Abstract
Fatigue is the most common mechanical failure type in dental implants. ISO 14801 standardizes fatigue testing of dental implants, providing the load-life curve which is most useful for comparing the fatigue behavior of different dental implant designs. Based on it, many works were published in the dental implant literature, comparing different materials, component geometries, connection types, surface treatments, etc. These works are useful for clinicians in order to identify the best options available in the market. The present work is intended not for clinicians but for dental implant manufacturers, developing a design tool that combines Finite Element Analysis, fatigue formulation and ISO 14801 experimental tests. For that purpose, 46 experimental tests were performed on BTI INTERNA® IIPSCA4513 implants joined with INPPTU44 abutments by means of INTTUH prosthetic screws under three different tightening torque magnitudes. Then, the load case was reproduced in a FE model from where the nominal stress state in the fatigue critical section was worked out. Finally, Walker criterion was used to represent accurately the effects of mean stress and predict fatigue life of the studied dental implant assembly, which can be extended to most of the products of BTI manufacturer. By means of this tool, dental implant manufacturers will be able to identify the critical design and assembly parameters in terms of fatigue behavior, evaluate their influence in preliminary design stages and consequently design dental implants with significantly better fatigue response which in turn will reduce future clinical incidences.
Highlights
Dental implants are used to restore completely edentulous jaws as well as single missing tooth [1].Single restorations are usually formed by a dental implant along with a prosthetic abutment, and both components are joined by means of a prosthetic screw as illustrated in Figure 1 [2]
The load case is reproduced in a Finite Element model of the dental implant, in order to obtain the variable forces acting on the prosthetic screw during the test, from where the nominal stress state of the critical section will be calculated
Fatigue failure is a major mechanical problem in dental implants, where the screw thread section is the most common failure section according to specialized literature
Summary
Dental implants are used to restore completely edentulous jaws as well as single missing tooth [1]. Clinical studies report that the vast majority of implant restoration mechanical failures are caused by fatigue [8]. These failures can take place in the abutment, in the implant body or in the prosthetic screw depending on implant diameter, load case, implant position, etc. A cyclic load must be applied to the dental implant assembly in a direct stress fatigue test bench. F-N curves are not useful for predicting the in vivo performance of a dental implant, but for comparing dental implants of different designs, sizes, or assembly conditions in terms of fatigue response.
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