Wiskott, H. W. Anselm

Purpose: 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. Materials and Methods: 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. Results: 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. Conclusions: (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. Keywords: connectors, dental implants, failure, fatigue

Purpose: Microstructural analyses of commercially pure titanium (CpTi) are scarce. The present report presents the micrographs, fractographs, elemental characteristics, and hardness profiles of brazed joints and weldments using machined rods of CpTi. Materials and Methods: CpTi rods were joined using four techniques: laser welding, electric-arc welding, electron-beam welding, and gold- and Ti-filler brazing. The specimens were then subjected to tensile and fatigue loading. After sectioning and patterning, optical micrographs of intact joints were obtained. Fractured surfaces were investigated using scanning electron microscopy (SEM). The joints composition was determined by SEM-energy dispersive x-ray analysis. Hardness was determined at specific locations using a microindenter. Results: While laser welding left the parent metals equiaxed structure fairly intact, electric-arc welding, electron-beam welding, and brazing created a heat-affected zone in the vicinity of the joint. The extent and characteristics of the heat-affected zone depended on the amount of heat transferred to the specimens. In this respect, brazing essentially increased grain size and altered their shape. Electron-beam welding augmented this phenomenon, yielding grains that encompassed the full diameter of the joint. Electric-arc welding disrupted the granular pattern and generated highly lamellar/acicular structures. Conclusion: Hardness was not a good indicator of mechanical resistance, nor was the joints structural continuity with the parent substrate. Still, acicular microstructures were characterized by a peculiar behavior in that such joints were highly resistant to tensile stresses while their fatigue strength ranged among the lowest of the joints tested.