title: Microleakage evaluation of a new low-shrinkage composite restorative material.
abstract: OBJECTIVE
  This study compared the microleakage of an experimental low-shrinkage resin composite (Hermes), a nanofilled resin composite material (Filtek Supreme) and a hybrid resin composite (Tetric Ceram) using a dye penetration method.
  
  
  METHODS
  Class I cavities prepared in 60 human molars were randomly divided into 3 groups according to the restorative material used. The preparations were restored using a bulk or an incremental technique. Half of the specimens from each group were subjected to 200,000 cycles of loading at 50 N, while the other half were stored in distilled water for 24 hours at 37 degrees C. All specimens were immersed in 1% methylene blue (pH = 7.0) for 24 hours and sectioned into 3 slabs. The margins were evaluated for microleakage using an ordinal scoring system (0-4) under a stereomicroscope at 40x magnification. Data were subjected to the non-parametric Kruskal-Wallis analysis of variance and Mann-Whitney test (p<0.05). Data were expressed as median leakage scores and mean ranks.
  
  
  RESULTS
  All of the restorative systems had microleakage, regardless of the insertion technique and mechanical load cycling. Incremental placement significantly reduced microleakage as compared to the bulk technique, regardless of the restorative system used. Load cycling significantly affected incrementally placed restorations, except for the Hermes system.
authors.affiliation: Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC 27599, USA. paulayamazaki@hotmail.com
authors.forename: Paula C V
authors.initials: PC
authors.lastname: Yamazaki
authors.forename: Ana Karina B
authors.initials: AK
authors.lastname: Bedran-Russo
authors.forename: Patricia N R
authors.initials: PN
authors.lastname: Pereira
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Wsift
mesh_terms: D003188:Composite Resins; D003763:Dental Leakage / Q000517:prevention & control*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D008963:Molar; D053761:Nanocomposites; D044367:Phase Transition
chemical_list: D003188:Composite Resins; C474035:Filtek Supreme; C516831:Hermes Composite Resin; C121818:Tetric ceram