## 4 Discussion
The incidence of _Leptotrichia_, _Prevotella_, and _Fusobacterium_ was relatively high. The second group included the right MIM- molars with relatively high _Streptococcus_ and _Veillonella_. Sample 36-2 showed a relatively large number of _Fusobacterium_. _Fusobacterium_ is an absolute anaerobic gram-negative bacterium with a long filament, which is isolated from periodontal tissue and can aggregate with other oral bacteria [24]. It is one of the signs of acute dentalveolar infection [15]. Among the endo group, samples 16-4, 16-5, and 36-5 showed four phyla and 36-4 showed two phyla. _Saccharibacteria_TM_ and _Proteobacteria_ was not present as compared to the Perio group. At the genus level, _Parcimonas_, _Peptostreptococcus, _Atopobium_, and _Dialister_ were present in all the endo group samples. The anaerobic gram-positive cocci _Parimonas_ and _Peptostreptococcus_ have been identified from caries dentin, infected pulp, and complex infections such as dental root can, progressive periodontitis, and dental abscesses [15,25]. _Atopobium_ was originally identified as an anaerobic lactic acid bacillus in a periodontal pocket. _Dialister_ is a gram-negative bacterium, which is an absolute anaerobic and found in root canal infections and periodontal infections [25]. In addition, _Shuttleworthia_, _Bulleidia, Mogibacterium_, and _Olsenella_, identified at 1% frequency, are present in the root canals in endodontic-periodontal lesion [25]. Regarding species, the endo group showed significant numbers of gram-positive anaerobic cocci species, such as _Peptostreptococcus stomatitis_ and _Paryimonas mica_. According to the new classification of periodontal disease in 2018, general periodontitis is different from MIM complications because they usually start after middle-age [26]. In addition, early-onset periodontitis (EOP), localized juvenile periodontitis (LJP), or aggressive periodontitis (AP), categorized as periodontitis in the 2018 classification, were also different [27]. Although the location in the molar and incisor, and the sudden periodontal abscess were similar to MIM complications, MIM complications develop before puberty while EOP, LJP, and AP develop during puberty. AP was associated with _Aggregatibacter actinomyces_, but it was not identified in the MIM-complicated molar. In the 2018 classification, \"Other conditions affecting the periodontium\" included periodontal abscess, endodontic-periodantal lesions, and localized tooth-related factors [28]. In the localized tooth-related factors, tooth anatomy such as cervical enamel projections, enamel pearls, and developmental grooves could enhance plaque retention [29; 30]. Due to the inability to keep these areas clean, it was always accompanied by a poor prognosis despite adequate treatment. According to previous studies, the root malformation of MIM resembled cervical enamel projections, enamel pearls, and developmental grooves and cementum deformation were also confirmed [2]. Biofilm was present in the cervical lower part of the crown in the study by [PERSON] et al. [31]. Periodontitis in MIM seemed to begin as localized tooth-related periodontitis and on further progression, it was assumed to be a periodontal abscess with a severe anatomic alteration. Pulp necrosis occurs in all teeth affected by MIM regardless of the severity of the periodontitis. Pulp necrosis of MIM teeth could spontaneously occur due to the lack of nutrients and oxygen supply [32]. The anatomical characteristics of MIM seem to cause pulp necrosis and localized tooth-related periodontitis independently, and when combined, an endo-perio lesion might form. If a purulent bacterial infection was added to this, a periodontal abscess could occur [32]. There are two case reports of successful endodontic treatment of MIM teeth. [PERSON] and [PERSON] [9] successfully performed endodontic treatment of a MIM mandibular left permanent first molar of a 13-year-old boy and [PERSON] et al. [10] treated MIM-suspected maxillary central incisors endodontically in a 12-year-old boy.