title: Nano-porous thermally sintered nano silica as novel fillers for dental composites.
abstract: OBJECTIVE
  The study evaluates properties of an experimental dental composite consisting of a porous thermally sintered nano-silica as filler. The properties are compared with those of an experimental composite containing micro fillers and a commercially available nano-composite, Filtek Supreme(®) Translucent. Different models are used to predict the elastic modulus and strength of the composites.
  
  
  METHODS
  Nano-silica with primary particles of 12 nm was thermally sintered to form nanoporous filer particles. The experimental composites were prepared by incorporating 70 wt.% of the fillers into a mixture of Bis-GMA and TEGDMA as matrix phase. Having added photoinitiator system the composites were inserted into the test molds and light-cured. The microfiller containing composites were also prepared using micron size glass fillers. Degree of conversion (DC%) of the composites was measured using FTIR spectroscopy. Diametral tensile strength (DTS), flexural strength, flexural modulus and fracture toughness were measured. SEM was utilized to study the cross section of the fractured specimens. The surface topography of the specimens was investigated using atomic force microscopy (AFM). The specific surface area of the sintered nano silica was measured using BET method. The data were analyzed and compared by ANOVA and Tukey HSD tests (significance level=0.05).
  
  
  RESULTS
  The results showed improvements in flexural modulus and fracture toughness of the composites containing sintered filler. AFM revealed a lower surface roughness for sintered silica containing composites. No significant difference was observed between DTS, DC%, and flexural strength of the sintered nanofiller composite and the Filtek Supreme(®). The results also showed that the modulus of the composite with sintered filler was higher than the model prediction.
  
  
  CONCLUSIONS
  The thermally sintered nano-porous silica fillers significantly enhanced the mechanical properties of dental composites introducing a new approach to develop materials with improved properties.
authors.affiliation: Iran Polymer and Petrochemical Institute, P.O. Box 14965/115, Tehran, Iran. M.Atai@ippi.ac.ir
authors.forename: Mohammad
authors.initials: M
authors.lastname: Atai
authors.forename: Ayoub
authors.initials: A
authors.lastname: Pahlavan
authors.forename: Niloofar
authors.initials: N
authors.lastname: Moin
mesh_terms: D000465:Algorithms; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D055598:Chemical Phenomena; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D055119:Elastic Modulus; D005898:Glass / Q000737:chemistry; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D058567:Photoinitiators, Dental / Q000737:chemistry; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D016062:Porosity; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C500649:Filtek Supreme Translucent; D008689:Methacrylates; D058567:Photoinitiators, Dental; D011109:Polymethacrylic Acids; D012821:Silanes; C020946:triethylene glycol dimethacrylate; C017492:methacryloxypropyltrimethoxysilane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide