Among the species that increased only in the OC vs. PAI-3 comparison, there are: A. geminatus, which is an obligate anaerobe species and D. pneumaosintes, P. baroniae, F. fastidiosum, S. exigua and O. uli, that are all anaerobic, microaerophilic, or facultatively anaerobic species commonly found in the context of periodontitis and, specifically, in periapical root canal infection [29,30,31]. This evidence concerns the gene SERPINA5 and periodontitis.