# Static Bacterial Leakage in Different Conometric Connections: An In Vitro Study
## 4 Discussion
Cone-Morse connections have been recommended for single implants, fixed partial prostheses, and overdenture planning due to their great mechanical stability [1; 38; 39]. The implant-abutment interface design and features are proposed largely to reduce crestal bone stress. The importance of implant-abutment leakage should not be overlooked in the emphasis on stress distribution [1]. Regardless of the connection type, the implants need to be manufactured with a precise seal to avoid or reduce any inflammatory responses and damage to the soft and hard tissues, which can result in bone loss surrounding the implants [1]. The precision and the manufacturing process of implants and engineering parts, and the design of the type of connection, is of paramount importance. Since the manufacturing of these parts is not efficient, they can act as reservoirs of endotoxins, by-products, and bacteria, consequently resulting in the failure of implant treatment [36; 39]. [PERSON] et al. [21; 40] analyzed the effectiveness of bacterial sealing of different types of implant/abutment connections, including Morse-taper implants with solid (MT) or MT-passing screws (MTps). The latter showed a lower bacterial infiltration. Indeed, according to the same author [21], in comparison to a solid abutment, the passive screw design enables a better fit between the abutment and implant when the implant is loaded, which, over time, reduces microleakage. In addition, in our study, we found a certain lower bacterial contamination in Cone-Morse with passing screws in respect to those with solid abutment. However, no statistically significant results were found. A limitation of this study is represented by the fixation modality adopted for Group 2 of solid abutmentsin Cone-Morse connections. As explained in Materials and Methods, the manufacturer suggested to use a percussion with 200 gr of force by means of the use of a beaver compatible with the platform of the abutment. The expert clinician that screwed all connections tried to use the same force for all samples, but no modalities to verify the real force used during the abutment activation were available. This could have negatively influenced the performance of Group 2, and the manufacturer should consider the production of a calibrated beaver for this type of abutment. Due to the limited data available in the literature, the comparison of findings should be performed with caution, and other in vitro and in vivo studies should be performed on this topic in order to obtain information more adherent to clinical conditions. Another limitation of this study is that the evaluation was performed in static conditions, and that loading could interfere with the marginal gap and permit the passage of a higher quantity of bacteria, especially in Group 3, which is characterized by a higher angle of 18\({}^{\circ}\), respective to the Cone-Morse connections [18]. However, despite the use of modern implant and implant connection systems, and within the limitations of the study, it is still not possible to prevent the passage of microorganisms through microgaps, even if this passage does not always result in an infection and inflammatory response of the host.