Numerical analysis of a dental implant system preloaded with a washer

Gold screw loosening is a problem that frequently affects dental implants. The application of a preload has been the main means of preventing loosenin g. However, this measure has not been able to eliminate its occurrence. In this study the effect of a washer in a Branemark-type implant on the loosen ing conditions of the retaining screw was investigated using a finite eleme nt simulation. The simulation indicated that a washer may significantly inc rease the tolerance of a screw against loosening. This is accomplished by i ncreasing the tolerance of the implant against deformation. The addition of a customized washer to a dental implant system may offer a very simple and inexpensive solution for the persistent problem of screw loosening.