title: Effect of light activation method on flexural properties of dental composites.
abstract: OBJECTIVE
  To determine if irradiating composites in a laboratory tungsten-halogen light-curing unit produced equal flexural properties to stepwise hand-curing with a tungsten-halogen lamp.
  
  
  METHODS
  Bars (n = 10) of nine commercial composites were formed by light-curing in square glass tubes (2 x 2 x 25 mm). Flexure strength (FS, MPa) and flexure modulus (FM, GPa) were tested in three-point bending after aging specimens in water at 37 degrees C for 1 day. Two methods were used to irradiate the composites: a) Triad II (Dentsply) using 40-second exposures from top and bottom; and b) Optilux 400 (Demetron; 600 mW/cm2) using 3 x 40 seconds overlapping exposures from the top only. Filler wt% was determined by thermal gravimetric analysis. The degree of conversion (DC) of each composite cured with the two techniques was evaluated by micro-FTIR. T-tests were performed for FS and FM to compare Triad II vs Optilux for each composite (alpha < 0.05).
  
  
  RESULTS
  There was a trend for Optilux to produce greater FS (significant for A110, Herculite and P60) and FM (significant for all but Clearfil, Esthet-X and Z250), but differences averaged less than 10%. There was no difference in DC between the irradiation modes for any composite.
authors.affiliation: Department of Biomaterials and Biomechanics, Oregon Health & Science University, 611 S.W. Campus Drive, Portland, Oregon 97239, USA. ferracan@ohsu.edu
authors.forename: Jack L
authors.initials: JL
authors.lastname: Ferracane
authors.forename: Lucas L
authors.initials: LL
authors.lastname: Ferracane
authors.forename: Lawrence
authors.initials: L
authors.lastname: Musanje
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D004548:Elasticity; D006801:Humans; D008027:Light; D008029:Lighting / Q000295:instrumentation*; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D015591:Microspectrophotometry; D018583:Pliability; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry
chemical_list: D000180:Acrylic Resins; C112828:Clearfil AP-X; C029012:Composite Dental Resin; D003188:Composite Resins; D003764:Dental Materials; C466112:Esthet-X; C444701:Filtek Z250; D008689:Methacrylates; C443708:P60 Condensible Resin Composite; D011140:Polyurethanes; D019279:Resin Cements; C121818:Tetric ceram; C065770:Herculite XR; C074741:Silux Plus