MMP9 and alkaline phosphatase measurement: Low-to-moderate positive correlation was found between PAI-AP severity and GCF sclerostin, GCF RANKL, GCF MMP-9, and PGE2 levels (rs = 0.497, 95% CI: 0.3471 to 0.6216, p < 0.0001; rs = 0.231, 95% CI: 0.05264 to 0.3954, p = 0.0095; rs = 0.297, 95% CI: 0.1235 to 0.4539, p = 0.0008; and rs = 0.335, 95% CI: 0.1640 to 0.4861, p < 0.0001; respectively) (Fig. 3).