The effects of various mixing solutions on the biocompatibility of mineral trioxide aggregate. 
To evaluate the effects of various mixing solutions on the biocompatibility of mineral trioxide aggregate (MTA).  Human alveolar osteoblasts (hOAs) were incubated with eluates of 24 h-set cement discs of MTA mixed with sterile H2 O, 3% sodium hypochlorite (NaOCl), 4% articaine (Ultracain(®) D-S), 0.9% NaCl, Ringer's solution or citrated blood, respectively.  The cell proliferation in the presence of eluates was assessed by real-time cell analysis, and the expression of genes associated with proliferation (histone H3, HistH3), inflammation (interleukin-6, IL-6, matrix metalloproteinases 1 and 3, MMP1, MMP3) or apoptosis (caspase 3, Casp3) was analysed by qPCR after 24 and 72 h. The ultrastructure of cells grown on cement discs was visualized by scanning electron microscopy (SEM), whilst actin cytoskeleton was monitored by fluorescence staining in the presence of eluates after 7 and 14 days.  A repeated-measure analysis was performed, and P-values were adjusted by Tukey.  Whilst articaine-MTA sustained hOA proliferation patterns similar to H2 O-MTA, NaOCl-MTA reduced hOA proliferation and significantly increased the expression of MMP1 and MMP3.  The addition of H2 O and articaine modulated the gene expression of Casp3 or Hist3H3.  The use of NaCl, Ringer and blood induced mRNA levels comparable to matched controls.  With the exception of NaOCl-MTA, SEM and FM revealed regular hOA morphology for all mixing solutions.  NaOCl was highly cytotoxic for hOAs whilst all other mixing solutions can be considered as convenient biocompatible mixing solutions as alternatives to H2 O for clinical use.