title: Matrix metalloproteinase expression in teeth with apical periodontitis is differentially modulated by the modality of root canal treatment.
abstract: BACKGROUND
  The objective of this study was to investigate the expression of matrix metalloproteinases (MMPs) in apical periodontitis and during the periapical healing phase after root canal treatment.
  
  
  METHODS
  Apical periodontitis was induced in dog teeth, and root canal treatment was performed in a single visit or by using an additional calcium hydroxide root canal dressing. One hundred eighty days after treatment the presence of inflammation was examined, and tissues were stained to detect bacteria. Bacterial status was correlated to the degree of tissue organization, and to further investigate molecules involved in this process, tissues were stained for MMP-1, MMP-2, MMP-8, and MMP-9. Data were analyzed by using one-way analysis of variance followed by Tukey test or Kruskal-Wallis followed by Dunn test.
  
  
  RESULTS
  Teeth with apical periodontitis that had root canal therapy performed in a single visit presented an intense inflammatory cell infiltrate. Periapical tissue was extremely disorganized, and this was correlated with the presence of bacteria. Higher MMP expression was evident, similar to teeth with untreated apical periodontitis. In contrast, teeth with apical periodontitis submitted to root canal treatment with calcium hydroxide presented a lower inflammatory cell infiltrate. This group had moderately organized connective tissue, lower prevalence of bacteria, and lower number of MMP-positive cells, similar to healthy teeth submitted to treatment.
  
  
  CONCLUSIONS
  Teeth treated with calcium hydroxide root canal dressing exhibited a lower percentage of bacterial contamination, a lower MMP expression, and a more organized extracellular matrix, unlike those treated in a single visit. This suggests that calcium hydroxide might be beneficial in tissue repair processes.
authors.affiliation: Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan 48109-1078, USA.
authors.forename: Francisco Wanderley Garcia
authors.initials: FW
authors.lastname: Paula-Silva
authors.forename: Léa Assed Bezerra
authors.initials: LA
authors.lastname: da Silva
authors.forename: Yvonne Lorraine
authors.initials: YL
authors.lastname: Kapila
mesh_terms: D000818:Animals; D002126:Calcium Hydroxide / Q000494:pharmacology*; D004195:Disease Models, Animal; D004285:Dogs; D007150:Immunohistochemistry; D007249:Inflammation / Q000188:drug therapy; D020782:Matrix Metalloproteinases / Q000187:drug effects / Q000378:metabolism*; D010485:Periapical Periodontitis / Q000378:metabolism* / Q000628:therapy; D010513:Periodontal Ligament / Q000187:drug effects / Q000378:metabolism; D012387:Root Canal Filling Materials / Q000494:pharmacology*; D012390:Root Canal Therapy / Q000379:methods*; D019227:Tooth Apex / Q000378:metabolism; D016896:Treatment Outcome; D014945:Wound Healing / Q000502:physiology
chemical_list: D012387:Root Canal Filling Materials; D020782:Matrix Metalloproteinases; D002126:Calcium Hydroxide