Microbial composition of dental plaque microflora on first molars with orthodontic bands and brackets, and the acidogenic potential of these bacteria

Purpose: In order to elucidate the characteristics of orthodontic appliance-associated dental plaque, this study aimed to profile the microflora and to estimate the acidogenic potential of supragingival plaque on first molars with orthodontic bands or brackets or without appliances. Material and methods: Supragingival plaque samples from the surface of upper and lower first molars with orthodontic bands or brackets or without appliances in 6 subjects (age, 11-30 years) were cultured anaerobically on blood agar plates. Isolated bacteria were identified by 16S rRNA sequencing. The acidogenicity of isolated bacteria was examined using fastidious anaerobe agar plates containing bromocresol. Results: Bacterial growth (log CFU/mg) was 6.6±6.5, 6.9±7.1, and 7.4±7.6 in samples obtained from molars with bands, brackets, and without appliances, respectively. Actinomyces (43.5 and 40.0%) and Streptococcus (23.5 and 34.7%) were the predominant species present on molars with orthodontic brackets and without appliances, respectively. In contrast, the proportion of Streptococcus (44.4%) was higher than that of Actinomyces (17.6%) on molars with orthodontic bands (P<0.01). The proportions of acidogenic bacteria in plaque samples from molars with bands, brackets, and without appliances were 74.5%, 71.3%, and 81.6%, respectively, although these differences were not statistically significant. Discussion and conclusion: These results indicate that there are differences in the microbial composition and acidogenic potential of supragingival plaque from first molars with bands, brackets, or without appliances, and suggest that supragingival plaque on teeth with brackets carries predominantly periodontitis-associated bacteria but less caries-associated bacteria.