Fatigue resistance of a new conical-hexagonal connection implant system

OBJECTIVES Fractures and structural failures of endosseous implants can severely compromise the implant-prosthetic rehabilitation plan, resulting in significant biological and economical damage. The risk of such events is particularly high when using implant systems of reduced diameter[1] or of poor design quality. The aim of this in vitro study is to evaluate the fatigue resistance of a newly designed implant screw featuring specific design enhancements. MATERIALS AND METHODS Twenty-seven slim implants, 3.4 & times; 8 mm, were characterized under static loading and subsequently subjected to fatigue cycling in air and in saline solution in accordance with ISO 14801:2016. Survival or failure events of the implant system were recorded in relation to the number of cycles. In cases of failure, optical and scanning electron microscopy were employed to determine fracture patterns and compare them with data obtained from the finite element analysis (FEA) performed during the design phase. The cyclic forces applied in the tests were compared with masticatory forces reported in the literature, in order to derive potential clinical implications useful to practitioners. RESULTS The static load analysis revealed a yield limit of 403 +/- 6.7 N and a maximum load of 727 +/- 9 N . Fatigue tests conducted in both dry conditions and physiological saline solution placed the fatigue limit be-tween 200 and 210 N. The two failures, which occurred as fractures of the implant at the level of its emergence from the support simulating the bone level, confirm the locations of maximum stress predicted by the FEA. CONCLUSIONS Despite its reduced diameter, this implant system, combining a hexagonal connection with a conical one, has demonstrated excellent performance under cyclic loading. Even under conditions simulating a 40% loss of the implant's length due to bone resorption, the load-bearing capacity remains well above 50% of the system's elastic limit and exceeds the load reasonably expected during clinical function. CLINICAL SIGNIFICANCE The high level of resistance to static load and cyclic fatigue relative to the elastic limit, together with the comparison of the obtained values to the masticatory forces reported in the literature, allows for the prediction that the system can withstand, with a substantial safety margin, the broad spectrum of functional stresses occurring in both the anterior and posterior regions of the dental arch.