MMP8 and periodontitis: The results of the χ2 test showed a close relationship between miR-1226 expression and the probing pocket depth (P = 0.002), attachment loss (P = 0.004), plaque index (P = 0.032), bleeding index (P = 0.012), and MMP-8 concentration (P = 0.001) in patients with periodontitis (Table 2).