title: Effects of fiber-glass-reinforced composite restorations on fracture resistance and failure mode of endodontically treated molars.
abstract: The study evaluated the fracture resistance and fracture patterns of endodontically treated mandibular first molars restored with glass-fiber-reinforced direct composite restorations.
  
  
  
  In total, 60 extracted intact first molars were treated endodontically; a mesio-occluso-distal (MOD) cavity was prepared and specimens were then divided into six groups: sound teeth (G1), no restoration (G2), direct composite restoration (G3), fiber-post-supported direct composite restoration (G4), direct composite reinforced with horizontal mesio-distal glass-fibers (G5), and buccal-palatal glass-fibers (G6). Specimens were subjected to 5000 thermocycles and 20,000 cycles of 45° oblique loading force at 1.3Hz and 50N; they were then loaded until fracture. The maximum fracture loads were recorded in Newtons (N) and data were analyzed with one-way ANOVA and post-hoc Tukey tests (p<0.05). Fractured specimens were analyzed with a scanning electron microscope (SEM).
  
  
  
  The mean static loads (in Newtons) were: G1, 831.83; G2, 282.86; G3, 364.18; G4, 502.93; G5, 499.26; and G6, 582.22. Fracture resistance did not differ among G4, G5, and G6, but was significantly higher than G3 (p=0.001). All specimens fractured in a catastrophic way. In G6, glass fibers inducted a partial deflection of the fracture, although they were not able to stop crack propagation.
  
  
  
  For the direct restoration of endodontically treated molars, reinforcement of composite resins with glass-fibers or fiber posts can enhance fracture resistance. The SEM analysis showed a low ability of horizontal glass-fibers to deviate the fracture, but this effect was not sufficient to lead to more favorable fracture patterns above the cement-enamel junction (CEJ).
  
  
  
  The fracture resistance of endodontically treated molars restored with direct composite restorations seems to be increased by reinforcement with fibers, even if it is insufficient to restore sound molar fracture resistance and cannot avoid vertical fractures.
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy. Electronic address: nicola.scotti@unito.it.
authors: Nicola
authors: N
authors: Scotti
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy.
authors: Alberto
authors: A
authors: Forniglia
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy.
authors: Riccardo Michelotto
authors: RM
authors: Tempesta
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy.
authors: Allegra
authors: A
authors: Comba
authors: Division of Cariology and Endodontology, School of Dentistry, University of Geneva, Rue Barthèlemy-Menn, Geneva, Switzerland.
authors: Carlo Massimo
authors: CM
authors: Saratti
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy.
authors: Damiano
authors: D
authors: Pasqualini
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy.
authors: Mario
authors: M
authors: Alovisi
authors: Department of Surgical Sciences, Dental School Lingotto, University of Turin, Via Nizza 230, Turin, Italy.
authors: Elio
authors: E
authors: Berutti
mesh_terms: D003188:Composite Resins; D003799:Dental Stress Analysis; D005898:Glass; D008963:Molar; D011176:Post and Core Technique; D014082:Tooth Fractures; D019553:Tooth, Nonvital
chemical_list: D003188:Composite Resins
keywords: Direct composite; Endodontically treated; Fractography; Fracture resistance; Glass-fiber