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Background.Using titanium alloys as an implant material has acheived a huge interest recently due to its high biocompatibility as well as stable fixation between implant and human bone. A finite element model is needed to design standard implants.The purpose of this study was to compare two types of dental abutments which are commonly used in screw-retained restorations under dynamic loading which can simulate masification forces and evaluate the influence of the implant-abutment connection design to prevent screw-loosening, abutment fracture and implant failure. Methods.First a a high-quality scanner was used to model an implant with Oneand two-piece dental implant abutments which were placed on each in Abaqus software version 6.14.All the components of the system were presumed linear elastic, homogenous and isotrpic.After loading (250 N vertical force with 4 Hz frequency), von Mises stress was recorded. Results.The maximum stress in one-piece abutment body was less than two-piece one (91 Mpa vs. 142 Mpa).In addition the maximum stress value in the last thread of the screw of two-piece abutment was significantly higher than the body of two-piece abutment (424 Mpa vs.142 Mpa). Conclusion.Occurance of stress concentration in the last threads of two-piece abutment leads to screwloosening, fracture of the screw from the threads and finally prostheses’ fracture. Although integrated screwed-in abutments are highly resistant to screw-loosening two-piece abutments are better clinical choices considering less stress concentration developed in bone. The phenomenon of screw-loosening helps the clinician to recognize over-loading and lets them prevent catastrophic mechanical failure of the implant and fracture of the peri-implant bone.

Comparing one- and two-piece dental abutments under dynamic loading: A 3-D finite element analysis