Shrinkage Strains in the Dentin of Endodontically Treated Teeth with Water Loss.

Abstract – Introduction Dehydration has been considered as a potential contributor to Vertical Root Fractures VRF after root canal treatment (RCT). A loss of water could cause embrittlement of dentin and detrimental shrinkage strains. Senior patients have the highest risk of VRF. In this study we characterized the spatial distribution in shrinkage of tooth roots with respect to donor age and prior RCT. Methods Single-rooted human teeth with and without prior RCT were collected from young (age 60 years) adults. Transverse slices were sectioned from the apical-, middle- and coronal-thirds of the roots and digital image correlation (DIC) was used to evaluate shrinkage during free convection. Crack initiation and growth analysis was performed via optical microscopy and bound water in dentin was characterized by Raman Spectroscopy. Results The rate of shrinkage was significantly higher (p≤0.05) in the apical third than in the middle and coronal thirds of all teeth, regardless of donor age. The highest shrinkage strain occurred in the apical-third of old donor teeth with prior RCT. In addition, the RCT treated old teeth suffered the highest percentage of water loss with dehydration. Cracks initiated from the root surface and extended towards the canal with loss of water and shrinkage. Conclusion The apical third undergoes significantly larger shrinkage strains with dehydration than the remainder of the root. Prior RCT exacerbates the extent of shrinkage, particularly in the teeth of seniors and after clinical function, which could increase the propensity for VRF.