title: The influence of monomeric resin and filler characteristics on the performance of experimental resin-based composites (RBCs) derived from a commercial formulation.
abstract: OBJECTIVE
  To explore experimental RBCs derived from a successful commercially available RBC (Grandio) to investigate resin monomer blend and filler parameters (volume fraction, density and diameter) on RBC performance.
  
  
  METHODS
  Six experimental RBCs modified from a commercial RBC were tested. The three-point flexure strength (σ(3)) and modulus (E) data was determined for groups of 20 bar-shaped specimens, prepared in a custom-made knife-edge split aluminum mold and irradiated using a modification of the ISO 4049 protocol. The biaxial flexure strength (BFS) and top and bottom Vickers hardness number (VHN) determination was performed on disc-shaped specimens (n=20). Normal distribution of the σ(3), E, BFS and top and bottom VHN data was verified using the Shapiro-Wilk's test. Paired groups were compared using independent samples t-test for the individual tests investigated (σ(3), E, BFS and top and bottom VHN) at a significance level of P<0.05.
  
  
  RESULTS
  A significant decrease in the mean σ(3) (P<0.011) and mean E (P<0.001) were identified on increasing the filler fraction (from 71.4 to 74.5 vol%) or increasing the mean filler diameter (from 1.5 to 2.5 μm). Increasing the filler density resulted in a significant increase in the mean σ(3) (P<0.001), mean E (P<0.001) and mean top VHN (P≤0.001). Replacing the monomeric blend with an ormocer blend significantly reduced the mean σ(3), E, BFS and top and bottom VHNs (all P<0.001).
  
  
  CONCLUSIONS
  For each RBC monomeric resin and filler (type, density and diameter) combination employed, a finite filler volume fraction exists. Operating at the finite filler volume fraction increases the difficulty in improving the mechanical properties of the RBCs tailored from a commercial product.
authors.affiliation: Regensburg University Medical Center, Department of Prosthetic Dentistry, Regensburg, Germany. Sebastian.Hahnel@klinik.uni-regensburg.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hahnel
authors.forename: Adam H
authors.initials: AH
authors.lastname: Dowling
authors.forename: Samy
authors.initials: S
authors.lastname: El-Safty
authors.forename: Garry J P
authors.initials: GJ
authors.lastname: Fleming
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins / Q000138:chemical synthesis* / Q000737:chemistry*; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D006244:Hardness; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D010316:Particle Size; D018583:Pliability; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D012821:Silanes
chemical_list: D003188:Composite Resins; C509998:Grandio; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D012821:Silanes; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate