Leakage of microbial endotoxin through the implant-abutment interface in oral implants: an in vitro study

Abstract

In conventional two-piece implant systems, the abutment is connected to the implant mechanically via a screw. This creates an interface throughwhich leakagemay occur. In 1977, the first dental implant was designed by Br˚anemark et al. and wasmanufactured for human implantation and consisted of a screwretained slip-fit butt-joint external hexagon connection [1]. The external hex connection was the first connection design and was used primarily as a carrier of the device into the mouth [1]. The external implant-abutment connection however does present with severalmechanical and biological complications such as screw loosening, rotational misfit at the implant-abutment interface, and microbial penetration [2]. Implant-abutment connections have evolved greatly in an attempt to minimize these complications. Leakage however is not isolated to external connections and may occur in internal connection designs as well; however, the quantity of leakage is unknown in both design types. In 1986, one of the first internal implant-abutment connections was developed by Niznick [3].This connection was designed with a 1.7mm deep internal hexagon connection below a 0.5mm wide 45- degree taper which proved to have superior force distribution properties when compared to the original external hexagon Hindawi Publishing Corporation BioMed Research International Volume 2016, Article ID 9219071, 6 pages http://dx.doi.org/10.1155/2016/9219071 2 BioMed Research International implant-abutment connection [2]. Since then, several variations of the internal and external implant-abutment connection were developed in an attempt to outperform previous designs. These include internal spline connections, Morsetaper connections, and Internal Octagon connections [3]. Theimplant-abutment interface acts as a reservoir for oral microorganisms [4, 5] that in turn may induce an inflammatory response within the peri-implant tissues with a resultant loss of peri-implant crestal bone [6, 7]. As a result, studies [8] were conducted on the tightness of implant-abutment connections against corpuscular bodies (viable bacteria). In 2010,Harder et al. suggested that themere ingress of bacterial endotoxins (requiring less of a micro gap) was enough to initiate the inflammatory cascade and tissue destruction that leads to peri-implant bone loss [9]; this concept was demonstrated by Hou et al. in 2013 [10] by the upregulation of osteoclasts by bacterial endotoxins. In Harder’s study of two internal implant-abutment connections, he showed one to leak after only 5 minutes whilst the hermetic seal of the other remained intact after 168 hours. This study suggests vast variation in performance of implant-abutment connection seal even within design categories. Research Motivation. Failure of the implant-abutment hermetic seal may lead to crestal bone loss and peri-implant disease, eventually leading to implant loss. A comparative performance analysis between current connections may highlight superior connection designs for future implant selection and planning. Aim.The aimof this studywas toinvestigatewhether there is a difference in the ability of current implant connection designs to limit the movement of microbial endotoxins across the implant-abutment interface. If leakage does occur, we will, in addition, aim to quantify it and hence compare the various IACs implicated in this study. [No abstract provided. Information taken from introduction]