title: [Comparative study of polymerization shrinkage and related properties of flowable composites and an unfilled resin].
abstract: OBJECTIVE
  The polymerization shrinkage and shrinkage stress of dental composites are in the center of the interest of researchers and manufacturers. It is a great challenge to minimize this important property as low as possible. Many factors are related and are in complicated correlation with each other affecting the polymerization shrinkage. Polymerization shrinkage stress degree of conversion and elasticity has high importance from this aspect. Our aim was to study the polymerization shrinkage and related properties (modulus of elasticity, degree of conversion, shrinkage stress) of three flowable composite (Charisma Opal Flow, SDR, Filtek Ultimate) and an unfilled composite resin.
  
  
  METHODS
  Modulus of elasticity was measured using three point flexure tests on universal testing machine. The polymerization shrinkage stress was determined using bonded-disc technique. The degree of conversion measurements were performed by FT-IR spectroscopy. And the volumetric shrinkage was investigated using Archimedes principle and was measured on analytical balance with special additional equipment.
  
  
  RESULTS
  The unfilled resin generally showed higher shrinkage (8,26%), shrinkage stress (0,8 MPa) and degree of conversion (38%), and presented the lowest modulus of elasticity (3047,02MPa).
  
  
  CONCLUSIONS
  Highest values of unfilled resin correspond to the literature. The lack of fillers enlarges the shrinkage, and the shrinkage stress, but gives the higher flexibility and higher degree of conversion. Further investigations needs to be done to understand and reveal the differences between the composites.
authors.forename: Katalin
authors.initials: K
authors.lastname: Bukovinszky
authors.forename: Lilla
authors.initials: L
authors.lastname: Molnár
authors.forename: József
authors.initials: J
authors.lastname: Bakó
authors.forename: Melinda
authors.initials: M
authors.lastname: Szalóki
authors.forename: Csaba
authors.initials: C
authors.lastname: Hegedus
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D004548:Elasticity; D006801:Humans; D058105:Polymerization; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: C084111:Charisma composite resin; D003188:Composite Resins; C111840:flowable hybrid composite