Fracture resistance of nonfiber versus fiber-reinforced composite resin restorations

Abstract Objective In-vitro evaluation of the fracture resistance of maxillary premolars weakened by MOD cavities restored with fiber-reinforced composite and nanohybrid composite. Materials and methods Twenty noncarious human maxillary premolars teeth were collected and mounted in acrylic resin blocks (2 mm below the cementoenamel junction). All specimens received standardized MOD cavities without proximal boxes. The pulpal floor will be at a depth of 2 mm from the deepest point fissure to the cavity floor and an isthmus width of 3 mm buccolingually. All specimens were divided equally into two groups (10 teeth each); group I: restored with fiber-reinforced composite GC Ever X posterior covered by a 0.5 mm layer of nanohybrid composite on the occlusal surface. Group II: restored with nanohybrid composite (Tetric-N-Ceram). All restored specimens were thermocycled then all groups were tested for fracture resistance using universal testing machine. Fracture analysis was performed under a stereomicroscope (×16), and the mode of fracture for each specimen was determined. All data were collected, tabulated, and statistically analyzed. Results The results showed that group I had the highest fracture resistance) 1516.6 ± 98.09(and group II had the lowest fracture resistance) 1132.5 ± 218.08(. The difference between two groups was statistically significant ( P < 0.05). Moreover, group I showed 70% had mode II of failure (cohesive fracture of the tooth structure) while in group II most specimens (60.0%) had mode IV of failure (complete fracture of the specimens). Conclusion The use of short fiber-reinforced resin composite as intermediate layer enhanced the fracture resistance of MOD composite restoration.