公益財団法人 セコム科学技術振興財団
研究成果報告書研究課題名

ヒト・デンタルバイオフィルムの次世代シーケンス網羅的解析に基づく制御法の開発
Development of control methods of human dental biofilms
based on comprehensive analyses using next-generation sequencing

研究期間
平成 29 年 10 月～令和 4 年 3 月

報告年月
令和 4 年 4 月
研究代表者
大阪大学大学歯学研究科 教授
林 美加子
Osaka University Graduate School of Dentistry, Professor
Mikako HAYASHI

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Abstract
We investigated the effect of sleep on the microbiome of oral biofilm (buccal mucosa, palate,tongue, gingival mucosa, tooth surface, saliva). Prevotella had higher relative abundance on awaking
than before sleep in all location of the oral cavity, whereas Streptococcus tended to be higher before
sleep than awaking. Furthermore, we investigated the effect of sleep on the dental biofilm using anin situ biofilm model. No significant changes in the numbers of biofilm –forming bacteria were causedby sleep. However, the relative abundance of Fusobacterium and Prevotella were significantly higher
after awaking. Confocal laser scanning microscopy showed that the volume of exopolysaccharide wassignificantly larger before sleep than awaking. We clarified that although no quantitative changes
due to sleep were observed, qualitative changes such as the bacterial flora and three-dimensional
structure of the biofilm occurred.
The microbiota related to root caries was investigated. The relative abundance ofActinomyces and Streptococcus were higher in the caries-affected dentin compared to the healthy root
surfaces. In addition, these bacteria have a higher relative abundance in initial caries than inadvanced caries and deeper site in the cavities. We showed that the biofilm microbiota was different
between the healthy and caries-affected sites, and that the microbiota was different depending on theprogress of root surface caries.
We have been investigated the healthy human core microbiome. For this purpose, we tried
to elucidate healthy core microbiome of Japanese older adults at the age of 90 and compared the coremicrobiome of the children living isolated area in Myanmar. We also tired selective tooth surface
disinfection by antimicrobials chlorhexidine for the patients with fixed orthodontic appliance.
The core microbiome of the healthy Japanese older adults at the age of 90 was abundant in
Firmicutes. Many species that can use for probiotics were abundant. However, some species that are
the agents of pneumonia were abundant. This tendency was similar to the result of our previous
report that investigated the core microbiome of the four Japanese centenarians. In contrast,
Proteobacteria was abundant in the core microbiome of the children living in isolated area in
Myanmar. These results indicated that core microbiome was affected by the living area or lifestyles.
In the study of selective tooth surface disinfection, we analyzed the microbiome of thepatients with orthodontic treatment by fixed orthodontic appliance. The study design was open
labeled randomized controlled trial. The patients were randomly allocated to conventional preventivetreatment with fluoride application groups and additional tooth surface disinfection groups. The oral
microbiome was analyzed twice at the baseline and after 6 months of preventive treatment. Inaddition, tooth white spot lesions were also investigated. Salivary levels of mutans streptococci weresignificantly reduced in tooth surface disinfection group. In addition, some species that have beensuggested to be the pathogens for pneumonia were reduced in tooth surface disinfection group.
However, at the phylum levels, drastic changes of the microbiome was not observed. Some species had
significantly strong correlation with area and volume of white spot lesions. These results indicatedthat even by using antimicrobials, drastic changes of microbiome compositions were not induced.
Therefore, microbiome may be stable in the short span of human life.
In summary, there may be healthy core microbiome that consisted by beneficial species forhuman body. However, human oral core microbiome included some pathogenic species. . And
composition of oral microbiome was affected by the living area and lifestyles. It is stable during shortspan of human life.

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