title: Fracture Strength of Endodontically Treated Teeth Restored with Composite Overlays with and without Glass-fiber Reinforcement.
abstract: OBJECTIVE
  To evaluate the fracture strength and the failure mode of endodontically treated teeth restored with composite resin overlays with and without glass-fiber reinforcement.
  
  
  METHODS
  A total of 32 extracted molars were divided into four equal groups. In the NFR-NFRC (no foundation restoration, no fiber-reinforced composite) and NFR-FRC (no foundation restoration, fiber-reinforced composite) groups, only a 5-mm-thick composite resin layer sealed the pulp chamber floors, whereas in the FR-NFRC (foundation restoration, no fiber-reinforced composite) and FR-FRC (foundation restoration, fiber-reinforced composite) groups, a 3.0-mm foundation restoration was used. NFR-NFRC and FR-NFRC groups were restored with composite resin overlays, whereas NFR-FRC and FR-FRC groups were restored with fiber-reinforced composite resin overlays. All specimens were subjected to mechanical loading in a computer-controlled masticator and then the fracture resistance was evaluated. Differences in means were compared using two-way ANOVA and Tukey's test. The level of significance was set at ɑ = 0.05.
  
  
  RESULTS
  All specimens successfully completed the fatigue test. The least fracture-resistant group was NFR-FRC, exceeded by FR-NFRC, NFR-NFRC, and FR-FRC, in that order, with FR-FRC being the most fracture-resistant group. Statistically significant differences were detected between the pairs NFR-NFRC/FR-FRC (p = 0.001), NFR-FRC/FR-FRC (p = 0.001), and FR-NFRC/FR-FRC (p = 0.001). Eight vertical root fractures occurred in group FR-NFRC, six in group NFR-NFRC, four in group NFR-FRC, and none occurred in group FR-FRC.
  
  
  CONCLUSIONS
  Within the limitations of this in vitro study, the incorporation of glass fibers and the presence of a foundation restoration were found to increase the fracture resistance and can favorably influence the fracture mode.
authors.forename: Carlo
authors.initials: C
authors.lastname: Monaco
authors.forename: Antonio
authors.initials: A
authors.lastname: Arena
authors.forename: Roberto
authors.initials: R
authors.lastname: Scotti
authors.forename: Ivo
authors.initials: I
authors.lastname: Krejci
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000368:Aged; D000537:Aluminum Oxide / Q000737:chemistry; D001696:Biomechanical Phenomena; D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry*; D045662:Dental Etching / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000648:ultrastructure; D003799:Dental Stress Analysis / Q000295:instrumentation; D005898:Glass / Q000737:chemistry*; D006801:Humans; D007284:Inlays; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008875:Middle Aged; D011140:Polyurethanes / Q000737:chemistry; D011897:Random Allocation; D018915:Root Canal Preparation / Q000379:methods; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors; D014082:Tooth Fractures / Q000503:physiopathology*; D019246:Tooth Preparation / Q000379:methods; D014092:Tooth Root / Q000293:injuries; D019553:Tooth, Nonvital / Q000628:therapy*; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C444701:Filtek Z250; D008689:Methacrylates; D011140:Polyurethanes; D012821:Silanes; C009753:fiberglass; D014867:Water; C029824:urethane dimethacrylate luting resin; D000537:Aluminum Oxide