Among the complications that can occur at dental implants, the fracture of any implant component is a relatively infrequent but clinically relevant problem. Because of their mechanical characteristics, small diameter implants are at higher risk of such complication. The aim of this laboratory and finite element method (FEM) study was to compare the mechanical behavior of a 2.9- and 3.3-mm-diameter implant with a conical connection under standard static and dynamic conditions, following the International Organization for Standardization (ISO) 14801:2017. Finite element analysis was performed to compare the stress distribution on the tested implant systems under a 300-N, 30° inclined force. Static tests were performed with a load cell of 2 kN; the force was applied on the experimental samples at 30° with respect to the implant-abutment axis, with an arm of 5.5 mm. Fatigue tests were performed with decreasing loads, at 2-Hz frequency, until 3 specimens survived without any damage after 2 million cycles. The emergence profile of the abutment resulted the most stressed area in finite element analysis, with a maximum stress of 5829 and 5480 MPa for 2.9- and 3.3-mm-diameter implant complex, respectively. The mean maximum load resulted in 360 N for 2.9-mm-diameter and 370 N for 3.3-mm-diameter implants. The fatigue limit was recorded to be 220 and 240 N, respectively. Despite the more favorable results of 3.3-mm-diameter implants, the difference between the tested implants could be considered clinically negligible. This is probably due to the conical design of the implant-abutment connection, which has been reported to present low stress values in the implant neck region, thus increasing the fracture resistance.
Keywords: Morse-taper dental implant-abutment connection; dental implants; fatigue testing; finite element analysis; narrow diameter implants.