Figure 4.

Effects of different hypoxic conditions on the alkaline phosphatase (ALP) activity of human periodontal ligament fibroblasts (HPLFs) at various time points: n=4, ^avs. 21% O₂ P<0.05, ^bvs. 2% O₂ P<0.05 (ANOVA and paired t-test). ALP activity shows a decrease at each time point as the degree of hypoxia increases. (A) At 12 h post-cultivation, no clear difference was observed between the hypoxic and control groups. (B) At 24 h post-cultivation, the ALP activity of HPLFs in the severe hypoxia (1% O₂) group was markedly restrained. (C and D) At 48 and 72 h post-cultivation, the ALP activities of HPLFs in the middle (2% O₂) and severe hypoxia groups were markedly restrained. The restraint was clearest in the severe hypoxia group.