title: Polymerization shrinkage stresses in a premolar restored with different composite resins and different incremental techniques.
abstract: OBJECTIVE
  To investigate how the incremental filling technique, elastic modulus, and post-gel shrinkage of different dental composite resins affect residual shrinkage stress in a restored premolar.
  
  
  METHODS
  Sixteen composites indicated for restoring posterior teeth were tested. Elastic modulus and Knoop hardness were measured using Knoop indentation tests (n = 10). A strain gauge test was used to measure the post-gel shrinkage (n = 10). Two incremental techniques, horizontal or oblique, were applied in a finite element model of a premolar in combination with the experimentally determined properties to assess the stress conditions along the interface of the restoration and within the material structures. Linear regressions were determined between residual shrinkage stress and the elastic modulus and post-gel shrinkage values.
  
  
  RESULTS
  The mechanical properties and the post-gel shrinkage varied significantly among the composites tested. The calculated shrinkage stress showed a strong correlation with post-gel shrinkage and a weaker correlation with elastic modulus. The oblique incremental filling technique resulted in lower residual shrinkage stress in the enamel and dentin and along the enamel/composite interface compared to the horizontal technique.
  
  
  CONCLUSIONS
  Residual stress varied significantly among the contemporary dental composites indicated for restoring posterior teeth. Shrinkage stress in a restored tooth correlated with post-gel shrinkage. In general, oblique incremental filling resulted in lower residual stresses than did horizontal increments.
authors.affiliation: Department of Operative Dentistry and Dental Materials, Federal University of Uberlandia, Brazil. carlosjsoares@umuarama.ufu.br
authors.forename: Carlos José
authors.initials: CJ
authors.lastname: Soares
authors.forename: Aline Aredes
authors.initials: AA
authors.lastname: Bicalho
authors.forename: Daranee
authors.initials: D
authors.lastname: Tantbirojn
authors.forename: Antheunis
authors.initials: A
authors.lastname: Versluis
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D003188:Composite Resins / Q000737:chemistry*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis / Q000379:methods; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006244:Hardness; D006801:Humans; D016014:Linear Models; D008422:Materials Testing; D058105:Polymerization
chemical_list: D003188:Composite Resins