title: Conjugation of diisocyanate side chains to dimethacrylate reduces polymerization shrinkage and increases the hardness of composite resins.
abstract: OBJECTIVE
  Polymerization shrinkage is one of the main causes of dental restoration failure. This study tried to conjugate two diisocyanate side chains to dimethacrylate resins in order to reduce polymerization shrinkage and increase the hardness of composite resins.
  
  
  METHODS
  Diisocyanate, 2-hydroxyethyl methacrylate, and bisphenol A dimethacrylate were reacted in different ratios to form urethane-modified new resin matrices, and then mixed with 50 wt.% silica fillers. The viscosities of matrices, polymerization shrinkage, surface hardness, and degrees of conversion of experimental composite resins were then evaluated and compared with a non-modified control group.
  
  
  RESULTS
  The viscosities of resin matrices increased with increasing diisocyanate side chain density. Polymerization shrinkage and degree of conversion, however, decreased with increasing diisocyanate side chain density. The surface hardness of all diisocyanate-modified groups was equal to or significantly higher than that of the control group.
  
  
  CONCLUSIONS
  Conjugation of diisocyanate side chains to dimethacrylate represents an effective means of reducing polymerization shrinkage and increasing the surface hardness of dental composite resins.
authors.affiliation: Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Yih-Dean
authors.initials: YD
authors.lastname: Jan
authors.affiliation: Graduate Institute of Oral Biology, National Taiwan University, Taipei, Taiwan; School of Dentistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Bor-Shiunn
authors.initials: BS
authors.lastname: Lee
authors.affiliation: Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan; Graduate Institute of Oral Biology, National Taiwan University, Taipei, Taiwan; School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Lin
authors.affiliation: School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: yeshes@gmail.com.
authors.forename: Wan-Yu
authors.initials: WY
authors.lastname: Tseng
mesh_terms: D000180:Acrylic Resins / Q000138:chemical synthesis* / Q000737:chemistry; D003188:Composite Resins / Q000138:chemical synthesis* / Q000737:chemistry; D006244:Hardness; D017953:Isocyanates / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry*; D058105:Polymerization; D011140:Polyurethanes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D017953:Isocyanates; D008689:Methacrylates; D011140:Polyurethanes
keywords: composite resin; degree of conversion; hardness; polymerization shrinkage; urethane-modified resin