title: Mechanical properties of visible light-cured resins reinforced with hydroxyapatite for dental restoration.
abstract: OBJECTIVE
  The purpose of this study was to measure and analyze the mechanical properties of several composite materials designed for dental restoration.
  
  
  METHODS
  The materials were composed of a visible light-curing monomer mixture (either Bis-GMA+TEGDMA or Bis-GMA+HEMA) as a matrix and hydroxyapatite (either microscopic or nanoscopic particles) as a reinforcing filler. The surface of the hydroxyapatite particles was modified by using a coupling agent (citric, malic, acrylic or methacrylic acid). Five specimens of 14 different composites were prepared for each mechanical test: flexural strength, Young's modulus and Vickers hardness. Mean values and standard deviations were calculated, and ANOVA and Student Newman Keuls multiple comparison tests were applied (P < 0.05).
  
  
  RESULTS
  The addition of 50-60 wt% of hydroxyapatite particles to the unfilled monomer mixtures led to the increase of both Young's modulus and surface hardness of the material, while the flexural strength decreased. In general, when microscopic instead of nanoscopic hydroxyapatite was used as a reinforcing filler, mechanical properties were favored. The mechanical properties were also improved by adding citric, acrylic or methacrylic acid as a coupling agent.
  
  
  CONCLUSIONS
  An adequate surface modification of the hydroxyapatite particles conferred enhanced mechanical properties to the final dental composite. Microscopic-hydroxyapatite particles are preferred to nanoscopic ones.
authors.affiliation: Institut de Ciència de Materials de Barcelona, Campus de la UAB, Bellaterra, Spain.
authors.forename: Raul W
authors.initials: RW
authors.lastname: Arcís
authors.forename: Anabel
authors.initials: A
authors.lastname: López-Macipe
authors.forename: Manuel
authors.initials: M
authors.lastname: Toledano
authors.forename: Estrella
authors.initials: E
authors.lastname: Osorio
authors.forename: Rafael
authors.initials: R
authors.lastname: Rodríguez-Clemente
authors.forename: Jaime
authors.initials: J
authors.lastname: Murtra
authors.forename: Maria A
authors.initials: MA
authors.lastname: Fanovich
authors.forename: Concepción Domingo
authors.initials: CD
authors.lastname: Pascual
mesh_terms: D000179:Acrylates / Q000737:chemistry; D000269:Adhesives / Q000737:chemistry; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D019343:Citric Acid / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent; D017886:Durapatite / Q000737:chemistry*; D004548:Elasticity; D006244:Hardness; D006801:Humans; D008027:Light; D008293:Malates / Q000737:chemistry; D008422:Materials Testing; D019563:Mechanics; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D013223:Statistics as Topic; D013499:Surface Properties
chemical_list: D000179:Acrylates; D000269:Adhesives; D003188:Composite Resins; D003764:Dental Materials; D008293:Malates; D008689:Methacrylates; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; C008384:methacrylic acid; D019343:Citric Acid; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C005044:hydroxyethyl methacrylate; C030298:malic acid; D017886:Durapatite; C036658:acrylic acid