fracture characteristics of fiber reinforced composite bars used to form rigid orthodontic anchorage units

objective : the aim of this study was to evaluate fracture characteristics of rigid two-tooth segments splinted with fiber reinforced composite (frc), with and without application of simulated masticatory forces. material and methods: in this experimental study, 80 extracted maxillary bicuspids were joined in pairs from the buccal aspect using frc. the specimens were divided into two groups. in group a, the fracture load of frc was measured. the 20 specimens of group b were initially loaded in a chewing simulator machine for 4×10 5 cycles to simulate a two-year chewing period. samples that withstood these loads were assessed for fracture load. the results were compared using student t-test. stereomicroscopic evaluation of fracture areas was performed to determine the fracture pattern. results: none of the specimens in group b failed during application of simulated masticatory forces, meaning that the survival rate was 100%. mean (standard deviation) of fracture loads in groups a and b were 195.80 (14.345) and 190.57 (24.027), respectively. no significant difference was found in mean fracture loads between the two groups. the overall fracture pattern was similar in both groups. conclusions: frc bars demonstrated sufficient durability to withstand chewing forces within the chewing simulation period. the fracture loads were higher than the mean mastication forces and remained almost unchanged after application of these forces.