title: Effect of propionaldehyde or 2,3-butanedione additives on the mechanical properties of Bis-GMA analog-based composites.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of two additives, propionaldehyde/aldehyde or 2,3-butanedione/diketone, on mechanical properties of Bis-GMA-based composites containing TEGDMA, propoxylated Bis-GMA (CH(3)Bis-GMA) or propoxylated fluorinated Bis-GMA (CF(3)Bis-GMA).
  
  
  METHODS
  Three control composites, Bis-GMA/diluent monomer (25/75 mol%), and six test composites, Bis-GMA/diluent monomer/aldehyde or diketone (17/51/32 mol%) were prepared. All composites contained hybrid treated filler (barium aluminosilicate glass/pyrogenic silica; 60 wt%), and 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Degree of conversion (DC%), flexural strength (FS), modulus of elasticity (E), modulus of resilience (R) and diametral tensile strength (DTS) were determined. DC% (n=3) was investigated by FT-IR. For FS and E, beam-shaped specimens (25mm x 2mm x 2mm) were prepared (n=6), stored for 7 days in 37 degrees C deionized water and tested on an Instron utilizing a three-point loading jig (0.5mm/min). The R-values were obtained from the following equation: R=(FS)(2)/2E. For DTS, cylindrical specimens (4mm x 8mm) were prepared (n=6), stored for 7 days in 37 degrees C deionized water and diametrically loaded on an Instron (0.5mm/min). Data were analyzed by one-way ANOVA and Tukey's test (alpha=0.05).
  
  
  RESULTS
  Incorporation of additives led to an increase in DC%, FS and E for Bis-GMA/TEGDMA and Bis-GMA/CH(3)Bis-GMA systems. R-values for all systems were unaffected by addition of additives. They had no significant effect on DC% or mechanical properties of Bis-GMA/CF(3)Bis-GMA.
  
  
  CONCLUSIONS
  The findings correlate with the ability of additives to improve degree of conversion of some composite systems thereby enhancing mechanical properties.
authors.affiliation: Center for Oral and Systemic Diseases, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7455, USA.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Prakki
authors.forename: Patricia Nobrega Rodrigues
authors.initials: PN
authors.lastname: Pereira
authors.forename: Sid
authors.initials: S
authors.lastname: Kalachandra