title: Multiple correlations of material parameters of light-cured dental composites.
abstract: OBJECTIVE
  The aim of this study was to explore the correlations between the Knoop hardness, Young's modulus, viscosity, and polymerization shrinkage of an experimental dental composite, in order to determine the temporal variations of the material properties during the polymerization process.
  
  
  METHODS
  The digital image correlation method was employed to measure the polymerization shrinkage along the curing depth of bar-shape specimens (cross-section 4mmx2mm and length 10mm) of an experimental composite RZE045. The shrinkage data were correlated with the Knoop microhardness measured on specimens prepared in consistent conditions. Another series of tests were performed on cuboid composite samples (cross-section 4mmx4mm and height 5mm) with different degrees of conversions to determine the correlations among microhardness, Young's modulus and viscosity. Further correlations between shrinkage, Young's modulus and viscosity were then derived, from which the temporal variations of the mechanical parameters during curing were estimated.
  
  
  RESULTS
  Along the curing depth, the Knoop microhardness of the experimental composite RZE045 decreased more rapidly than its volumetric shrinkage. A power function was employed to describe their relation. On the other hand, Knoop microhardness was found to be proportional to Young's modulus and viscosity. These linear correlations also seemed to be applicable to other materials including unfilled resins, silica glass and other dental composites.
  
  
  CONCLUSIONS
  Correlations between material parameters of dental composites allowed the rapid temporal variations of Young's modulus and viscosity during curing to be estimated based on the measured polymerization shrinkage-strain history.
authors.affiliation: Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, MN, USA.
authors.forename: Jianying
authors.initials: J
authors.lastname: Li
authors.forename: Haiyan
authors.initials: H
authors.lastname: Li
authors.forename: Alex S L
authors.initials: AS
authors.lastname: Fok
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D017609:Barium Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D055119:Elastic Modulus; D005898:Glass / Q000737:chemistry; D006244:Hardness; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008027:Light; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012826:Silicone Elastomers / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors; D014783:Viscosity
chemical_list: D000538:Aluminum Silicates; D017609:Barium Compounds; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011091:Polyesters; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C543924:RZE045 resin; D012821:Silanes; D017640:Silicates; D012826:Silicone Elastomers; D013729:Terpenes; C415406:barium borosilicate; C102738:barium glass filler; C507210:premise composite resin; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; C017492:methacryloxypropyltrimethoxysilane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; D012822:Silicon Dioxide