title: A meta-analysis of MMP-9 promoter -1562 C/T polymorphism on susceptibility of chronic periodontitis.
abstract: BACKGROUND
  Although many studies have focused on the association of the MMP-9 promoter -1562 C/T polymorphism with the susceptibility and/or severity of chronic periodontitis (CP), results have been inconsistent. Therefore, a meta-analysis of all eligible studies was performed to derive a more precise estimation of the association between this polymorphism and CP risk.
  
  
  METHODS
  All relevant studies were identified through a database search in PubMed, Medline, and Web of Science. All the full-text studies with appropriate analytical design, published in English, which evaluated the association of MMP-9 promoter -1562C/T polymorphism with CP risk using validated genotyping methods, and with non-duplicated data were selected for this study. A fixed-effect model was used to calculate pooled ORs in the absence of heterogeneity across included trials (P > 0.1 and I(2) < 50 %), otherwise the random-effect model was applied.
  
  
  RESULTS
  In an overall meta-analysis, pooled ORs revealed that T variant in the MMP-9 promoter -1562 C/T polymorphism was associated with a significantly decreased risk for CP under all comparison models. In subgroup analyses by ethnicity, pooled ORs showed that a significant association of the MMP-9 promoter -1562 C/T polymorphism with CP risk was only detected in Caucasians and Asians but not in mixed population. In the subgroup analysis by severity of CP, pooled ORs indicated that T allele of the MMP-9 promoter -1562 C/T polymorphism was associated with decreased susceptibility to severe CP while there was no significant association between this polymorphism and moderate CP.
  
  
  CONCLUSIONS
  Our meta-analysis showed that T allele in the MMP-9 promoter -1562 C/T polymorphism might be a protective factor for CP, especially in Caucasians and Asians. Moreover, there was a significant association of the MMP-9 promoter -1562 C/T polymorphism with decreased susceptibility to severe CP, while the allelic and/or genotype distributions of this polymorphism were not associated with moderate CP.
authors.affiliation: College of Stomatology, Chongqing Medical University, Chongqing, 400016 China.|Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China.|Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China.
authors.forename: Deepal Haresh
authors.initials: DH
authors.lastname: Ajmera
authors.affiliation: College of Stomatology, Chongqing Medical University, Chongqing, 400016 China.|Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China.|Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China.|Department of Oral and Maxillofacial Surgery, College of Stomatology, Chongqing Medical University, Chongqing, China.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Singh
authors.affiliation: Department of Forensic Medicine, Faculty of Basic Medical Sciences, Chongqing Medical University, Chongqing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: College of Stomatology, Chongqing Medical University, Chongqing, 400016 China.|Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China.|Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China.|Department of Oral and Maxillofacial Surgery, College of Stomatology, Chongqing Medical University, Chongqing, China.
authors.forename: Wenyang
authors.initials: W
authors.lastname: Li
authors.affiliation: College of Stomatology, Chongqing Medical University, Chongqing, 400016 China.|Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China.|Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China.
authors.forename: Jinlin
authors.initials: J
authors.lastname: Song
keywords: Chronic periodontitis; Matrix metalloproteinase-9; Meta-analysis; Polymorphism