title: Radiopacity of tantalum oxide nanoparticle filled resins.
abstract: OBJECTIVE
  Radiopacity of composite resins allows radiographic distinction of existing restorations and recurrent caries. Current composites must be supplemented with heavy metal-containing glasses or minerals to achieve a desired radiopacity. The purpose of this study was to evaluate the radiopacity of Tantalum oxide (Ta2O5) filled resins at varying percentage loadings.
  
  
  METHODS
  Methacrylate functionalized Ta2O5 nanoparticles (< 50 nm) in methanol-dissolved or powder forms were mixed into either glycerol dimethacrylate (GDMA) or a bisGMA, TEGDMA, bisEMA mixture (GTE). Specimens were made in a split brass mold (2 x 2 x 15 mm) and compared with an aluminum stepwedge (99.5% pure Al) and a dentin slice of the same thickness. Kodak Ultraspeed periapical X-ray film on a lead plate at a target distance of 45 cm was exposed at 70 kVp and 10 mA, for 0.5 s and processed automatically. Optical density was measured (n = 3) with an RMI Processor Control Densitometer. Radiopacity was calculated as percent relative linear attenuation coefficient (Alpha). ANOVA and Student-Newman-Keuls comparisons were used to determine significance at the 95% confidence level.
  
  
  RESULTS
  Radiopacity increased significantly with Ta2O5 loading (p = 0.001). Ta2O5 nanoparticle filled resins enter the optimal range of diagnostic detectability (alpha = 150-250) at 50 wt.% and approach equivalence with enamel at approximately 70 wt.%.
  
  
  CONCLUSIONS
  The introduction of tantalum oxide nanoparticle filler has potential as a miscible component of a resin composite to provide radiopacity for microfiller-type restorative materials and to circumvent the need for hydrolysis-prone glass reinforcing fillers.
authors.affiliation: Medical College of Georgia, School of Dentistry, Augusta 30912, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: Chan
authors.forename: H W
authors.initials: HW
authors.lastname: Titus
authors.forename: K H
authors.initials: KH
authors.lastname: Chung
authors.forename: H
authors.initials: H
authors.lastname: Dixon
authors.forename: S T
authors.initials: ST
authors.lastname: Wellinghoff
authors.forename: H R
authors.initials: HR
authors.lastname: Rawls
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003287:Contrast Media; D008689:Methacrylates / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D011861:Radiography, Dental; D013635:Tantalum / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D003287:Contrast Media; D008689:Methacrylates; D010087:Oxides; D013635:Tantalum; C078151:tantalum oxide