, with mean failure loads in the 70 to 72 N range. Both ceramic and the Multi-unit abutments belonged to the second group, with mean failure loads in the 53 to 58 N range.

(1) The fatigue resistance of ceramic and the Multi-unit abutments was approximately 20% less than that of the Easy Abutments. (2) The antirotational mechanism did not participate in mechanical resistance. (3) The fatigue strength of the Easy abutment connectors was approximately 20% greater than the equivalent abutments in the Straumann system.