Microscopic Feature of Fractured Implant in Practical Dental Use

抄録

Patients suffer considerable pain from fracture of placed implants. In order to reduce the number of fracturing failures in future and to obtain a better understanding of fracturing, a fractured implant has been investigated by means of radiography, scanning electron microscopy and transmission electron microscopy from a metallurgical viewpoint. The blade type implant of Ti-5V alloy has a virgin microstructure of a low density of dislocation with a dispersion of fine precipitates. Further dislocations and twins are introduced into the implant due to repeated loading in use, resulting in possessing a large amount of lattice defects until fracturing. The dislocations are considered to assist calcium penetration and to bring about intergranular fracturing near the surface of the implant. Striations are extensively observed at a center portion of the implant, indicating that the fracturing is caused by fatigue. Microscopic investigations reveal that the fracturing is initiated by some elements such as calcium in saliva in accordance with high density of lattice defects and developed through the fatigue by repeated loading.