Figure 4.

Relative abundance of species in oral microbial community of each group at the phylum level. This chart revealed the first five dominant phyla with high abundance in each group at the phylum level, which were Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria and Actinobacteria. The abundance of dominant bacteria in each group was basically the same, but the difference of Proteobacteria in these three groups was statistically significant (^*P<0.01). The proportion of Proteobacteria in gingival crevicular fluid of group U was higher than that of group P and group H. H, healthy control; P, prepared porcelain veneers; U, unprepared porcelain veneers.