title: Effect of chelating solutions on the microhardness of root canal lumen dentin.
abstract: BACKGROUND
  The greatest reduction in microhardness of the most superficial layer of dentin of the root canal lumen is desired. The use of chelating agents during biomechanical preparation of root canals removes smear layer, increasing the access of the irrigant into the dentin tubules to allow adequate disinfection, and also reduces dentin microhardness, facilitating the action of endodontic instruments. This study evaluated the effect of different chelating solutions on the microhardness of the most superficial dentin layer from the root canal lumen.
  
  
  METHODS
  Thirty-five recently extracted single-rooted maxillary central incisors were instrumented, and the roots were longitudinally sectioned in a mesiodistal direction to expose the entire canal extension. The specimens were distributed in seven groups according to the final irrigation: 15% EDTA, 10% citric acid, 5% malic acid, 5% acetic acid, apple vinegar, 10% sodium citrate, and control (no irrigation). A standardized volume of 50 μL of each chelating solution was used for 5 minutes. Dentin microhardness was measured with a Knoop indenter under a 10-g load and a 15-second dwell time. Data were analyzed statistically by one-way analysis of variance and Tukey-Kramer multiple-comparison test at 5% significance level.
  
  
  RESULTS
  EDTA and citric acid had the greatest overall effect, causing a sharp decrease in dentin microhardness without a significant difference (p > .05) from each other. However, both chelators differed significantly from the other solutions (p < .001). Sodium citrate and deionized water were similar to each other (p > .05) and did not affect dentin microhardness. Apple vinegar, acetic acid, and malic acid were similar to each other (p > .05) and presented intermediate results.
  
  
  CONCLUSIONS
  Except for sodium citrate, all tested chelating solutions reduced microhardness of the most superficial root canal dentin layer. EDTA and citric acid were the most efficient.
authors.affiliation: Department of Endodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. cruz@forp.usp.br
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Cruz-Filho
authors.forename: Manoel D
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: Ricardo Novak
authors.initials: RN
authors.lastname: Savioli
authors.forename: Ricardo Gariba
authors.initials: RG
authors.lastname: Silva
authors.forename: Luiz Pascoal
authors.initials: LP
authors.lastname: Vansan
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology*; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid / Q000494:pharmacology; D003786:Dental Pulp Cavity / Q000187:drug effects* / Q000473:pathology; D003804:Dentin / Q000187:drug effects* / Q000473:pathology; D004492:Edetic Acid / Q000494:pharmacology; D006244:Hardness; D006801:Humans; D007180:Incisor / Q000187:drug effects / Q000473:pathology; D008293:Malates / Q000494:pharmacology; D008422:Materials Testing; D012388:Root Canal Irrigants / Q000008:administration & dosage / Q000494:pharmacology*; D018915:Root Canal Preparation / Q000295:instrumentation; D016369:Smear Layer; D000077559:Sodium Citrate; D012973:Sodium Hypochlorite / Q000008:administration & dosage; D013997:Time Factors; D014867:Water
chemical_list: D002614:Chelating Agents; D002951:Citrates; D008293:Malates; D012388:Root Canal Irrigants; D014867:Water; D000077559:Sodium Citrate; D019343:Citric Acid; C030298:malic acid; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D019342:Acetic Acid