Role of Free-water Loss on Residual Strain and Fracture Predilection in Root Dentin: A Three-dimensional Digital Image Correlation Analysis

Free-water loss induced residual strain, with and without axial loading, and the mechanical effect of cyclic loading in fully hydrated and partially dehydrated root dentin were evaluated using 3D-Digital Image Correlation and Micro CT imaging. 2 hours of free-water loss resulted in the formation of residual compressive strain with areas of tensile strain localized to root canal and outer dentin. More residual compressive strain was observed in the apical dentin compared to the cervical dentin. More residual shear strain was observed in the outer dentin compared to the inner dentin. Axial loading resulted in an increase in the load-induced compressive strain in the direction perpendicular to dentinal tubules. Fully hydrated samples displayed a higher mean number of cycles to fracture with micro-cracks characteristic of toughness when compared to partially dehydrated samples. Free-water loss occurring in endodontically treated teeth may play a significant role in their predisposition to vertical root fractures.