*2.9. Statistical Analysis*

Data were analyzed using the SPSS software v.18.0 (International Business Machines Corp., Armonk, NY, USA). The Shapiro–Wilk (W test) was used for the normality test. Independent sample Student's *t* test was employed for the comparison of *S. mutans* counts in the biofilm of Core + *S. mutans* groups and *S. mutans* groups if normally distributed. One-way ANOVA was used for pH value, demineralization depth, mineral loss, and Keyes score analysis. Student–Newman–Keuls (SNK) test was used to identify the specific differences among groups. The significance level was set at 0.05.

#### **3. Results**
