title: Damage mechanics and load failure of fiber-reinforced composite fixed partial dentures.
abstract: OBJECTIVE
  Damage mechanics has been defined as the study of the initiation (initial failure) and accumulation of damage to and including rupture (final failure). This study was designed to evaluate the effect of increasing fiber-reinforced composite (FRC) substructure within a standardized fixed partial denture (FPD) model on the failure performance, in terms of damage mechanics.
  
  
  METHODS
  The two FRC restorative systems, Targis/Vectris (TV) (Ivoclar Vivadent) and EverStick (ES) (Stick Tech with Gradia, GC Corp.), were used to restore the molar FPD model (1.5 mm axial and 2.0 mm occlusal reduction). Templates were used to standardize substructure designs with 0, 18, 43, and 66% cross-sectional FRC volume fraction (V(FRC)) of fiber substructure. Specimens (n = 5) were homogenized at 29 points and stored for 1 week at 37 degrees C in distilled water. Specimens were luted with calcium hydroxide, then statically loaded until failure. Initial failure (IF), final failure (FF) and the mode of failure were recorded.
  
  
  RESULTS
  The lowest mean load to initial failure was 530 N (TV 18%) and the highest was 1208 N (ES 66%). Linear regression analysis calculated the Pearson's correlation coefficient (r) for the interactions between V(FRC) and IF (ES: r = 0.7879, TV: r = 0.6184), V(FRC) and FF (ES: r = 0.912, TV: r = 0.8152), and between IF and FF (ES: r = 0.892, TV: r = 0.7237). Unreinforced specimens universally fractured instantaneously.
  
  
  CONCLUSIONS
  The highest loads to initial and final failure were yielded by specimens with the highest cross-sectional V(FRC).
authors.affiliation: Division of Biomaterials and Biomechanics, Department of Restorative Dentistry, Oregon Health and Science University, Portland, 97239, USA. dyers@ohsu.edu
authors.forename: Scott R
authors.initials: SR
authors.lastname: Dyer
authors.forename: John A
authors.initials: JA
authors.lastname: Sorensen
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D002126:Calcium Hydroxide / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D000044:Dental Abutments; D003738:Dental Cements / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D019232:Dental Restoration Failure; D003779:Denture Design; D003830:Denture, Partial, Fixed; D005898:Glass / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012823:Silicate Cement / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; D005899:Glass Ionomer Cements; C470230:Gradia; C485628:Stick resin; C111282:dental polyglass; C496140:everStick; C009753:fiberglass; D012823:Silicate Cement; D019904:Polymethyl Methacrylate; D002126:Calcium Hydroxide