Nonlinear Stress Analysis of Titanium Implants by Finite Element Method

Abstract

With use of dental implants on the rise, there is also a tandem increase in the number of implant fracture reports. To the end of investigating the stress occurring in implants, elasticity and plasticity analyses were performed using the finite element method. The following results were obtained:(1) With one-piece type of implants of 3.3 mm diameter, elasticity analysis showed that after applying 500 N in a 45-degree direction, stress exceeding 500 MPa -which is the proof stress of grade 4 pure titanium -occurred. This suggested the possibility of fatigue destruction due to abnormal occlusal force, such as during bruxism. (2) With two-piece type of implants that can tolerate vertical loading of 5,000 N, plasticity analysis suggested the possibility of screw area fracture after applying 500 N in a 45-degree direction. (3) On the combined use of an abutment and a fixture from different manufacturers, fracture destruction of even Ti-6Al-4V, which has a high degree of strength, was predicted.

Impact of Intentional Overload on Joint Stability of Internal Implant‐Abutment Connection System with Different Diameter

“…In this study, up to 800 N of vertical loading was applied as an arbitrary maximum occlusal force for molars . Although previous in vitro studies have reported that varying implant/abutment connection systems exhibit sufficient joint strength to withstand heavy loading, the current study revealed that the overload condition resulted in some amount of axial displacement and preload loss, which might detrimental to sustain joint stability. Excessive occlusal load challenges the implant and its prosthetic components, which might lead to biomechanical complications.…”

“…No fracture failure or plastic deformation of the implant/abutment complex was detected after 500 N of cyclic loading; 500 N was adopted as an arbitrary overload condition imitating the functional environment of the second molar area . Several in vitro studies of implant cyclic loading adopted ISO 14801 test setup with worst‐case scenario and applied a relatively low loading condition, ranging from 50 to 150 N. Some in vitro and finite element model studies reported 500 N as the maximum failure strength of implants made of commercially pure titanium (cp Ti‐grade 4) that plastic deformation could occur under oblique loading . Unlike those studies, our study aimed to evaluate the overloading environment with maximized axial displacement.…”

“…In the second molar area, the average occlusal force has been reported to be 450 to 550 N, and maximum force to be up to 800 N in natural teeth . Adequate fracture resistance has been reported even under overloading condition in ICC systems . Nevertheless, implant‐supported single prostheses in posterior regions could be exposed to occlusal overload and have been reported to have a higher risk for mechanical complications .…”

Stress Distribution in Single Dental Implant System

“…31 The same can be said for the implant, which showed much higher stress concentration when submitted to oblique load. 32 Stress exceeding 1 GPa, which is larger than the proof stress of 900 MPa of Ti-6Al-4 V alloy, 29 was concentrated in the implant neck. The numerical results, however, might be influenced by the boundary conditions, once the surfaces were considered perfectly bonded and, thus, the abutment was not able to rotate and move away from the implant platform.…”

“…These findings are in accordance with other studies, which stated that oblique load is associated with higher stresses. 16,29 It is important to emphasize that oblique load application has been related to more realistic occlusal loading. 11 The abutment screw fracture is a frequent problem in the clinical field.…”