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Prediction of Narrow Implant Fracture Using Three-Dimensional Finite Element Analysis Compared with Fatigue Testing.
Introduction: Narrow diameter implants (NDIs) have been widely used in areas with limited space. However,
due to their smaller diameter, NDIs may have an increased risk of mechanical failure. The objectives of this
study are to evaluate the fatigue resistance and modes of failure of NDIs, as well as to compare the resulting
stress concentration using 3D Finite Element Analysis (FEA).
Method: Ten sets of NDIs (3.5x10 mm) abutments and stock abutments were prepared. Crowns were
cemented onto the stock abutments. Fatigue testing was conducted in accordance with ISO 14801:2016. The
specimens were subjected to stepwise loading at a frequency of 20 Hz, starting with a load of 200 N for 5,000
cycles, followed by 400 N, 600 N, 800 N, 1,000 N, and 1,200 N, each for 30,000 cycles. The failure load,
number of cycles, and modes of failure were recorded. Two specimens were analyzed using micro-computed
tomography before and after fatigue testing. Virtual models, simulating the samples from fatigue testing, were
constructed for FEA. A static load of 200 N and a fatigue load replicated experimental conditions, were applied.
Von Mises stress and damage were calculated, and the results from the FEA were compared with the
observed modes of failure.
Results: The failure load for the NDIs was 960 N, with a total of 92,165 cycles recorded. All specimens
exhibited fracture at the fixture and abutment screw. Fractures in the fixtures occurred horizontally at the
simulated level of the crestal bone. The maximum von Mises stress observed on the fixture, abutment, and
abutment screw were 423.8 MPa, 354.4 MPa, and 202.3 MPa, respectively. The areas of stress concentration
were analyzed in relation to the mode of failure. Damage accumulation indicated that fractures initiated on the
tensile side of the fixtures, which aligns with findings from micro-computed tomography.
Conclusion: All specimens failed due to fracture at the fixture and abutment screw. The results from fatigue
testing and FEA were comparable. Thus, FEA can be used to predict the location of crack initiation from fatigue
testing.
Keywords: Narrow Diameter Implant, Mechnical Failure, Fatigue Test, Finite Element Analysis