title: Chitosan: a new solution for removal of smear layer after root canal instrumentation.
abstract: OBJECTIVE
  To evaluate, by scanning electron microscopy (SEM), the efficacy of smear layer removal using chitosan compared with different chelating agents, and to quantify, by atomic absorption spectrophotometry with flame (AASF), the concentration of calcium ions in these solutions after irrigation.
  
  
  METHODS
  The root canals of twenty-five canines were prepared using a crown-down technique and irrigated with 1% sodium hypochlorite. The teeth were randomly divided into groups (n = 5), according to the type of final irrigation: 15% EDTA, 0.2% chitosan, 10% citric acid, 1% acetic acid and control (without final irrigation). The total volume of each chelating solution was collected from the canals and analysed by AASF for quantification of calcium ions in the solutions. Then, the roots were split longitudinally and examined by SEM for evaluation of smear layer removal in the middle and apical thirds. Cleaning scores were attributed and analysed statistically using the Kruskal-Wallis and Dunn tests. The AASF data were analysed by one-way anova and Tukey-Kramer test. A significant level of α = 0.05 was adopted.
  
  
  RESULTS
  15% EDTA, 0.2% chitosan and 10% citric acid had similar smear layer removal capacity with a significant difference (P < 0.05) from 1% acetic acid and the control group. There was no significant difference (P > 0.05) between the smear layer remaining in the middle and apical thirds. The highest calcium ion concentration was observed with 15% EDTA (121.80 ± 5.13) and 0.2% chitosan (104.13 ± 19.23), with no significant difference. The lowest calcium ion concentration was obtained with 1% acetic acid (25.62 ± 7.68), whilst 10% citric acid (70.38 ± 11.15) had intermediate results, differing significantly from the other solutions (P < 0.01).
  
  
  CONCLUSIONS
  15% EDTA, 0.2% chitosan and 10% citric acid effectively removed smear layer from the middle and apical thirds of the root canal. 15% EDTA and 0.2% chitosan were associated with the greatest effect on root dentine demineralization, followed by 10% citric acid and 1% acetic acid.
authors.affiliation: Department of Restorative Dentistry, Ribeirão Preto School of Dentistry, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: P V
authors.initials: PV
authors.lastname: Silva
authors.forename: D F C
authors.initials: DF
authors.lastname: Guedes
authors.forename: F V
authors.initials: FV
authors.lastname: Nakadi
authors.forename: J D
authors.initials: JD
authors.lastname: Pécora
authors.forename: A M
authors.initials: AM
authors.lastname: Cruz-Filho
mesh_terms: D019342:Acetic Acid; D000704:Analysis of Variance; D002118:Calcium / Q000032:analysis; D002614:Chelating Agents; D048271:Chitosan; D019343:Citric Acid; D004492:Edetic Acid; D006801:Humans; D008855:Microscopy, Electron, Scanning; D012388:Root Canal Irrigants; D018915:Root Canal Preparation / Q000379:methods*; D016369:Smear Layer; D013054:Spectrophotometry, Atomic / Q000379:methods; D018709:Statistics, Nonparametric
chemical_list: D002614:Chelating Agents; D012388:Root Canal Irrigants; D019343:Citric Acid; D048271:Chitosan; D004492:Edetic Acid; D019342:Acetic Acid; D002118:Calcium