Fracture Surface Analysis of Implants with Fatigue Failure

Dental implants have become increasingly important in oral rehabilitation. However, implant treatments still frequently fail. Fracture or loosening is most likely to occur in the screw, and it may be caused by a specific chewing behavior of the patient. After implant failure, secondary surgeryfor reimplantation is almost always necessary. If a dentist fully understands the problem, a risk of secondary failure of the implant still exists. A reliable method for dentists and manufacturers to evaluate the mechanisms of implant fracture is still unavailable. To provide an indicator for assessing the fracture mechanisms of fracture abutment screws, a fractographic analytical technique was used in this study. Tested implants were loaded with a cyclic force. The fracture surfaces of failed screws were observed, and their SEM images were recorded. Our results showed that 2 fracture phases, i.e., a smooth phase region and rough phase region, could be observed on the fracture surface. After identifying the interface between the 2 phases, the ratio of the smooth phase region to the entire surface was calculated. The smooth phase ratios were 77%, 68%, and 61% when the tested implants were subjected to dynamic loadings of 50%, 55%, 61% UFL, respectively. Linear relationships were found between the smooth region ratio and loading magnitude (R2 = 0.8506, p < 0.01). These results demonstrate that fractographic analysis of the fracture surfaces of the failed implant has the potential to become a useful indicator for assessing implant fracture mechanisms. The method presented in this study can serve as an important reference for future advanced in vivo studies.