Evaluation of microgap with three-dimensional x-ray microtomography: Internal hexagon versus cone morse

Background: Microgap is defined as the microscopic space that exists between the implant body and abutment. The main mechanism proposed for microgap-related crestal bone loss is the role of this space as a trap for bacteria and thus, as a putative etiological factor for inflammatory reaction in the peri-implant soft tissues. The aim of this paper was to evaluate, with X-ray 3D microtomography, the microscopic space that exists between the implant body and abutment with internal hexagon versus cone morse. Methods: A total of 20 implants were used in this in vitro study. Ten implants per group were used. Ten implants presented a screw retained internal hexagon abutment (Group I) and 10 had a Cone Morse taper internal connection (Group II). Results: In both types of Cone Morse internal connection implants there was no detectable separation at the implant/abutment in the area of the conical connection, and there was an absolute congruity without any microgaps between abutment and implant. No line was visible separating the implant and the abutment. On the contrary, in the internal hexagon screwed abutment numerous gaps and voids were present between the implant body and abutment. Conclusion: The results of the present study seem, then, to support the hypothesis that the length and the characteristics of the implantabutment joint could be a reason for the observed differences in mechanical stability.