title: Effect of light-emitting diode photopolymerization modes on the push-out bond strength of a methacrylate-based sealer.
abstract: BACKGROUND
  The objective of this study was to investigate and compare the effect of different light-emitting diode (LED) polymerization modes on the bond strength of a methacrylate-based sealer used with Resilon or gutta-percha.
  
  
  METHODS
  Forty extracted single-rooted teeth were sectioned off below the cementoenamel junction, and the root canals were instrumented by using rotary instruments to ISO #30/0.06 taper. The roots were randomly assigned into 1 of the following groups for root canal obturation: (1) RealSeal + Resilon and (2) RealSeal + gutta-percha. In each group, specimens were further subgrouped according to the LED polymerization mode used to cure RealSeal: (1) standard (20 seconds of maximum intensity) and (2) exponential (5 seconds of exponential power increase, followed by 15 seconds of maximum intensity). Specimens were stored in 100% humidity for 1 week at 37 °C. Push-out test was performed at a crosshead speed of 1 mm/min on 2-mm-thick root slices obtained from coronal to apical direction. Multivariate analysis of variance and Tukey tests were used for statistical analysis of the data (P=.05). Failure modes were examined under the scanning electron microscope.
  
  
  RESULTS
  The tested polymerization modes had no significant effect on the bond strength values (P > .05). RealSeal + gutta-percha yielded significantly greater bond strength than RealSeal + Resilon (P < .05). In all groups, the bond strength values decreased significantly from coronal to apical direction (P < .05). Adhesive failure at the sealer-dentin interface was the predominant fracture mode.
  
  
  CONCLUSIONS
  The exponential photopolymerization mode had no significant advantage over the standard regimen in terms of dentin bond strength.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Hacettepe University, Ankara, Turkey. enagas@hacettepe.edu.tr
authors.forename: Emre
authors.initials: E
authors.lastname: Nagas
authors.forename: Zafer C
authors.initials: ZC
authors.lastname: Cehreli
authors.forename: Veli
authors.initials: V
authors.lastname: Durmaz
mesh_terms: D000268:Adhesiveness; D003188:Composite Resins / Q000737:chemistry*; D055117:Curing Lights, Dental / Q000145:classification*; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure; D004492:Edetic Acid / Q000627:therapeutic use; D006171:Gutta-Percha / Q000737:chemistry; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D055668:Photochemical Processes; D058105:Polymerization; D011829:Radiation Dosage; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012388:Root Canal Irrigants / Q000627:therapeutic use; D012389:Root Canal Obturation / Q000379:methods; D018915:Root Canal Preparation / Q000379:methods; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors
chemical_list: D003188:Composite Resins; C511498:Real Seal composite resin; D012387:Root Canal Filling Materials; D012388:Root Canal Irrigants; C486892:resilon sealer; D006171:Gutta-Percha; D004492:Edetic Acid; D012973:Sodium Hypochlorite