Biomechanics of self-loosening of the screw that connects the intraosseous part of the implant and the abutment with the orthopedic structure attached to it

Abstract

The results of the study of the stress-strain state in the elements of the system “intraosseous part of the implant - screw - abutment with an orthopedic structure fixed on it” under different given conditions of its functioning are presented. We have determined the stress-strain state in the crown neck area, which replaces the upper jaw central incisor, in the presence of the natural wear (0.5 mm) of the teeth and anthropoid teeth next to the implants and the same nine load variants as in the initial non-prosthetic model, i.e. a total of 54 calculation experiments have been carried out. It has been established that the occurrence of such secondary mechanical complication of dental implantation as loosening of the screw connection between the intraosseous part of the implant and the prosthetic structure fixed on the abutment influences the type of teeth clamping (bite), the angle of the preferential transfer of chewing load, the propensity and the wear ability of the teeth. The most unfavourable, in terms of the value of the torque that unwinds the fixation screw, is the direct occlusion of the teeth and the angle of the preferential load transfer of 1450 (Mpr = 1.16 Nm), or 3.87% of the twisting torque value. At the same conclusions of the set parameters and the value of erosion of its teeth 0.5 mm the value of the torque, which untwists, increases by 5 times and corresponds to 19.3% of the initial torque (30 Nm) and will inevitably lead to its untwisting.