Implant–abutment connections: influence of the design on the microgap and their fatigue and fracture behavior of dental implants

Abstract

Microgap between implant and abutment can produce biological and mechanical problems such as peri-implantitis and/or fatigue failures. The aim of this study was to evaluate microgap size and fatigue behavior of external and internal connections. In both systems the torque to tighten the abutment screw of single crown abutments was 45 Ncm. Fifty implants for each connection type were studied. One subgroup (n = 5) was used by the observation and evaluation of the microgap, other (n = 5) was tested for fracture strength and the other (n = 40) was subjected to dynamic loading. The internal connection presents a lower microgap than the external ones. From fatigue results, the external hexagon interface showed superior result compared to the internal hexagon interfaces. The tolerances in the internal connections are better and favour the fatigue behavior but this factor alone is not sufficient to improve the fatigue response in relation to the external connections when the screw is subjected at the same torque. The external system presents a higher value of the area than the internal and it produces a better load distribution. Microgaps and mechanical properties are very important for the long-term behavior of the dental implants and these aspects should be known by the implantologists.

Comparative study of compressive and fatigue strength of dental implants made of nanocrystalline Ti Hard and microcrystalline Ti G4

“…Regarding the thickness of different components, Gil et al . showed that thicker external hexagonal connections were usually able to provide a better load distribution because of its higher resistant section . This statement is in line with the discussion presented above.…”

“…Commercially pure titanium has good biocompatibility and is free of alloying elements that may be harmful to the organism, but has low mechanical strength. The possibility of implant failure is catastrophic because fracture of any implant component may compromise the long‐time performance of the device . From the patient perspective, implant failure compromises esthetical and functional recovery, with impact on self‐esteem and quality of life, respectively.…”

“…During oral activities, implants are required to support axial loads around 120 N . Apart from overloads, cyclic forces are also expected during chewing and biting.…”

“…Relevant implications for implant life are related to the ability of the implant–abutment junction to transmit the load to the structure during mastication efforts. The stress distribution upon implantable devices relies on the interface between hard tissue and the implant–abutment junction, but an overall approach seems reasonable, because the fatigue endurance of all components has a significant influence on the long‐term performance of the devices …”

Biomaterial‐based possibilities for managing peri‐implantitis

“…Conversely, even considering all benefits of the dental implant design evolution, interface microgap values under dynamic‐loading conditions, below bacteria dimensions, are still a challenge. Studies have shown microgaps for internal and external connection around 0.97 and 1.22 μm, respectively, that is, 5 to 6 times larger than overall bacterial size. With bacteria generally having a size of 0.2 μm in diameter and 1‐8 μm in length, this means that microbial penetration through this space is inevitable.…”