Figure 3.

Shannon index difference between groups. The Shannon indexes of groups H, P and U were 5.41, 5.38 and 5.22, respectively, and the difference between groups was statistically significant (^*P<0.05). This indicated that the species diversity of the periodontal microecological environment in group U was decreased, suggesting that periodontal tissue after treatment with unprepared porcelain veneers may be in a certain pathological stage due to the pathogen aggregation and formation of a core pathogenic complex. H, healthy control; P, prepared porcelain veneers; U, unprepared porcelain veneers.