Effect of Fiber Layers on the Fracture Resistance of Fiber Reinforced Composite Bridges

The purpose of this in vitro study was to introduce the fiber reinforced composite bridges and evaluate the most suitable site and position for placement of fibers in order to get maximum strength. The study included 20 second premolars and 20 second molars selected for fabricating twenty fiber reinforced composite bridges. Twenty specimens were selected for one fiber layer and the remaining teeth for two fiber layers. In the first group, fibers were placed in the inferior third and in the second group, fibers were placed in both the middle and inferior third region. After tooth preparation, the restorations were fabricated, thermocycled and then loaded with universal testing machine in the middle of the pontics with crosshead speed of 1mm/min. Data was analyzed by Kolmogorov-Smirnov test, Independent sample t test and Kaplan-Meier test. Mode of failure was evaluated using stereomicroscope. Mean fracture resistance for the first and second groups was 1416±467N and 1349±397N, respectively. No significant differences were observed between the groups (P>0.05).In the first group, 5 specimens had delamintation and 5 specimens had detachment between fibers and resin composite. In the second group, there were 4 and 6 delaminations and detachments, respectively. There was no fracture within the fiber. In the fiber reinforced fixed partial dentures, fibers reinforce the tensile side of the connectors but placement of additional fibers at other sites does not increase the fracture resistance of the restoration.