## 4 Discussion
### Multi-Bracket-PMTC-Microbiota  
The oral microbiota is significantly more variable in individuals with high caries activity than in those with healthy oral environments [31]. The diversity of oral bacteria was significantly higher in individuals with a healthy oral environment, without caries or periodontal tissue disease, than in those with high caries activity [32]. This result indicates that an increased diversity of the oral microbiota is a critical factor for maintaining a healthy oral environment. In this study, no significant difference was observed in the change in the Shannon index with the continuation of PMTC, although it showed an increasing trend over time. The Chao1 index increased over time and showed statistical significance. These results suggest that the continuation of PMTC among multi-bracket wearers indicates an improving trend in the oral environment. Plaque accumulation increases the risk of caries and periodontitis morbidity [33]. Wearing multi-bracket appliances allows for large amounts of plaque accumulation [34]. Furthermore, multi-bracket appliance wearers have an increased microbial load compared to individuals who do not wear any [35]. In this study, PCR scores decreased over time with continuous PMTC; thus, it indicates that continuous PMTC prevents dental caries and periodontal disease in multi-bracket appliances, and is an essential means of maintaining the oral environment. Enhancing patient motivational education regarding periodontal disease management is fundamental to the prevention of periodontal disease [36]. Ensuring PMTC and providing careful oral cleaning instructions based on an individual's oral cleaning status will significantly reduce this risk among multi-bracket appliance wearers. Based on an investigation of the effectiveness of person-centered oral hygiene behavioral interventions in general dentistry and the reinforcement of instruction in behavior change [37], this study \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Mean \(\pm\) SD**} & \multicolumn{2}{c}{**Friedman Test**} & \multicolumn{2}{c}{**Wilcoxon Test**} \\ \hline T0 & T1 & T2 & T0–T1–T2 & T0–T1 & T1–T2 & T0–T2 & T0–T2 \\ \hline PCR Score & 58.6 \(\pm\) 16.7 & 38.0 \(\pm\) 14.9 & 29.5 \(\pm\) 16.9 & 1.88 \(\times\) 10\({}^{-8}\) * & 2.84 \(\times\) 10\({}^{-5}\) * & 5.83 \(\times\) 10\({}^{-3}\) * & 1.19 \(\times\) 10\({}^{-6}\) * \\ \hline \hline \end{tabular}  
* Significant (\(p\) < 0.01.).  
\end{table} 
Table 5: Average of plaque control record (PCR) scores for each session and statistical result. suggests the need to establish person-centered oral hygiene education programs targeting behavioral interventions in orthodontics. PCR is a strict assessment of oral hygiene status. [PERSON] et al. [38] showed that OHI (oral health education and oral hygiene instruction) significantly improved oral hygiene without affecting bacterial levels. This result is consistent with the lack of changes in the oral bacterial microbiota in the present study. A chemical approach is necessary to reduce bacterial levels [39]. A study on plaque index and oral hygiene instructions [40] showed significant short-term improvement in oral hygiene. However, 6 months after the education, oral hygiene levels declined. This suggests that continued long-term oral hygiene instruction during treatment may influence risk reduction and avoidance in multi-bracket appliance wearers. In this study, no significant difference in the oral microbiota was observed with continuous PMTC at any stage from the phylum to the species level. Bacteroides were found in the oral cavity and intestines at the phylum level. Oral Bacteroidetes include periodontalpost pathogenic bacteria, such as _P. gingivalis_ and _P. intermedia_. Additionally, TM7 is associated with periodontitis, increases with age, and has been implicated in periodontitis [41, 42]. Previous studies have shown an increasing trend in Bacteroidetes before and after wearing multi-bracket appliances [8]. A significant increase was also observed in TM7 [8].