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Aim: To evaluate the effect of using two types of flowable resin composites and storage time on nano-leakage of repaired water aged resin composite. Materials and Methods: In total, 30 resin composite discs were prepared and stored in distilled water for 6 m. The discs were then randomly divided into 6 experimental groups (n=5/group) according to the two experimental factors of the study: Factor 1: Flowable composite, 3 groups (no-flowable, high-viscosity and low-viscosity flowable composites), and Factor 2; Storage time after repair, 2 groups (24 h and 6 m). Repair procedures were carried out using universal adhesive with and without the application of the flowable composite. After repair, half of the specimens were stored for 24 h and the other half were stored for 6 m in distilled water. After the recommended storage time, each disc was sectioned into 2 halves and each half was prepared for silver nitrate staining procedures to evaluate the nano-leakage under SEM. Three photomicrographs were taken for each half-slab, resulting in 30 photomicrographs/group, which were analyzed using ImageJ software. Data were evaluated using Kruskal-Wallis/Mann-Whitney test (P=0.05). Results: The use of flowable composite had no significant effect on nano-leakage (P=0.129), while storage time showed a statistically significant effect on nano-leakage (P < 0.0001). There was no statistically significant difference regarding the use of flowable resin composite either at 24 h or 6 m storage times (P > 0.05). There was a statistically significant difference between 24 h and 6 m storage periods for all experimental variables (P < 0.05). Conclusion: The two types of flowable composites were not able to prevent the uptake of silver nitrate at the composite/composite interface either after 24 h or 6 m.

This study aimed to evaluate the combined effect of fiber post in different Root canal tapers. Sixty lower first premolar human extracted teeth had been used in this study, teeth were randomly divided into 3 equal groups (n=20). Group I; where cleaning and shaping was done using Twisted File (TF) #25 taper 0.04. Group II; where cleaning and shaping was done using Twisted File (TF) #25 taper 0.06. Group III; where cleaning and shaping was done using Twisted File (TF) #25 taper 0.08. Each main group was randomly subdivided into 2 equal subgroups (10 each) according to the coronal restoration type. Subgroup A; where coronal cavities were filled with Composite core material Multicore Flow (Ivoclar Vivadent, Schaan, Liechtenstein) (MCF), Subgroup B; where the coronal cavities were restored with fiber reinforced composite posts (FRC) and MCF. The fracture resistance of all groups had been evaluated & analyzed using Two-Way ANOVA. Results showed that 0.08 taper had a significant negative effect on the fracture resistance of teeth with and without post than 0.04 taper while other variants had no any statistically significant effect on the fracture resistance of the tested samples. It has been concluded that, under limitations of this study, the degree of taper of the root canal preparation only affects mechanical properties of the tooth when it increases more than 0.06 taper, while wether a post is used or not is of no use in class I conservative access cavity preparation of lower first premolar teeth.