Collagen fiber orientation near a fractured dental implant after a 5-year loading period: case report

Fracture of an implant is one of the possible complications of dental implants. It is a quite rare event but of high clinical relevance. Nevertheless, it represents an important opportunity for evaluating the peri-implant bone-tissue response to implant overloading in human beings. The aim of the present study was a scanning electron microscopy evaluation of a screw-shaped implant retrieved because of fracture and a birefringence analysis of the tissue near the fractured implant. There was 1 fractured screw-shaped implant retrieved from a patient with a trephine bur, and it was processed for histology. The specimen was analyzed under both scanning electron microscopy and circularly polarized light microscopy. The scanning electron microscopy fractography analysis showed the typical signs of a fatigue-fracture, with large plastic deformations on the implant. The fracture seemed to start from the internal coil of the implant. Under circularly polarized light microscopy investigation, a bone-implant contact percentage of 81.6% +/- 1.5% (mean +/- standard deviation) was found. The amount of the transverse collagen fibers was of 68.3%, and the amount of the longitudinal collagen fibers was of 31.7%. The difference was statistically significant for z = 2.247 (P = 0.025). The fracture of the implant was most probably correlated to a fatigue of the material mainly associated to a lesion of the internal coil. The high level of bone-implant contact percentage was correlated to a predominant transverse collagen fiber orientation of the collagen fibers in the peri-implant bone.