MMP9 and periodontitis: In the subgroup analyses by ethnicity, there was a significant association between MMP-9 -1562C>T polymorphism and periodontitis risk under all genetic models (allele model: T vs. C, OR=0.723, 95% C=0.572–0.914, P=0.007; heterozygote model: TC vs. CC, OR=0.753, 95% CI=0.568–1.000, P=0.050; homozygote model: TT vs. CC, OR=0.347, 95% CI 0.133–0.909, P=0.031; dominant model: TT+TC vs. CC, OR=0.709, 95% CI=0.538–0.936, P=0.015; and recessive model: TT vs. TC+CC, OR=0.378, 95% CI=0.145–0.983, P=0.046) in the Caucasians, but not in Asian and Latinos populations.