title: Cuspal flexure, depth-of-cure, and bond integrity of bulk-fill composites.
abstract: OBJECTIVE
  Evaluate cuspal flexure caused by polymerization shrinkage stress, bond integrity, and depth-of-cure of bulk-fill composites.
  
  
  METHODS
  Twenty-eight extracted permanent molars were mounted in stainless steel rings. Slot-shaped Class II mesio-occlusal-distal preparations (four mm deep) were restored with Filtek Supreme Ultra (control; two two-mm increments) and bulk-fill composites (Tetric EvoCeram, Venus, Filtek Bulk Fill). The teeth were digitized using a 3D scanner before and after restoration. Before- and after-restoration scans were aligned, and cuspal flexure was calculated. Bond integrity along occlusal interfaces was assessed by dye penetration and measured after overnight immersion in basic fuchsin dye and cross-sectioning. Depth-of-cure was determined on the cross-sections using Vickers hardness. Statistical analysis was performed with one-way analysis of variance.
  
  
  RESULTS
  All composites caused inward cuspal flexure (10.4 to 13.6 μm). No statistical difference in flexure was found among the composites (P=.07). No significant difference in microhardness at any restoration depths was found for any composite (.35<P<.99). Dye penetration showed comparable bonding along occlusal interfaces for the tested composites.
  
  
  CONCLUSIONS
  Bulk-fill composites cured all the way through four-mm restoration depths. Cuspal flexure, caused by polymerization shrinkage, and bond integrity were not different between teeth restored with the bulk-fill and conventional incrementally placed restorative composites.
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn., USA.
authors.forename: Thuydung
authors.initials: T
authors.lastname: Do
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn., USA.
authors.forename: Brent
authors.initials: B
authors.lastname: Church
authors.affiliation: Department of Restorative Dentistry and Dental Materials, Universidade Federal de Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors.forename: Crisnicaw
authors.initials: C
authors.lastname: Veríssimo
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn., USA.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Hackmyer
authors.affiliation: Department of Restorative Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn., USA.
authors.forename: Daranee
authors.initials: D
authors.lastname: Tantbirojn
authors.affiliation: Department of Restorative Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn., USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Simon
authors.affiliation: Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn., USA. antheun@uthsc.edu.
authors.forename: Antheunis
authors.initials: A
authors.lastname: Versluis
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D004396:Coloring Agents; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification; D003763:Dental Leakage / Q000145:classification; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000145:classification; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008422:Materials Testing; D008963:Molar / Q000648:ultrastructure; D018583:Pliability; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry; D012394:Rosaniline Dyes; D013314:Stress, Mechanical; D013499:Surface Properties; D019228:Tooth Crown / Q000648:ultrastructure*
chemical_list: D004396:Coloring Agents; D003188:Composite Resins; D003764:Dental Materials; C000590992:Filtek Supreme Ultra; D019279:Resin Cements; D012394:Rosaniline Dyes; C501891:Tetric EvoCeram; C488393:Venus (composite resin); C025485:basic fuchsin; C041330:Scotchbond