MMP9 and periodontitis: In the subgroup analyses by the disease type, there was a significant association between MMP-9 -1562C>T polymorphism and periodontitis risk under the homozygote model (TT vs. CC: OR=0.375, 95% C=0.146–0.964, P=0.042) and the recessive model (TT vs. TC+CC: OR=0.473, 95% C=0.235–0.954, P=0.036) in the CP group.