Load Fatigue Performance of Implant-Ceramic Abutment Combinations

The mechanical properties and functional load performance of implant-metal abutments combinations have been studied widely. However, the rotational load fatigue performance of the newly introduced ceramic implant abutments has not been reported. Objectives: This study investigated the load fatigue performance of four implant systems and their corresponding zirconia abutments at manufacturer's recommended torque levels. Methods: 3 diameters (Narrow, Regular, Wide) of Replace Select (RS) and Branemark (BM) systems (Nobel Biocare (NB)) and 2 diameters (4.1mm, 5.0mm) of Osseotite-NT (3i.E) and Osseotite-NT Certain (3i.C) systems (Implant Innovations (3i)) were used to constitute 10 implant–abutment test-groups. The abutments tested were Procera-zirconia (NB), Zireal-posts and Certain-ZiReal-posts (3i). n=5. A rotational load fatigue machine applied a sinusoidally varying tensile-compressive 21N load to specimens at a 45⁰ angle to produce an effective bending moment of 35Ncm at test frequency 14Hz. The number of cycles to failure was recorded with the upper limit set at 5x10⁶ cycles. Results: Abutment fractures were observed in narrow, regular and wide diameter groups of NB systems and in the 4.1mm groups of 3i (4,7,2 and 5 specimens respectively for total 18 events). Implant fractures were recorded for RS narrow and regular diameter groups and 4.1mm 3i.E (3,3, and 1 specimens respectively). Damage of implant platform was observed predominantly in BM groups. Abutment screw fractures were recorded for Goldtite (3i), Torqtite and titanium(NB) screws (6,4 and 6 specimens respectively). 29 out of the total 50 specimens failed (58%). 2-way ANOVA revealed no significant difference between the implant systems but significant differences between diameters. Subsequent 1-way ANOVA revealed statistically significant differences between the 10 implant-abutment test-groups. Conclusions: Rotational load fatigue performance of zirconia abutments is dependant on the cross-sectional dimension. Implant, abutment and screw failures were all observed. Failure mode varied according to system-specific design characteristics.