A meta-analysis of MMP-9 promoter −1562 C/T polymorphism on susceptibility of chronic periodontitis

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Table 1 Baseline characteristics of studies included for investigating the association of the MMP-9 promoter −1562 C/T polymorphism with periodontitis risk

References	Country	Ethnicity	Sample size (case/control)	Type of periodontitis	Matching criteria	Genotype method	HWE in controls
de Souza et al. (2005)	Brazil	Mixed	62/38	Moderate or severe CP	–	PCR–RFLP	0.623
Holla et al. (2006)	Czech	Caucasian	169/135	Moderate or severe CP	Age, gender, smoker ratios	PCR–RFLP	0.586
Keles et al. (2006)	Turkey	Caucasian	70/70	Severe CP	Age, gender	PCR–RFLP	0.816
Gurkan et al. (2008)	Turkey	Caucasian	87/107	Severe CP	Age, gender,smoker ratios	PCR–RFLP	0.017
Loo et al. (2011)	China	Asian	280/250	Severe CP	Age, gender	PCR–RFLP	0.001
Isaza-Guzman et al. (2011)	Colombia	Mixed	69/54	Slight to moderate to severe CP	Gender	PCR–RFLP	0.163
Li et al. (2012)	China	Asian	122/532	Severe CP	–	PCR–RFLP	0.001

MMP-9 matrix metalloproteinase-9, CP chronic periodontitis, GAgP generalized aggressive periodontitis, HWE Hardy–Weinberg equilibrium
Slight periodontitis: patients with teeth exhibiting <3 mm attachment loss; moderate periodontitis: patients with teeth exhibiting ≥3 and <7 mm attachment loss; severe periodontitis: patients with teeth exhibiting ≥7 mm attachment loss
A P value less than 0.05 of HWE was considered significant