The implant-abutment interface is the surface where the dental implant and the prosthetic abutment connect. There is more than one type of implant-abutment interface and the one selected by the practitioner often depends upon the location of the implant and the type of prosthesis that will be attached. One possible implant-abutment connection option is the external hex. An advantage to this type of interface is its compatibility with many different implant systems. However, the external hex connection is known to experience a higher incidence of screw loosening, more rotational misfit, and a less adequate seal against microbes. Another interface option is the internal connection. Advantages to using an internal interface include a lower incidence of screw loosening, a more effective microbial seal, and better strength at the joints. Disadvantages to the internal implant-abutment interface include the fact that the bone is the weakest part of the implant rather than the retaining screw.