Fracture resistance of two different designs in fiber-reinforced composite restorations in mandibular anterior bridges: An in-vitro study

The purpose of this study was to assess the fracture resistance of two different designs of tooth preparation and fiber placement in fiber-reinforced composite restorations replacing a missing mandibular lateral incisor. Forty newly extracted human mandibular intact teeth (20 centrals and 20 canines) were selected for fabrication of twenty FRC inlay bridges. A box preparation design with straight fibers, and a slot design preparation with curved fibers were implemented. After preparation, the teeth were mounted in self-cured acrylic resin with 6.5 mm distance from each other. PDL was simulated with polyether material. After taking impressions with polyether material, the impressions were poured with dental stone. The two groups of bridges were fabricated and bounded to teeth with panavia F2. The cyclic load of 1.2×106×20N×1.66HZ was applied with 130O angle. The samples were stored in 37 Co water for seven days and then thermo cycled (2000 cyles, 5-55 oC). The fracture strength was tested by a universal testing machine (Instron 1195) at a speed of 1 mm/min. The mode of fracture was observed under stereomicroscope. The data was analyzed by using independent sample T-test. The mean fracture resistance for the box design and direct fiber group was 1411.07 N and in the slot and curved fibers group was 377.33 N. The group difference was statistically significant (P=0.012). It could be concluded that in fiber-reinforced composite restorations, box design with straight fiber has more fracture resistance than slot design with curved fiber.