Figure 4. Effects of root-end filling material on alkaline phosphatase activity. Alkaline phosphatase activity was measured colorimetrically for PDL fibroblasts and gingival fibroblasts (GF) grown in the presence of plastic (solid diamonds), MTA (solid squares), HICR (solid triangles), and bone particles (circles) for from 1 to 17 days in culture. Enzyme activity was compared for PDL fibroblasts (A,C) and gingival fibroblasts (B,D) cultured in the presence of fresh (C and D) and washed (A and B) root-end filling materials. Note that the PDL fibroblasts expressed approximately twice the alkaline phosphatase activity of gingival fibroblasts. Each point represents the mean of 4 samples. Error bars represent standard deviation from the mean. ANOVA analysis was applied to all the values, and statistical significance was determined at p < 0.01. Data points represent a typical experiment that was repeated in triplicate.