ALP assay and alizarin red staining of DPSCs in the mineralization-inducing media. (A) ALP concentrations in DPSCs at different passages. DPSC-P9 group presented a higher ALP level (P < 0.001) than DPSC-P1 group after 3 d or 7 d induction. (B) Alizarin red staining demonstrated that DPSC-P9 group generated more calcification nodules than DPSC-P1 group after 14 d induction in the mineralization-inducing media. (C) Calcium concentrations in DPSC-P9 group was significantly elevated (P < 0.001), as compared with DPSC-P1 group. Values are mean ± s.d., n = 9 (**P < 0.001, Student's t-test).