IADR Abstract Archives
Fracture Toughness of Bilayered Composite Structure with Short Fiber-reinforced Base
Objectives: Bilayered short fiber-reinforced (SFRC) composite restorations comprise SFRC base and veneering layer, usually direct composite resin (CR). The aim was to investigate the crack propagation and fracture resistance of this type of bilayered composite structure upon storage in water for 6 months.
Methods: Modified fracture toughness (FT) was evaluated using single-edge notched beam specimens (2.5x5x25 mm). The specimens (n=12) were water-stored at 37 degrees for 1 week (Group 1), 1 month (Group 2) and 6 months (Group 3). The SFRC (everX Posterior, GC Europe) was inserted in one increment with thickness of 2.0 mm and light-cured (Elipar S10, 3M ESPE) for 20 s in five separate overlapping portions. The veneering CR (A2, G-ænial Posterior, GC Europe) was then placed over the SFRC base in two increments (1.5 mm each). Prior light-curing the first layer (20 s/portion; 5 overlapping portions), a sharp and centrally located crack was produced by inserting a straight edged razor blade into the prefabricated slot, which extended to half the width of the mold (crack-tip located in CR). Upon storage, the specimens were tested in three-point bending mode in a universal material testing machine at a crosshead speed of 1.0 mm/min. Fracture propagation paths were analyzed with SEM. One-way ANOVA was used to analyze difference between the groups.
Results: The FT of bilayered composite structure with SFRC base did not change significantly (p>0.05) over the observation period of 6 months in water. The FT values (in MPam½) were 1.47 (±0.5), 1.41 (±0.2) and 1.40 (±0.4) for 1 week, 1 and 6 months respectively. None of the specimens broke into two halves.
Conclusions: The FT of bilayered composite structure remained stable regardless of the time of exposure in water. SFRC base deviated or arrested the crack propagation and enabled a ductile fracture.
Methods: Modified fracture toughness (FT) was evaluated using single-edge notched beam specimens (2.5x5x25 mm). The specimens (n=12) were water-stored at 37 degrees for 1 week (Group 1), 1 month (Group 2) and 6 months (Group 3). The SFRC (everX Posterior, GC Europe) was inserted in one increment with thickness of 2.0 mm and light-cured (Elipar S10, 3M ESPE) for 20 s in five separate overlapping portions. The veneering CR (A2, G-ænial Posterior, GC Europe) was then placed over the SFRC base in two increments (1.5 mm each). Prior light-curing the first layer (20 s/portion; 5 overlapping portions), a sharp and centrally located crack was produced by inserting a straight edged razor blade into the prefabricated slot, which extended to half the width of the mold (crack-tip located in CR). Upon storage, the specimens were tested in three-point bending mode in a universal material testing machine at a crosshead speed of 1.0 mm/min. Fracture propagation paths were analyzed with SEM. One-way ANOVA was used to analyze difference between the groups.
Results: The FT of bilayered composite structure with SFRC base did not change significantly (p>0.05) over the observation period of 6 months in water. The FT values (in MPam½) were 1.47 (±0.5), 1.41 (±0.2) and 1.40 (±0.4) for 1 week, 1 and 6 months respectively. None of the specimens broke into two halves.
Conclusions: The FT of bilayered composite structure remained stable regardless of the time of exposure in water. SFRC base deviated or arrested the crack propagation and enabled a ductile fracture.