title: Shrinkage, stress, and modulus of dimethacrylate, ormocer, and silorane composites.
abstract: OBJECTIVE
  to evaluate the shrinkage, polymerization stress, elastic and bulk modulus resulting from composites formulated by siloranes, 2(nd) generation ormocers, and dimethacrylates.
  
  
  METHODS
  The bonded disc method was used to evaluate volumetric shrinkage. The polymerization stress was evaluated by mean of the Bioman. Cylindrical specimens (5 mm thickness and 6 mm diameter) were submitted to gradual loading. Young's and bulk modulus were obtained from the slope of the stress/strain curve. Data were analyzed using one-way analysis of variance and Tukey's test (5%).
  
  
  RESULTS
  Grandio and ormocer showed significant higher elastic and bulk modulus. Silorane presented significant lowest bulk modulus and maximum shrinkage. Ormocer and silorane presented lower values for the maximum rate of shrinkage. Extra-low shrinkage (ELS) composite presented the greatest maximum shrinkage. The higher maximum rate of shrinkage was attained by Grandio and ELS, statistically similar from each other. The silorane showed lower values of maximum stress and maximum rate of stress. The higher values of maximum stress were presented by ELS and Grandio, statistical similar between them. Grandio showed the significantly greatest maximum rate of stress.
  
  
  CONCLUSIONS
  Silorane showed to promote lower shrinkage/stress among the composites, with the lowest elastic modulus. Ormocer showed lower shrinkage/stress than methacrylates despite of its high modulus.
authors.affiliation: Department of Prosthetic Dentistry, School of Dentistry, Meridional Faculty - IMED, Passo Fundo, RS, Brazil.
authors.forename: Atais
authors.initials: A
authors.lastname: Bacchi
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, Federal University of Ceará, Fortaleza, Ceará, Brazil.
authors.forename: Victor Pinheiro
authors.initials: VP
authors.lastname: Feitosa
authors.affiliation: Department of Clinic, School of Dentistry, Veiga de Almeida University - UVA, Rio de Janeiro, Brazil.
authors.forename: Andrea Soares Quirino
authors.initials: AS
authors.lastname: da Silva Fonseca
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, Fluminense Federal University, Rio de Janeiro, Brazil.
authors.forename: Larissa Maria Assad
authors.initials: LM
authors.lastname: Cavalcante
authors.affiliation: Biomaterials Science Research Group, School of Dentistry, University of Manchester, Manchester, United Kingdom.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Silikas
authors.affiliation: Department of Clinic, School of Dentistry, Veiga de Almeida University - UVA, Rio de Janeiro, Brazil.
authors.forename: Luis Felipe Jochins
authors.initials: LF
authors.lastname: Schneider
keywords: Composite resin; polymerization stress; volumetric shrinkage