Dentine is a hydrated biological composite structure that forms the major bulk of human tooth. Previous studies on the biomechanical properties of root-filled teeth has tended to focus on the strength of dentine or whole teeth, and few attempts were made to investigate the biomechanical behavior of hydrated and dehydrated dentine. Objectives: This study aims to investigate the role of hydration on the stress-strain behavior of dentine. Methods: Digital moiré interferometry (DMI) was utilized for this purpose. DMI is an optic-based non-destructive, whole-field experimental technique that provides complete strain field information. In the first part of this study, the deformation patterns in the plane perpendicular to the long axis (lateral direction) and along the long axis of upper central incisors (axial direction) were examined. In the second part, the pattern of deformation on the dentine during dehydration and rehydration was determined. Results: It was observed from this study that the structural dentine demonstrated distinct strain gradients along the axial and lateral directions. The hydrated dentine displayed significant strains along the axial direction (P<0.01), and this response was more characteristic of a tough material. On the contrary, the dehydrated dentine showed strain response characteristic of a brittle material. A conspicuous difference in lateral strain was observed between the outer and inner dentine upon dehydration. Conclusions: These experiments highlight the role of hydration on the biomechanical behavior of the structural dentine. This study confirms the finding that hydration considerably influenced the mechanical behavior of dentine.