## 4 Discussion
The greatest prevalence of periodontal pathogens found in patients with periodontitis were _P. gingivalis_, _P. intermedia_, and _E. nodatum. P. gingivalis_ and _P. intermedia_ are more specific for smokers suffering from periodontal disease, regardless of whether the tobacco is heated or burned. Studies have confirmed the positive correlation between red complex bacteria and the severity of periodontitis. The presence of red complex bacteria in periodontal pockets clinically demonstrated more destruction of periodontal tissues in severe forms of periodontal disease, when compared to moderate or mild forms [25; 48; 49; 50; 51; 52]. A surprising result observed in the present investigation was the highest abundance of _A. actinomycemcomitants_ in the non-smoker group without periodontal disease, as this information is not supported by the vast majority of published studies focusing on its prevalence [37]. Additionally, _A. actinomycemcomitants_ was the most deficient in IQOS users, regardless of whether they had or did not have periodontal disease. These data may be explained by the IQOS aerosol having some kind of inhibitory effect on the growth and reproduction of _A. actinomycemcomitants_; however, future larger-scale investigations with bigger samples can provide more exact insights regarding the accuracy of our findings. Periodontitis, as a multifactorial and complex disease, cannot be manifested without its primary and basic component: micro-organisms. This is an irreplaceable ingredient without which the inflammatory disease cannot occur. The oral cavity microbiome is a dynamic and diverse orchestra which consists of small, interconnected fractions. These polymicrobial fractions need to interact and work together to resist the host immune system, determinate and create an environment favorable to their growth, and provoke the destruction of periodontal tissues via inflammation [3; 49; 53; 54]. The fact that perio-pathogenic bacteria are present in gingival sulci or pockets does not mean that illness will occur [10; 49]. Full-mouth extraction therapy can not eliminate all periodontal pathogenic bacteria which has already been proved [55]. Another interesting research study on this topic actually found significant quantities of red complex periodontal pathogenic bacteria on complete denture patients [56]. Microbial shifts, host inflammatory responses, and environmental factors such as smoking and genetics are all etiological factors that are involved in the development of periodontitis [57; 58; 59]. This information can explain our finding regarding _A. actinomycemcomitants_, which was abundant in non-smokers without periodontal disease. _A. actinomycemcomitants_ may need some other bacteria, component, host or environmental factor, or some other piece of the puzzle to promote its pathogenicity, occurrence, and manifestation of full virulence potential. Furthermore, as _A. actinomycemcomitants_ serotype B and JP2 clones have been recorded in past studies, it may be possible that only a small subset of clone types of _A. actinomycemcomitants_, and not all types, are responsible for the localized aggressive destructive appearance of _A. actinomycemcomitants_; however, this speculation is beyond the scope of our study [10]. We must note that, even though all regarding the quantities of subgingival microbiomes were not related to the study groups at a significant level, it appears that smoking favors the colonization of almost all perio-pathogenic bacteria in smokers, when compared to non-smokers. Tobacco products of all kinds are harmful--some more than others--and their detrimental effect on the subgingival microbiome was confirmed in this study. IQOS aerosol exhibited an increasing effect on the quantity and prevalence of _P. gingivalis_, _F. nucleatum_, and _P. intermedia_, three of the most important pathogens; thus, we cannot consider it to be safe and benign.