Tricalcium silicate material (conventionally termed MTA cements) has been recently introduced in dentistry in order to provide dentin substitute for coronal and radicular pulp. Despite of number of advantages of MTA, its limitations cannot be overlooked.These drawbacks have been overcome by a new calcium silicate based material named biodentine which has good handling properties, short setting time and improved mechanical properties with excellent biocompatibility as well as a bioactive behavior.. In nut shell it is able to act as a promising dentin substitute in coronal and radicular portion of tooth(114).Hydraulic cements with bioactive properties due to the formationof apatite and calcite might have many important clinical applications indentistry, enhancing fast bone regeneration and pulp healing. Thesedata might explain the excellent clinical behavior reported for calcium silicate cements(115).The present study has been performed to determine sealing ability, remineralization capacity, solubility, water sorption and water leachable content of the newely introduced tricalcium silicate based material. Two commercially available cements were used in this study:One light cured glass ionomer cement (vitrebond)and one bioactive tricalcium silicate cement (biodentine). A total number of 31 specimens were prepared for this study; Six specimens for determining remineralization capacitythrough measuring apatite forming ability (bioactivity) which was investigated by evaluating the apatite formation on the material disks in the presence of a simulated body fluid by Scanning Electron Microscope (Field Emission Gun) attached with Energy Dispersive X-ray analysis Unit EDX.10 specimens for solubility and water sorption tests were performed according to ISO 6876, 2002. 15 specimens for water leachable content test, 10 specimens for biodentine and vitrebond for calcium release using an atomic absorption spectrophotometry and five specimens for vitrebond only for fluoride ion release using a fluoride ion selective electrode and a total number of 16 teeth were used to determine sealing efficiency of each material by measuring marginal leakage by a dye penetration test.For biodentine each capsule was mixed with five drops of the biodentine liquid. Mixing was done using a mechanical mixer for 30 seconds. On the other hand, for the vitrebond mixing was done by adding one drop of the liquid to two scoops of the powder. Mixing was done on a paper pad using a plastic spatula and cured by a light curing system for 30 seconds. All specimens were prepared according to manufacturer's instructions using split teflon molds with different dimensions according to each test specifications: The remineraliztion ability test specimens were prepared with dimensions of (8mm x 1.6mm), the solubility and water sorption specimens were prepared with dimensions of (20 mm x 1.5mm), the water leachable content test specimens were prepared with dimensions of (8mm x 1.6mm), the sealing ability test specimens were upper premolars teeth collected and stored in distilled water till the test procedures.Regarding sealing efficiency, it was found that biodentine showed statistically significantly lower mean marginal leakage scores and marginal gap results than vitrebond.Regarding remineralization capacity for biodentine at day 1,7 and 28 ,the high Ca/P values can be correlated withthe contribution of the formation of calcium carbonate (CaCO3) isomorphs (calcite and aragonite).while, for vitrebond,the Ca/P values of vitrebond can be correlated withthe contribution of the formation of calcium carbonate (CaCO3) isomorphs (calcite and aragonite) at day 1 and Ca-rich (carbonated) Apatitic , at day 7 and day 28. As for, solubility and water sorption it was found that biodentine showed statistically significantly lower mean values than vitrebond at day 1 as well as day 7.Finally, for water leachable content biodentine showed statistically significantly higher mean calcium release than vitrebond and for fluoride release, vitrebond showed the greatest amount of fluoride being released in the first 24 hours. Afterwards the fluoride release leveled from day 7 to day 28 and respectively.