title: Effect of a two-step placement procedure on the dislocation resistance of a methacrylate resin-based root canal sealer: a proof of concept.
abstract: OBJECTIVE
  To investigate whether the placement of a methacrylate root canal sealer or a conventional epoxy root canal sealer in two steps increases their dislocation resistance when compared to a one-step placement procedure.
  
  
  METHODS
  Eighty single-rooted teeth were randomly allocated to 4 groups (n=20). All canals were instrumented to size 40, 0.06 taper and irrigated according to a standardized protocol. Root canal filling was conducted as follows: group 1: methacrylate sealer placed in two steps; group 2: methacrylate sealer placed in one step; group 3: epoxy sealer placed in two steps; group 4: epoxy sealer placed in one step. After setting, thin slices at different root levels were obtained and submitted to push-out testing. RESULTS were analyzed with non-parametric tests to compare the two-step procedures to their one-step counterparts. Failure modes were determined by stereomicroscopy. Random untested methacrylate sealer specimens were also examined with scanning electron microscopy.
  
  
  RESULTS
  At each root level, dislocation resistance was significantly higher for the two-step procedure than for the one-step procedure using the methacrylate sealer (p=0.003, p=0.005, p<0.001) but not the epoxy sealer (p=0.83, p=0.1, p=0.06). Among root levels, there were no significant differences in dislocation resistance in the methacrylate sealer two-step group, while all other groups showed differences.
  
  
  CONCLUSIONS
  A two-step placement procedure resulted in significantly higher dislocation resistance for the methacrylate sealer but not for the epoxy sealer.
authors.forename: Amir T
authors.initials: AT
authors.lastname: Moinzadeh
authors.forename: Hesam
authors.initials: H
authors.lastname: Mirmohammadi
authors.forename: Tjibbe
authors.initials: T
authors.lastname: Veenema
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: Kleverlaan
authors.forename: Paul R
authors.initials: PR
authors.lastname: Wesselink
authors.forename: Min-Kai
authors.initials: MK
authors.lastname: Wu
authors.forename: Hagay
authors.initials: H
authors.lastname: Shemesh
mesh_terms: D000465:Algorithms; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003786:Dental Pulp Cavity / Q000648:ultrastructure; D003799:Dental Stress Analysis / Q000295:instrumentation; D004853:Epoxy Resins / Q000737:chemistry; D006801:Humans; D006813:Humidity; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008689:Methacrylates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012389:Root Canal Obturation / Q000295:instrumentation / Q000379:methods*; D018915:Root Canal Preparation / Q000379:methods; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D003188:Composite Resins; D004853:Epoxy Resins; D008689:Methacrylates; C511498:Real Seal composite resin; D012387:Root Canal Filling Materials; C534916:epoxy resin-based root canal sealer