Fig 1.
Dentition stage of the subjects, sampling tooth positions and corresponding groups.
i) Dentition stage: mixed dentition stage with 10–12 fully or partially erupted permanent teeth (4 first permanent molars, 6–8 permanent incisors). ii) Sampling tooth positions and their corresponding groups: first permanent molars, PM; deciduous molars, DM; deciduous canines and incisors, DC; and permanent incisors, PI.
Table 1.
Demographic characteristics of the subjects and sample size.
Fig 2.
Microbial community variation within groups using weighted UniFrac distance.
(A) The weighted UniFrac distance values of PM, DM, DC, and PI. PM and PI sites tended to host diverse bacterial communities, whereas DM and DC harbored similar microbial communities. All data are presented as medians and 10th, 25th, 75th, and 90th percentiles. **P < 0.01 by two-tailed t-test. (B) A principal coordinate analysis (PCoA) based on the weighted UniFrac distance values.
Fig 3.
Bacterial composition of supragingival plaque samples.
(A). Relative abundances of the resident bacterial phyla at various sampling sites. (B, C). Relative bacterial abundance at the genus level. Genera with a mean relative abundance value >0.1% are shown. Bars indicate mean relative abundances with standard deviations. The significance of differences among groups was determined using the Kruskal—Wallis test. *P < 0.05.
Fig 4.
Relative abundances of the main bacterial phyla identified in dentition sites.
A–E. Relative abundances of Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria and Actinobacteria in the four groups. The four groups are presented in distal—mesial order according to location in the dentition. All data are presented as means with standard deviations. *P < 0.05, **P < 0.01 by two-tailed t-test.
Fig 5.
Microbial communities in permanent teeth (PT) and deciduous teeth (DT).
(A) A principal coordinate analysis (PCoA) based on weighted UniFrac distances suggested similar relationships among the 76 samples. Samples collected from the same individuals are shown as connected by arrows. The DT→PT pairs consisted of DM→PM and DC→PI pairs since DM and PM, DC and PI had similar morphological characteristics (four free PI dots resulted from four missing DC samples). Most marked arrows displayed a trend in the negative to positive direction of PC3, suggesting the possibility of an analogical microbial transformation upon replacement of teeth in the mixed dentition. (B) Venn diagram of the shared and unique OTUs between PT and DT. Of the total OTUs, 25.2% and 20.9% were unique to PT and DT, respectively. (C) The microbial composition variation was compared using the LEfSe online tool. The difference in the microbial community at the genus level was due mainly to Actinomyces and Treponema.
Table 2.
Taxa common among the PM, DM, DC and PI sites in mixed dentition.
Fig 6.
“Core microbiome” in the mixed dentition.
The dots represent genera that belong to the “core microbiome”. The dot size indicates the mean relative abundance of the corresponding genus in all samples. Colors indicate the different phyla. Lines link two genera having coefficient values >0.4. Line thickness indicates the coefficient value. Red and blue lines indicate positive and negative correlationships, respectively. From a macroscopic perspective, this core microbiome could be divided into a relatively simple (a, c) and a relatively complex interaction component (containing the Lautropia—Haemophilus—Abiotrophia and Prevotella—Fusobacterium—Leptotrichia—Campylobacter groups, b).