The aim of this study was to evaluate the sealing ability and fracture resistance of the recently introduced calcium silicate bioceramic sealer, Smart Paste Bio used in association with propoints compared to the gold standard pairing in endodontic obturation; AH Plus resin sealer and Gutta-percha points.Fifty eight single-rooted mandibular premolars were used in this study. The teeth were decoronated, prepared using the ProTaper rotary system till F4 and obturated using single cone technique. The samples were divided randomly between the two main parts of the study. In the first part, the sealing ability test, twenty eight samples were used, while in the second part, fracture resistance test, thirty samples were employed. The samples of each part were then divided into four groups; two experimental groups and two control groups. Group A: Smart Paste Bio sealer + propoint PT F4.Group B: AH-plus resin sealer + Single gutta-percha F4.Group C: Negative control group.Group D: Positive control.Sealing ability test: All specimens in groups A, B and C were coated with two layers of nail varnish except the apical 2 mm, while the negative control group was completely sealed by the nail varnish till the apical foramen. Specimens were immersed in 2% methylene blue dye for 5 days. After being removed from the dye, the specimens were washed under tap water and dried. All roots were carefully sectioned perpendicular to the long axis with a diamond disc. Three sections of each root were made at 2 mm, 4 mm and 6 mm from the apex. Samples were studied under the digital microscope, magnification 50X for evaluation of dye penetration between the root canal filling and radicular dentin at three levels; apical, middle and coronal. Each specimen was given a score for dye penetration. The data of dye penetration obtained by digital microscope evaluation were considered for statistical analysis.Pearson's chi-square test, Mann-Whitney test and Kruskal-Wallis test were used for comparison among the different subgroups. The results revealed that Smart Paste Bio /propoints (group A) and AH-plus /gutta-percha (group B) showed no dye penetration in the coronal and middle thirds. AH-plus /gutta-percha showed significantly greater dye penetration in the apical third than Smart Paste Bio /Propoints.Fracture resistance test:The roots were mounted in acrylic blocks. The acrylic blocks including the roots were mounted on the lower fixed compartment of the Universal Testing Machine. The upper plate of the machine included a metal rod was mounted directly over the canal opening of each root, which was subjected to a slowly increasing vertical load (1 mm/min) until the fracture occurred. The load at failure values were recorded in Newtons. Values of the fracture resistance test denoting the mean and standard deviation (SD) of the maximum load specimens withstand till fracture were statistically analyzed. One-way ANOVA test was used for comparison among the different subgroups. The results showed that there was no statistical significance between Smart Paste Bio /Propoints group and AH-plus /gutta-percha group. Both groups reinforced the roots and showed mean fracture resistance comparable to the specimens that were not instrumented preserving its whole dentin thickness in the negative control group.Conclusions: From the results of this study, it could be concluded that:1.None of the evaluated obturation systems was able to completely prevent the dye penetration.2.Smart Paste Bio /Propoints pairing were more efficient in sealing ability than AH-plus /gutta-percha particularly at the apical third.3.Smart Paste Bio system and AH-plus system showed comparable fracture resistance efficacy that was not statistically different from the un-instrumented roots.Recommendations: 1.Calcium silicate-based sealers associated with the hydrophilic polymeric propoints could be recommended as an efficient material for root canal obturation.2.Further studies are recommended to test the sealing ability and fracture resistance of Smart Paste Bio when used in association with gutta-percha points.3.Further studies are recommended to test the retreatability of Smart Paste Bio /propoints to assess the feasibility of its removal when re-treatment is required.