Background: The most important change in the mechanical properties of endodontically-treated teeth is the reduction of fracture strength. The aim of the present study was to compare the fracture strength of teeth restored with bulk-fill composite, flowable bulk-fill composite and conventional composite resin in the presence or absence of fiber.Materials and Methods: In this laboratory study, 120 intact maxillary first premolar teeth were selected and placed in eight groups. The groups were designed with three types of composites (conventional, bulk-fill, flowable bulk-fill) with and without fiber and two negative control groups and positive, Mesio-occlusal-distal (MOD) cavity was prepared in all groups. After the endodontics, the composite of the same group was used in each group to restore the teeth by incremental method. All restorations were polished, mounted and tested by Universal testing machine. Results: The fracture strength in the fiber-reinforced bulk-fill composite group was significantly higher than the fiber-free group. The teeth restored with fiber-free composites had lower fracture strength. The fracture strength was the same in the samples treated with conventional and bulk-fill composite resins, and it was significantly lower in the samples treated with flowable bulk-fill composite than those treated with conventional and bulk-fill composites. There was a significant difference in fracture strength of fiber-reinforced composites.Conclusion: Tooth restoration reduces fracture strength. Fiber addition has no significant effect on increasing the fracture strength of composites. پرونده مقاله

Background: Composite resins undergo changes in properties due to various oral irritations over time. This study analyzed the effect of semi-nutritious liquids on the shear bond strength of repaired composite with universal bonding Materials and methods: This laboratory experiment used 80 samples of rectangular cubes made of Z250 composite. The samples were subjected to Thermocycling in an incubator and divided into four experi-mental groups, one control group, and stored in different solutions for seven days. After the aging process, the samples were roughened, bonding was applied, and a composite cylinder was placed on the previous composite. The bond strength was then calculated with an Instron device, and the data were analyzed using one-way ANOVA and Bonferroni's post hoc test (α=0.05). Results: Maximum average of bond strength in semi-nutrient liquids was recorded in descending order 25.53MPa for saliva , distilled water (20.24MPa), ethanol (18.04 MPa), citric acid (16.24 MPa), and Hep-tane (9.83 MPa), respectively. Conclusions: Artificial saliva yielded the highest average bond strength, while distilled water, ethanol, citric acid, and heptane resulted in decreasing bond strength. پرونده مقاله