Resistance of ITI implant connectors to multivectorial fatigue load application

In an effort to provide patients with mechanically optimized implant connectors, this study was designed to assess the relative fatigue resistance of five types of connectors for the ITI implant system: (1) standard (screw-on) abutments torqued to 35, 70, and 140 Ncm; (2) metal Octa connectors torqued to 35 Ncm; (3) ceramic Octa connectors torqued to 15 and 35 Ncm; (4) cemented cast-on abutments; and (5) an experimental screw-retained composite core.

To duplicate the alternating and multivectorial intraoral loading patterns, the specimens were subjected to the rotating cantilever beam test. The implants, their connectors, and abutments were spun around their longitudinal axes while a perpendicular force was applied to the external end. The objective was to determine the force level at which 50% of the specimens would survive 106 load cycles. The mean force levels at 50% failure and their 95% confidence intervals were determined using staircase analysis.

The fatigue resistances of the standard (screw-on) abutment, metal Octa connector, and ceramic Octa connector torqued to 35 Ncm were within a few percent of one another. The fatigue resistance of the cemented cast-on abutment was approximately half that of the screwed connectors, and the experimental screw-retained composite core's resistance was about 30%. Increasing the preload in the standard abutments and ceramic Octa connectors increased their fatigue resistance.

Preloaded screwed components were mechanically superior to cemented cast-on abutments and screw-retained composite buildups. For the screw-on connectors, augmenting preload (ie, torque) augmented the resistance to fatigue loading.