Objectives: This study will analyze the modulus of elasticity of novel smart dentine replacement (SDR) and a flowable composite resin when used as a base material under composite restoration. Materials: 1. Smart Dentine Replacement (SDR) 2. X-flow (flowable composite) Methods: Forty eight specimens will be fabricated for elastic modulus test. The specimens will be divided into two groups, twenty four specimens of SDR and twenty four specimens of X-flow. Each group will be further divided according to the aging condition into three subgroups, each subgroup contain eight specimens. In which modulus of elasticity will be measured after 24 hrs and then measured after storage in distilled water for one month then measured after storage in distilled water for three months. Then the data will be statistically analysed. Results: Elastic modulus of both Surefil SDR and X-Flow increases with the increase in the storage period in distilled water. Conclusion: SDR has higher elastic modulus than X-Flow.