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Aim:The in-vitro study compared the shear bond strength (SBS) of three recently introduced dual-cure resin based core build-up materials namely ParaCore, FluoroCore, and MultiCore.Materials and Methods:One hundred twenty extracted permanent human mandibular molar teeth were taken and sectioned horizontally beneath the dentinoenamel junction to expose the coronal dentin. The specimens obtained were divided into three main groups based on the materials used and then further divided into four sub-groups based on time interval with ten samples each. The dentin surface was treated with the respective adhesives of the groups and then bulk filled with core build-up materials. The attained samples were than subjected to shear loading in Instron Universal Testing Machine. The data were tabulated and statistically analyzed using analysis of variance (ANOVA), Tukey's HSD, and Levene's test.Results:The mean SBS was highest in MultiCore at all time periods as compared to FluoroCore and ParaCore and was also higher at 48 h thermocycling in all three groups studied.Conclusion:MultiCore dual-cure resin based core build-up material showed the highest mean SBS as compared to FluoroCore and ParaCore. SBS was not negatively affected by thermocycling.

This in-vitro study evaluated and compared the flexural fatigue resistance for Hero Shapers, Hyflex CM, One Shape, Profile Vortex and Protaper Next rotary NiTi files. Method and materials: Total 25 rotary NiTi files allocated to each experimental group were tested in a simulated constructed apparatus with an angle of curvature 60°& radius of curvature 5 mm. Each experimental file was coated with EDTA gel and was placed in endodomotor handpiece with rubber stopper at support steel cylinder and its end between two shaping steel cylinders on the simulated apparatus. File was then rotated at 400 rpm, 2.5 N/cm torque and simultaneously digital stop watch was started. Time taken (in seconds) until the file got fractured was recorded. Results: Time taken to fracture ranged from 7 to 58 s in different groups. Analysis of variance show a statistically significant intergroup difference (p < 0.001). Tukey HSD test showed the significant differences. The Weibull modulus values ranged from 7.31 to 24.19. Conclusion: Cyclic flexural fatigue resistance was observed highest for Grp IV (Hyflex CM) and lowest for Grp I (Hero Shapers). Clinical significance: Hyflex CM rotary NiTi files can be used in curved root canals as they had superior resistance and long survival time which will be helpful in eliminating one of the reasons for file fracture (due to cyclic flexural fatigue) during the root canal treatment clinically where root canal possesses a sharp bend or curve.

Hence, it could be concluded that two-piece implants can be placed following one-stage surgical protocol as predictably as when two-stage surgical technique is followed.