MMP8 and periodontitis: Studies showed an overall effect favoring high MMP8 levels in periodontitis cases (unstimulated saliva collection: SMD: 1.61, 95% CI: 1.04–2.17, I2 = 92% and stimulated saliva collection: SMD: 0.69, 95% CI: 0.32–1.06, I2 = 57%).