title: Fracture characteristics of fibre reinforced composite bars used to provide rigid orthodontic dental segments.
abstract: BACKGROUND
  Fibre reinforced composites (FRC) can be used to join teeth as a rigid unit for anchorage purposes and/or for tooth movement. The utility of FRCs for these applications depends on the fracture characteristics and durability of the material under masticatory loads.
  
  
  OBJECTIVE
  To evaluate the effect of simulated masticatory loads on the fracture characteristics of FRC bars joining two bicuspids.
  
  
  METHODS
  Eighty extracted maxillary bicuspids were used. Pairs of bicuspids were joined with FRC bars on the buccal surfaces. The specimens were divided into two equal groups. In group A the fracture loads of the FRC bars were measured, and in group B the specimens were placed in a simulator and subjected to 4x10(5) chewing cycles, simulating a 2-year period of mastication. At the conclusion of this test the fracture loads of the FRC bars were measured in the intact specimens. All specimens were examined stereomicroscopically to determine the fracture pattern.
  
  
  RESULTS
  There were no bond failures in group B during the simulated masticatory forces. The mean fracture loads in groups A and B were 195.8 N and 190.6 N, respectively. Stereomicroscopic examination showed that most fractures occurred at the enamel-composite interfaces in both groups. There were no significant differences between the groups in the fracture loads and fracture patterns.
  
  
  CONCLUSIONS
  Fibre reinforced composite bars bonded to bicuspids had sufficient durability to withstand the loads simulating a 2-year period of function. The fracture loads and fracture patterns of the FRC bars were not affected by the loads exerted by the simulator.
authors.affiliation: Dental Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. dr_s_tahmasbi@yahoo.com
authors.forename: Soodeh
authors.initials: S
authors.lastname: Tahmasbi
authors.forename: Farzin
authors.initials: F
authors.lastname: Heravi
authors.forename: Saied Mostafa
authors.initials: SM
authors.lastname: Moazzami
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001641:Bicuspid / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003799:Dental Stress Analysis / Q000379:methods*; D008422:Materials Testing / Q000379:methods; D011140:Polyurethanes / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes