Supragingival microbial profiles in caries-free and caries-active adolescents treated with fixed orthodontics

Dental caries occur primarily due to the formation of excessive dental plaque biofilm on teeth surfaces. This study aims to analyze the supragingival microbial profiles of permanent teeth in caries-free and caries-active adolescents with fixed orthodontic appliances and to identify bacterial biomarkers that may be indicative of caries activity in specific population. Twelve-year-old adolescents treated with fixed orthodontic appliances were selected as the study population, with 5 caries-free and 5 caries-active subjects. Supragingival plaque samples were collected from the first permanent molars for the 16S rRNA high-throughput sequencing analysis of the V3-V4 region. There was no significant difference in alpha diversity and beta diversity between the caries-free and caries-active groups. LEfSe analysis showed that differentially abundant genera such as Selenomonas_3 (S. haemophilus, S. abiotrophia and S. streptococcus), Oribacterium, Dialister, and Olsenella species in the caries-free group, and Streptococcus mutans (S. mutans), Neisseria, Haemophilus, Granulicatella, and Abiotrophia species in the caries-active group, could be identified as potential biomarkers (P < 0.05). Co-occurrence network analysis revealed significant synergistic relationships among bacteria, with Streptococcusspp. displaying the strongest associations with other genera. Increases in S. mutans and bacteria from the genera Neisseria, Haemophilus, Granulicatella, and Abiotrophia were strongly associated with the caries-active status of adolescents undergoing orthodontic treatment with fixed appliances. While increases in Selenomonas_3, Oribacterium, Dialister, and Olsenella were linked to caries-free status. These findings highlight the importance of managing the oral microbiome in adolescents with fixed orthodontic appliances, as certain bacterial species can serve as indicators of caries risk.