title: Expression levels of matrix metalloproteinase-9 and gram-negative bacteria in symptomatic and asymptomatic periapical lesions.
abstract: BACKGROUND
  The aim of this study was to test the hypothesis that the expression of matrix metalloproteinase (MMP)-9 is significantly elevated in patients with symptomatic apical periodontitis and to correlate this with the detected amount of gram-negative bacteria.
  
  
  METHODS
  Twenty-six patients with periapical lesions involving at least 2 teeth were included in this study. The patients were divided into 2 groups: the symptomatic (SYM) group included 13 patients expressing pain with periapical lesions, and the asymptomatic (ASYM) group included 13 patients expressing no pain. Root canal treatment was performed followed by endodontic surgery and periapical lesion collection. Periapical lesions were serially cut into 4-μ sections. Some sections were processed for histologic examination using hematoxylin-eosin stain. Other sections were processed for immunohistochemical examination. For MMP-9, the area fraction of the positive cells was measured, and the percentage of the MMP-9-immunopositive area to the total area of the microscopic field was calculated. For gram-negative stain cells, the number of cells showing the pink-red color was counted per microscopic field. The Student's t test was used to compare the SYM and ASYM groups. The Pearson correlation coefficient was used to determine a significant correlation between the number of cells and the MMP-9 level. The significance level was set at P ≤ .05.
  
  
  RESULTS
  The SYM group showed a statistically significantly higher mean number of gram-negative cells (P = .001) and MMP-9 area percent (P < .001) than the ASYM group. There was a statistically significant positive (r = .927) correlation between the number of gram-negative cells and the MMP-9 area percent (P< .001).
  
  
  CONCLUSIONS
  There is good evidence to suspect a significant role of gram-negative bacteria and MMP-9 in symptomatic periapical lesions.
authors.affiliation: Endodontic Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
authors.forename: Geraldine M
authors.initials: GM
authors.lastname: Ahmed
authors.forename: Alaa A
authors.initials: AA
authors.lastname: El-Baz
authors.forename: Ahmed Abdel Rahman
authors.initials: AA
authors.lastname: Hashem
authors.forename: Abeer K
authors.initials: AK
authors.lastname: Shalaan
mesh_terms: D000293:Adolescent; D000328:Adult; D058345:Asymptomatic Infections; D015169:Colony Count, Microbial; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D006801:Humans; D020784:Matrix Metalloproteinase 8 / Q000378:metabolism*; D010485:Periapical Periodontitis / Q000201:enzymology* / Q000382:microbiology* / Q000601:surgery; D012390:Root Canal Therapy; D018709:Statistics, Nonparametric; D055815:Young Adult
chemical_list: D020784:Matrix Metalloproteinase 8