Meanwhile, the results of Pearson correlation test showed negative correlation between the miR-1226 expression levels and the probing pocket depth (r = -0.806, P < 0.001), attachment loss (r = -0.764, P < 0.001), and MMP-8 concentration (r = -0.654, P < 0.001) in patients with periodontitis (Fig. 2). Here, MMP8 is linked to periodontitis.