# _Stretococcus mutans_ Associated with Endo-Periodontal Lesions in Intact Teeh
## 4 Discussion
As observed in this research, all teeth selected in the study were negative for caries, pulpal exposures, root damage, and old restorations that could justify pulpal necrosis. It is suggested that a severe periodontal lesion can secondarily involve endodontic tissues. In this study, the presence of _S. mutans_ strains has been investigated by using traditional culture-based methods and biomolecular methods. In the past, the study of oral microbiome was limited to the sole use of conventional culture-dependent techniques, but in some cases the abundant oral microflora could not be cultured for different reasons. The discovery of new genomic technologies, including NGS and bioinformatics, has finally revealed the complexities of the oral microbiome, thus providing a powerful means of studying the whole microbial communities [2]. In addition, next-generation techniques could help to understand the different composition of the oral microbiome in health subjects and in injured patients, which will give further information to explore the functional and metabolic alterations associated with the pathological cases and to identify molecular signatures for antibiotics and drug development, as well as to specifically targeting the therapies [1]. In this study, the use of NGS targeting the highly conserved specie-specific _gtf_B gene target and sequence technologies have been chosen for their sensitivity and specificity compared to traditional culture-based approaches, which still remains fundamental to confirm the presence of the alive bacteria. In particular, although a few growth media are available for selective isolation of the cariogenic Streptococcus, it is still unclear as to which is the most sensile and efficacious [16]. Moreover, each species requires a specific protocol, and this greatly lengthens the time required for diagnosis. Therefore, the use of targeting-specific PCR, when applicable, could be useful to precisely detect the microbial species, especially for detection of specific bacterial genes, in a shorter time period. In this case, we were able to isolate, with a culture-based method, the _S. mutans_ strains only in 50% of samples in which the _S. mutans_ DNA was observed, therefore the two different methods must be considered as complementary tests and when possible, they have to be both carried out in order to obtain a result as specific/sensitive as possible in a shorter possible time. Moreover, _S. mutans_ can migrate from periodontal pocket into endodontic system without clinically coronal leakages such as caries, traumatic tooth fractures, or old restorations. It is well-known that _S. mutans cnm_-positive strains have the ability to invade the endothelial cells with a subsequent periodontal vascular damage, and the possibility to migrate in bloodstream with potential life-threatening pathologies like infective endocarditis or disseminating infections, especially in patients with pre-existing cardiovascular conditions or compromised immune system [11; 17]. The expression of _cnm_ gene in _S. mutans_ enhances its local virulence with capability of epithelial and endothelial invasion, and this pathogen has to be considered as a potential periodonto-pathogen in severe or refractory forms of periodontal diseases. Of note, _S. mutans cnm_-positive isolate found on RS samples of patient n = 4 was found to express a different genetic pattern compared to the one detected in the endodontic micro-environment. Interestingly, only in 1 sample was the positivity to the _cnm_ gene contemporarily detected in RC and RS samples of the same patient. We hypothesize that the acquired properties obtained from this gene detection have less utility in necrotic endodontic tissues with lack of pulpal bloodstream. Instead, the function of the \(cbm\) gene is not yet well-defined, but it is thought that it also guarantees adhesiveness, invasiveness in endothelial and epithelial cells, and virulence to \(S\). \(mutans\) strains. The presence of \(S\).