• Regular prestraining shows no reduction in bending fatigue life of Cp-Ti implants. • SWT-based analysis predicts fatigue life quantitatively within a factor of two. • Mode I crack propagation at the inner hole dominates the failure mechanism. Early fatigue fractures have been reported in type II thyroplasty implants made of commercially pure titanium (Cp-Ti), despite the known fatigue resistance of this material to prestraining. This inconsistency between clinical evidence and mechanical expectations highlights the need for validation of bending-induced prestraining effects. In this study, the influence of standardized prestraining on the fatigue performance of Cp-Ti implants was examined. A custom-designed jig was developed to relocate the bending fulcrum away from the stress-concentrating hole, ensuring accurate and repeatable formation. Three-point cyclic bending tests and fractography demonstrated that regular prestraining does not decrease fatigue life or alter fracture morphology. Elastoplastic finite element analysis showed consistent crack initiation at the inner hole on the tensile side of the superior wing, coinciding with the maximum stress concentration. Fatigue life predictions using the Smith-Watson-Topper (SWT) parameter, calibrated with cyclic stress-strain data, agreed with experiments within a factor of two. These results provide the first experimental and numerical clarification of fatigue failure mechanisms previously unresolved in clinical practice. The validated framework offers engineering evidence to guide implant preparation and identify the causes of premature fatigue fracture. Furthermore, that improve long-term reliability of Cp-Ti implants for the treatment of adductor spasmodic dysphonia (AdSD).
TOYOBA et al. (Sun,) studied this question.