# Static Bacterial Leakage in Different Conometric Connections: An In Vitro Study
## 4 Discussion  
The presence of a gap at the interface between implant and abutment represents the first step of bacterial colonization and then biofilm consolidation, with the activation of an inflammatory infiltrate that could trigger marginal bone loss. The performance of the implant-abutment interface is of crucial importance for the long-lasting soft and hard  
Figure 12: Percentage of bacterial leakage in the three different concentric connections over 90-day observation period (Error bars = standard deviation). peri-implant tissues. Consequently, over the years, a tremendous number of different connections have been produced to reach the objective of \"zero infiltration.\" Many factors have been considered fundamental for the bacterial accumulation at the implant-abutment interface, like the type of connection, the contact area, the angle of the concentric connection, the presence of an antirotational system, and the materials used. In this study, for the first time, the evaluation of the bacterial leakage of three different concentric connections, two Cone-Morse, and one 18\({}^{\circ}\) of the same manufacturer with the outgrowth model [18] was performed. Through this classic methodology, it is possible to verify bacterial penetration of the implant-abutment connection. Although no significant differences have been found among the groups, Cone-Morse connections with solid abutments showed lower bacterial infiltration. In particular, samples of Group 2 seeded with _S. oralis_ showed no infiltration. On the contrary, _P. aeruginosa_ presented a higher capacity to infiltrate all the connections. Bacteria such as _Streptococcus oralis_ and _Pseudomonas aeruginosa_ can be easily found in situations like this, as they are highly abundant at implant sites and periodontal infections and may form biofilms and result in peri-implantitis lesions [20; 26; 27; 28; 29]. In this in vitro study, it was observed that the passage of _P. aeruginosa_ occurred in all groups, contrary to _S. oralis_, which was unable to infiltrate all the connections, confirming the results obtained in a previous study by [PERSON] et al. [4]. It is important to emphasize that _P. aeruginosa_ is a Gram-negative aerobic motile rod with dimensions ranging in size from 0.5 to 0.8 \(\upmu\)m by 1.5 to 3.0 \(\upmu\)m [30]. Almost all strains move using a single polar flagellum. However, some have two or three flagella. It can be highly pathogen and also resistant to many commonly used antibiotics, low concentrations of antiseptic, dyes, and high concentrations of salt [30]. On the contrary, _S. oralis_ is a Gram-positive facultative anaerobe spherical coccus with a diameter of 1-3 \(\upmu\)m. The ability of bacteria to pass the implant/abutment connection is not a consequence of being an aerobe, anaerobe, or facultative one, and it is not directly correlated with pathogeny. In our previous study, we compared the bacterial leakage of different connections by using _P. aeruginosa_ suspension and _Aggregatibacter actinomycetemcomitants_. The latter is anaerobe facultative and showed a lower ability of bacterial infiltration, in respect to the aerobe _P. aeruginosa_[2; 31]. Although there are some little differences among the percentage of mean total infiltration, no significant differences have been found among the three types of connections. The percentage of total bacterial infiltration was comprised between the 20 and the 50%, and the results are totally in line with previous work of [PERSON] et al. [4] and in the study of [PERSON] et al. [32], in which 20% of bacterial infiltration in the Cone-Morse group was determined. In our previous studies, in which the same methodology was applied, none or little bacterial leakage was observed in Cone-Morse connections compared to other connections [4; 5; 20; 28; 29; 32]. These results have been supported by the literature [14; 15; 20; 21; 33; 34]. [PERSON] et al.