title: Low shrinkage light curable nanocomposite for dental restorative material.
abstract: OBJECTIVE
  The aim of this study was to develop a low shrinkage visible light curable nanocomposite dental restorative material without sacrificing the other properties of conventional materials. This nanocomposite was developed by using an epoxy resin 3,4-epoxycyclohexylmethyl-(3,4-epoxy)cyclohexane carboxylate (ERL4221) matrix with 55% wt of 70-100 nm nanosilica fillers through ring-opening polymerization. GPS (gamma-glycidoxypropyl trimethoxysilane) was used to modify the surfaces of silica nanoparticles.
  
  
  RESULTS
  The nanocomposite was shown to exhibit low polymerization shrinkage strain, which is only a quarter of currently used methacrylate-based composites. It also exhibited a low thermal expansion coefficient of 49.8 microm/m degrees C which is comparable to that of the methacrylate based composites (51.2 microm/m degrees C). The strong interfacial interactions between the resin and fillers at nanoscales were demonstrated by an observed high strength and high thermal stability of the nanocomposite. A microhardness of 62 KHN and a tensile strength of 47 MPa were reached. A high degree of conversion ( approximately 70%) can be obtained after less than 60 s of irradiation upon the nanocomposite. A transmission electron microscope (TEM) study of the nanocomposite showed no aggregation of fillers. Comparable results to the methacrylate based composites were obtained from the one day MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) cytotoxicity test.
  
  
  CONCLUSIONS
  The developed epoxy resin based nanocomposite demonstrated low shrinkage and high strength and is suitable for dental restorative material applications.
authors.affiliation: National Taiwan University Hospital, Taipei, Taiwan, ROC; School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Min-Huey
authors.initials: MH
authors.lastname: Chen
authors.forename: Ci-Rong
authors.initials: CR
authors.lastname: Chen
authors.forename: Seng-Haw
authors.initials: SH
authors.lastname: Hsu
authors.forename: Shih-Po
authors.initials: SP
authors.lastname: Sun
authors.forename: Wei-Fang
authors.initials: WF
authors.lastname: Su
mesh_terms: D004396:Coloring Agents; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D003509:Cyclohexanecarboxylic Acids / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D004853:Epoxy Resins / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D011108:Polymers; D012821:Silanes / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D012822:Silicon Dioxide / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013778:Tetrazolium Salts; D013816:Thermodynamics; D013844:Thiazoles
chemical_list: D004396:Coloring Agents; D003188:Composite Resins; D003509:Cyclohexanecarboxylic Acids; D004853:Epoxy Resins; D011108:Polymers; D012821:Silanes; D013778:Tetrazolium Salts; D013844:Thiazoles; C013353:EP 201; C039462:gamma-glycidoxypropyltrimethoxysilane; D012822:Silicon Dioxide; C022616:thiazolyl blue