Abstract: PURPOSE: To detect the degradation of Ca(OH)₂ on lipopolysaccharide (LPS) extracted from Porphyromonas endodontalis (P.e) in vitro and estimate the influence of P.e LPS pretreated with Ca(OH)₂ on the proliferation of MC3T3-E1 cells. METHODS: The effect of Ca(OH)₂ on MC3T3-E1 cell proliferation was detected by methyl thiazolyl tetrazolium (MTT) assay. Then P.e LPS was treated with Ca(OH)₂ for 30 mins or 60 mins at 37℃ in vitro and the activity of P.e LPS was evaluated by Chromogenic End-point Tachypleus Amebocyte Lysate (CE TAL) test. Finally, MC3T3-E1 cells were exposed to P.e LPS pretreated with 15% Ca(OH)₂ for 1, 3 and 5 d, and the cell proliferation was measured using the MTT assay comparing with the P.e LPS control group. SPSS 13.0 software package was used for statistical analysis. RESULTS: Compared with the negative control, exposing cells to 5%, 10% and 15% Ca(OH)₂ had greatly promoted MC3T3-E1 cell proliferation. P.e LPS treated with 10% and 15% Ca(OH)₂ both presented the best results by CE TAL and significant difference compared with P.e LPS control group. When 10 μg/mL P.e LPS was pretreated with 15% Ca(OH)₂, no inhibition of MC3T3-E1 cell proliferation was noted. CONCLUSIONS: Ca(OH)₂ detoxifies P.e LPS in vitro, mitigates the impact of P.e LPS on MC3T3-E1 cell proliferation.

Key words: Calcium hydroxide, Lipopolysaccharide, Osteoblasts