Ecological Characteristics of the Soft Plaque Microbiome: Influence of External Factors and Biodiversity Indexes

Orthodontic appliances placed on the outer surface of the tooth row cause an increase in microbial biomass. To control the growth of microbial biomass, it is recommended to use hygienic rinses for the oral cavity. Analyzing alpha diversity in microbial ecology is one of the first steps in assessing differences in the microbial community composition under the influence of various factors. Objective. To apply diversity indices to analyze changes in the microbial composition of soft dental plaque under the influence of an oral hygiene rinse in patients with braces. Methods. The effect of an alcohol-free rinse was studied in vivo. Controls were washes obtained from patients undergoing orthodontic treatment before the rinse use; subsequent samples were collected on days 30, 60, and 90. Microorganisms were identified based on cultural and morphological characteristics, as well as biochemical features using tests. Changes in the soft dental plaque composition were studied using quantitative counts (lg CFU/mL) and alpha diversity indices (Shannon, Simpson, Chao_1). Results. The analysis of the frequency of microorganism associations in the samples demonstrated the presence of Lactobacillus spp., Streptococcus spp. α, Corynebacterium spp., Propionibacterium spp., and Streptococcus spp. β (62.5–100 %). Streptococcus spp. γ was found with a frequency of 50 %, while Neisseria spp. was slightly less frequent (25 %), and Fusobacteria spp. and Actinomyces spp. were only 12.5 %. The proportions of pathogenic microorganisms Staphylococcus spp. and Peptostreptococcus spp. were 37.5 % either. Neisseria spp. and Staphylococcus aureus were 25 % either, and a small proportion of E. coli strains (12.5 %) were also detected. Additionally, fungi of the genus Candida were found in 62.5 % of the samples. After using the mouthwash, bacteria such as E. coli, Staphylococcus aureus, Neisseria spp., and Corynebacterium spp. significantly had reduced their presence or disappeared completely by the 60th and 90th days. The values of H indicate moderate heterogeneity of the microbiota in the structure of microbiocenoses before the use of rinses (1.77±0.24). The Simpson index showed a tendency to change in the composition of dominant groups (0.706±0.08 to 0.808±0.05). The value of the Chao_1 index indicates the richness of microcenoses in the studied samples: its average value ranged from 4.91±1.59 to 6.99±2.12. Conclusions. The composition of the microbiocenosis of soft plaque is represented by bacteria belonging to four phylum Firmicutes, namely Proteobacteria, Actinobacteria, Fusobacteria and fungi of the genus Candida. The alpha biodiversity indices and quantitative indicator demonstrated a tendency toward a decrease in microbial richness on the 30th day, with a significant decrease observed on the 60th day.