title: Influence of artificial aging on the fracture strength and stiffness of Targis/Vectris fixed partial dentures.
abstract: OBJECTIVE
  To evaluate the effect of artificial aging on the fracture strength and stiffness of fiber-reinforced composite fixed partial dentures (FPDs).
  
  
  METHODS
  Twelve FPDs were replicated using Targis/Vectris resin composite (Ivoclar Vivadent) and randomly divided in 2 groups. Group A was artificially aged for 900 hours in a weathering machine using dry/wet cycles and 534 W/m2 irradiations with wavelengths ranging from 300 to 800 nm. Group B (control) was stored in 100% relative humidity at 37 degrees C +/- 1 degree C for 900 hours. The FPDs were luted on metal abutments with Variolink II resin cement (Ivoclar Vivadent). The flexure stress was applied on the pontic at a descending speed of 1.0 mm/min until complete failure. Fracture strength, stiffness, and number of cracks produced on the FPDs were statistically analyzed.
  
  
  RESULTS
  Targis veneering material in the control group fractured at a mean of 913 +/- 130 N, whereas in the aged group it failed at a mean of 722 +/- 154 N (P = .042). The mean fracture load of aged FPD frameworks was slightly lower than that of the controls: 1,532 +/- 237 N and 1,578 +/- 257 N, respectively (P = .758). The stiffness at 400 N was not significantly different between the 2 groups. The number of cracks at Targis failure was higher in aged groups.
  
  
  CONCLUSIONS
  Accelerated aging significantly reduced the strength of the Targis veneering composite, increasing its brittleness; however, it had no effect on the inner Vectris framework.
authors.affiliation: Department of Dental Sciences, Section of Prosthodontics, Alma Mater Studiorum, University of Bologna, Italy. PB.dos@med.unibo.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Baldissara
authors.forename: Candida
authors.initials: C
authors.lastname: Parisi
authors.forename: Carlo
authors.initials: C
authors.lastname: Monaco
authors.forename: Roberto
authors.initials: R
authors.lastname: Scotti
mesh_terms: D019245:Compressive Strength; D003764:Dental Materials / Q000737:chemistry*; D019232:Dental Restoration Failure; D003830:Denture, Partial, Fixed; D005898:Glass / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D012823:Silicate Cement / Q000737:chemistry*; D013997:Time Factors
chemical_list: D003764:Dental Materials; D005899:Glass Ionomer Cements; C111282:dental polyglass; C009753:fiberglass; D012823:Silicate Cement