Oral Microbiome Analysis and Caries Risk Classification Using the Caries Management by Risk Assessment System in Pre-Orthodontic Patients

<b>Background/Objectives</b>: This study aimed to classify pre-orthodontic patients using the Caries Management by Risk Assessment (CAMBRA) system and clarify their oral characteristics and microbiome. <b>Methods:</b> At the Department of Orthodontics, Hiroshima University Hospital, 68 patients were included in this study. Clinical parameters, such as plaque control record, DMF index, and number of white spot lesions (WSLs), were obtained. Medical interviews and oral examinations were conducted according to the CAMBRA system, and participants were classified into four risk groups (Low, Moderate, High, and Extreme). The supragingival plaques and stimulated saliva were collected. A saliva test was performed to measure the saliva secretion volume, pH, buffering capacity, and bacterial culture. Microbial DNA was extracted from the stimulated saliva and plaque samples, and 16S rRNA metagenomic analysis was performed. For statistical analysis, the Kruskal-Wallis test was used. <b>Results:</b> Participants were classified into four CAMBRA risk groups, with many classified as the High group. The number of DMF teeth and WSLs were the highest in the Extreme group, which tended to have the worst oral hygiene habits. The saliva test results revealed that the Extreme group had the worst saliva secretion volume, buffering capacity, and <i>Streptococcus mutans</i> score, with statistically significant differences. Bacterial 16S metagenomic sequencing revealed that the genus <i>Fusobacterium</i> had the highest relative abundance in the saliva samples of the Low group, whereas the genus <i>Actinomyces</i> had the highest relative abundance in the Extreme group. <b>Conclusions:</b> In this single-center, cross-sectional study, CAMBRA risk classification accurately reflected the oral condition of pre-orthodontic patients.