Water Influence on Fracture Toughness of Fibre-Reinforced Composite

Fibre-reinforced composites (FRC) have been successfully utilized in dentistry for many years. Researchers reported the pre-impregnated fibre-reinforced composite significantly resists a higher load than the regular composite. The stability of the material in water is unknown. Objectives: This study was to compare the fracture toughness of two commercially available fibre-reinforced composites before and after water treatment. Methods: Two control groups (n=10) and four testing groups (n=20) of the FRC were fabricated following the manufacture's instruction. The samples were classified as: (1) EM (b or a: before or after water treatment): EverStic (StickTech Ltd/Finland) embedded with 3M composite (3M-ESPE/Germany); (2) ES (b or a): EverStic embedded with Sculpture® composite (Jeneric/Pentron Inc, Wallingford, CT ); (3) FS (b or a): FibreKor® embedded with Sculpture® composite; and (4) FM (b or a): FibreKor® embedded with 3M composite; (5): Sb: Sculpture® composite; (6): 3Mb: composite. All samples were fabricated in the same size (2x2x14mm) using a single template and tested by a Minature 3 point Bend Fixture on an Instron 5566 (Canton, MA). The control and "a" groups samples were immersed in water for three month at 22^oC before testing. Impregnation of fibres with composite was examined under a scanning electron microscope (SEM). The means forces at flexure were calculated and statistically evaluated utilizing ANOVA. Results: There was significant decrease in fracture strength after water treatment in every sample group: EMb (6.31±1.3), EMa (1.34±1.2); ESb (6.57±0.9), ESa (2.63±0.7); FSb (4.9±0.7), FSa (3.52±0.4); FMb (2.6±0.6), FMa (2.63±0.6); (p≤.05). The fracture strength after water treatment is stronger than the control group 3Ma (0.93±0.6), Sa (0.89±0.9). Conclusion: Water directly influences on fracture toughness of two commercial available fibre-reinforced composite. It significantly decreases the fracture strength of fibre-reinforced composite. Fibre-reinforced composites are stronger than the same composites without fibre reinforcement.