title: Variability of physicochemical properties of an epoxy resin sealer taken from different parts of the same tube.
abstract: OBJECTIVE
  To analyse several physicochemical properties of AH Plus (Dentsply DeTrey, Konstanz, Germany), including setting time, flow, radiopacity and the degree of conversion (DC); and to correlate the results with the source of the material: from the beginning, middle or end of the tubes in which they were supplied.
  
  
  METHODS
  Three experimental groups were established for each property investigated. Group 1 corresponded to material taken from the beginning of tubes A and B; Group 2 corresponded to material taken from the middle of each tube; and group 3 corresponded to that from the end of each tube. The setting time, flow and radiopacity were studied according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 57. DC was determined from infrared spectra, which were recorded at 1-h intervals for the first 6 h; then, at 2-h intervals for the next 14 h; then, at 24 and 30 h. Data were analysed statistically by analysis of variance (anova), Tukey-Kramer, Kruskal-Wallis and Dunn tests, with a significance level of 5%.
  
  
  RESULTS
  Group 1 had a significantly longer setting time (2303 ± 1058 min) (P < 0.05). Group 3 had the lowest flowability (30.0 ± 0.7 mm) and the highest radiopacity (14.85 ± 1.8 mm Al) (P < 0.05). No differences were found for the DC test (P > 0.05).
  
  
  CONCLUSIONS
  The results suggest that segregation occurs between the organic and inorganic components of AH Plus sealer, thereby changing the setting time, flow and radiopacity.
authors.affiliation: Department of Operative Dentistry, Dental Materials and Endodontics Bauru Dental School, University of São Paulo, Bauru, Brazil. jarcio@usp.br
authors.forename: J V
authors.initials: JV
authors.lastname: Baldi
authors.forename: R A
authors.initials: RA
authors.lastname: Bernardes
authors.forename: M A H
authors.initials: MA
authors.lastname: Duarte
authors.forename: R
authors.initials: R
authors.lastname: Ordinola-Zapata
authors.forename: B C
authors.initials: BC
authors.lastname: Cavenago
authors.forename: J C S
authors.initials: JC
authors.lastname: Moraes
authors.forename: I G
authors.initials: IG
authors.lastname: de Moraes
mesh_terms: D000704:Analysis of Variance; D055598:Chemical Phenomena; D003287:Contrast Media; D004853:Epoxy Resins / Q000737:chemistry* / Q000592:standards; D057446:Hydrodynamics; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry* / Q000592:standards; D012387:Root Canal Filling Materials / Q000737:chemistry* / Q000592:standards
chemical_list: D003287:Contrast Media; D004853:Epoxy Resins; D019279:Resin Cements; D012387:Root Canal Filling Materials; C534916:epoxy resin-based root canal sealer